Consensus statement

IOC consensus statement: dietary supplements andthe high-performance athlete
Ronald J Maughan,1 Louise M Burke,2,3 Jiri Dvorak,4 D Enette Larson-Meyer,5Peter Peeling,6,7 Stuart M Phillips,8 Eric S Rawson,9 Neil P Walsh,10 Ina Garthe,11Hans Geyer,12 Romain Meeusen,13 Lucas J C van Loon,3,14 Susan M Shirreffs,1Lawrence L Spriet,15 Mark Stuart,16 Alan Vernec,17 Kevin Currell,18 Vidya M Ali,19Richard GM Budgett,20 Arne Ljungqvist,21 Margo Mountjoy,22,23 Yannis P Pitsiladis,19
Torbjørn Soligard,20 Uğur Erdener,19 Lars Engebretsen20
For numbered affiliations see
end of article.
Correspondence toProfessor Ronald J Maughan,
School of Medicine, St Andrews
University, St Andrews, UK;​ronmaughan@​st-​andrews.​ac.​uk
Accepted 3 February 2018

Abstract
Nutrition usually makes a small but potentiallyvaluable contribution to successful performance in elite
athletes, and dietary supplements can make a minor
contribution to this nutrition programme. Nonetheless,supplement use is widespread at all levels of sport.
Products described as supplements target different
issues, including (1) the management of micronutrient
deficiencies, (2) supply of convenient forms of energy andmacronutrients, and (3) provision of direct benefits toperformance or (4) indirect benefits such as supporting
intense training regimens. The appropriate use of some
supplements can benefit the athlete, but others may
harm the athlete’s health, performance, and/or livelihood
and reputation (if an antidoping rule violation results). A
complete nutritional assessment should be undertaken
before decisions regarding supplement use are made.
Supplements claiming to directly or indirectly enhance
performance are typically the largest group of products
marketed to athletes, but only a few (including caffeine,creatine, specific buffering agents and nitrate) have goodevidence of benefits. However, responses are affectedby the scenario of use and may vary widely between
individuals because of factors that include genetics, themicrobiome and habitual diet. Supplements intended
to enhance performance should be thoroughly trialled
in training or simulated competition before being usedin competition. Inadvertent ingestion of substances
prohibited under the antidoping codes that govern
elite sport is a known risk of taking some supplements.
Protection of the athlete’s health and awareness ofthe potential for harm must be paramount; expert
professional opinion and assistance is strongly advised
before an athlete embarks on supplement use.

Introduction►► http://​dx.​doi.​org/​10.​1136/​
bjsports-​2018-​099199

To cite: Maughan RJ,
Burke LM, Dvorak J,
et al. Br J Sports Med
2018;52:439–455.

Dietary supplements are used by athletes at all levelsof sport, reflecting the prevalence of their use in thewider society. About half of the adult US population uses some form of dietary supplements,1 andalthough there are regional, cultural and economic
differences, a similar prevalence is likely in manyother countries. Athletes describe a range ofdifferent reasons for their supplement choices,2 andproducts that fit the description of ‘supplement’
can target various roles within the athlete’s performance plan. These include the maintenance ofgood health by contributing to the required intakeof specific nutrients, the management of micronutrient deficiencies, and the provision of energy
and macronutrient needs that might be difficult toachieve through food intake alone. Other specificuses of supplements reported by athletes include
direct performance enhancement or the indirect
benefits that arise from the provision of support
for hard training, the manipulation of physique, thealleviation of musculoskeletal pain, rapid recovery
from injury and enhancement of mood.
Some sporting bodies now support the pragmaticuse of supplements that have passed a risk-versus-benefit analysis of being effective, safe andpermitted for use, while also being appropriate to
the athlete’s age and maturation in their sport. This
review summarises the issues faced by high-performance athletes and their support team (coach,trainer, nutritionist, physician) when considering
the use of supplements, with the goal of providing
information to assist them to make informed
decisions.

What is a supplement?

There is no single definition, either legal or within
nutritional science, of what constitutes a dietary
supplement. The US Congress, for example, inframing the 1994 Dietary Supplement Health and
Education Act (DSHEA; https://​ods.​od.​nih.​gov/​
About/​DSHEA_​Wording.​aspx), described a dietary
supplement as:‘…a product, other than tobacco, which is used inconjunction with a healthy diet and contains one ormore of the following dietary ingredients: a vitamin,mineral, herb or other botanical, an amino acid, a
dietary substance for use by man to supplement
the diet by increasing the total daily intake, or aconcentrate, metabolite, constituent, extract, or
combinations of these ingredients’.3

This definition is unsatisfactory, as it depends onwhether or not a ‘healthy diet’ is consumed. For
the purposes of this overview, we define a dietary
supplement as the following:
A food, food component, nutrient, or non-foodcompound that is purposefully ingested in addition
to the habitually consumed diet with the aim ofachieving a specific health and/or performance
benefit.

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027   439

Consensus statement
Furthermore, we recognise that dietary supplements come inmany forms, including the following:
1. functional foods, foods enriched with additional nutrients orcomponents outside their typical nutrient composition (eg,mineral-fortified and vitamin-fortified, as well as nutrientenriched foods)
2. formulated foods and sports foods, products providing
energy and nutrients in a more convenient form than normal
foods for general nutrition support (eg, liquid meal replacements) or for targeted use around exercise (eg, sports drinks,
gels, bars)
3. single nutrients and other components of foods or herbal
products provided in isolated or concentrated forms
4. multi-ingredient products containing various combinations of
those products described above that target similar outcomes.

Prevalence of, and rationale for, use by athletesWith such widespread use of supplements in the general population and with the specific focus of athletes on achieving peak
performance, it is not surprising that a high prevalence of supplement use is reported in most surveys of athletes.4 Comparisons
between surveys are confounded by numerous factors: theseinclude differences in the definition of what constitutes a dietary
supplement; ability to capture irregular use; inappropriate
sample selection; and the use of non-validated and non-standardised survey instruments.5 Nevertheless, surveys generally
suggest that supplement use:
1. varies across different sports and activities
2. increases with level of training/performance
3. increases with age
4. is higher in men than in women
5. is strongly influenced by perceived cultural norms (bothsporting and non-sporting).
Although athletes often consume supplements to takeadvantage of intended/claimed effects or benefits, a range ofmotives underpin supplement use.5 For example, athletes use
supplements:
1. to correct or prevent nutrient deficiencies that may impair
health or performance
2. for convenient provision of energy and nutrients around an
exercise session
3. to achieve a specific and direct performance benefit incompetition
4. to gain a performance improvement indirectly accrued fromoutcomes such as allowing more effective training (ie, higher
intensity, greater volume), better recovery from training
sessions, optimising mass and body composition, or reducing
risks of injury and illness
5. for financial gain (sponsorship) or because products areprovided free of charge
6. as a ‘just in case’ insurance policy
7. because they know or believe that other athletes/competitors
are using the supplement(s).
Some supplements may be used for multiple functions. Zinc,
for example, may be taken with the aim of promoting woundhealing and tissue repair,6 or reducing the severity and duration of the symptoms of an upper respiratory tract infection.7
Carbohydrate supplements are used to enhance performance inmany events via the provision of fuel substrate,8 to support theimmune system9 or to improve bioavailability of other supplements, for example, creatine.10 Similarly, creatine supplementation may directly enhance performance in strength and power
events, and can assist in training harder, gaining lean body mass440

or maintaining lean mass during periods of immobilisation
after injury.11–13 Decisions on supplement use therefore needto consider both the context of use and the specific protocol
employed.

Assessing the evidence base for supplement use

Supplements target a range of scenarios of use, so different
approaches are needed to assess their effectiveness. Supplements
aimed at correcting nutrient deficiencies need to be judged on
their ability to prevent or treat suboptimal nutrient status, withthe benefit accruing from the removal of the associated impairment of health, training capacity or performance. The effectiveness of sports foods might be hard to isolate when they areused within the general diet to meet everyday energy needs andnutrient targets. However, benefits may be more easily detected
when they are specifically consumed before, during or after an
event or training session to provide nutrients that are limitingfor performance (eg, to provide fuel for the muscle or brain) or
to defend homeostasis (eg, by replacing water and salt losses).
Performance-enhancing supplements, which are claimed toachieve direct or indirect benefits, pose a greater challenge interms of a sound evidence base. With only a few exceptions,
there is a scarcity of research, and many of the available studies
are not of sufficient quality to warrant their application to elite
athletes.
Substantiating the claims made about performance supplements and sports foods is difficult.14 To various audiences, ‘proof ’comes in different forms. Figure 1 provides a proposed hierarchical model of the relative strength of the evidence provided bydifferent information sources. However, most of the information
around supplement efficacy in sport comes from models withthe lowest rigour: anecdotes/observations from athletes; andscientific or mechanistic hypotheses that explain how a supplement might target a critical/limiting factor in performance, butwith little to no evidence. Systematic reviews and meta-analyses,
which synthesise the outputs of many studies to yield a conclusive statement of efficacy in a broad sense, are at the top of
the evidence hierarchy. While these summaries help to provide
information about the general use of performance supplements,
scientific trials that are properly controlled and well-conducted
provide the basis for these reviews as well as an opportunity toaddress more specific questions about supplement applications.
Thus, meta-analyses are a reflection only of the quality andquantity of the studies that are available for review, and may also
be influenced by the inclusion and exclusion criteria applied tothe available data.
The ‘gold standard’ for investigating the effects of supplements on sports performance is the prospective, randomised,
controlled scientific trial, in which subjects are randomly allocated to receive either an experimental or placebo treatment(ideally in a double-blind manner) or crossed over to receive
both treatments in counterbalanced order, under standardised
conditions. Practical issues may cause some variations to ideal
design, but sports scientists are encouraged, if they wish theirresults to be applicable to athletes in competition, to ensure that
their studies include the following:
1. an adequate sample size and appropriate participantcharacteristics (eg, event, training status, calibre) to allow theresults to have statistical power and to be applicable to highperformance athletes
2. mimicking, as far as possible, the conditions (eg, environment, nutrition preparation, event strategies) that exist in
real-life competition

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

Consensus statement

Figure 1

Hierarchy of evidence used to establish good practice focused on the issue of nutritional supplements.

3. standardisation, to the extent that is possible, of variables
that might influence the results (eg, pretrial exercise anddiet, environmental conditions, external encouragement
or distraction)—it is recognised that this conflicts to someextent with (2) above, and will limit the situations in which
the results can be applied
4. use of a protocol of supplement use (eg, specific product,
dose and timing of intake) that is likely to optimise any effects
5. an independent verification of the contents of the supplement under investigation to ensure that the product is truly
unadulterated, both to ensure the integrity of the study andto avoid inadvertent doping positives if the subjects areathletes
6. verification that the supplement was taken and induced abiological response (eg, via muscle, blood, urine or saliva
sampling)
7. a performance protocol that is valid and sufficiently reliable
to detect small but potentially meaningful changes/differences in performance outcomes
8. interpretation of results in light of the limitations of thestudy design and the change that would be meaningful toreal-life sport.
Given the specificity of the information that is required bysome athletes and their support staff to assess the effectivenessof a supplement (eg, related to a targeted event and its conditions, the specific individual, the combination with other performance strategies), it is unreasonable to expect that definitive
evidence will always be available. Issues that are particularly
under-researched and should be considered of high priority
include measurement of performance in the field or under ‘reallife’ conditions, investigation of the combined use of a numberof supplements, and the repeated use of supplements as mightoccur in multiday competition or when heats and finals occur
close together. Scenarios that fall outside the scope of the available literature or practical research design may need to be interrogated by individual or small group case studies. Recommended
methodologies for these studies include repeated baseline performances before the introduction of the supplement, or an alternating series of presentation and absence of the supplement.15
For the purposes of this overview, we rely primarily on studiesof healthy adults that are relevant to athletes. We recognise thatdata from studies of elite athletes are almost entirely absent. We
also recognise that mechanistic studies on animal and cell culture
models are useful in identifying mechanisms, but a mechanism
is not necessary to demonstrate an effect that may be meaningful to an athlete: what we think today to be the mechanism
by which enhancement of performance or health occurs might
be proved wrong by later studies. It must also be recognised thatan individual’s habitual diet can affect gene expression and theirmicrobiota, and these in turn can affect response to supplementation. While the variation in the genome between individuals is
less than 0.01%, the variation in microbiota is significant (80%–90%), and emerging data suggest that both these factors could
affect athletic performance.16 17 The following sections present
an overview of the use of supplements to address different roles
in sports nutrition, first by identifying the principles of use andthen by examining some of the specific products that have agood or emerging evidence base to support this situation-specific use by athletes.

Supplements used to prevent or treat nutrient deficiencies

Many micronutrients play an important role in the regulation of processes that underpin sports performance, ranging
from energy production to the manufacture of new cells andproteins. A frank deficiency of one or more of these nutrients may lead to a measurable impairment of sports performance—either directly or by reducing the athlete’s ability to
train effectively (eg, iron deficiency anaemia) or to stay freefrom illness or injury (eg, impact of vitamin D deficiency onbone health). Athletes are not immune to the inadequate eating
practices or the increased nutrient loss/requirements found insome members of the general population and may even be at
greater risk of deficiencies because of increased nutrient turnover or increased losses. A further challenge is the occurrenceof subclinical deficiencies that may be both hard to assess(ie, they lack a clear metric or universal threshold of what is‘adequate’) as well as being subject to debate about whether
there is an ‘optimal’ level for performance that differs fromthe usual classification systems of nutrient status (deficiency/
subclinical deficiency/normal). When suboptimal nutritional
status is diagnosed, the use of a nutrient supplement to reverse

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

441

Consensus statement
Table 1

Examples of micronutrients often requiring supplementation in athletes (see Larson-Meyer et al18 for additional information)

Micronutrient Overview

Diagnosis and outcomes of insufficiency

Protocols and outcomes of supplementation

Vitamin D

No consensus over the serum 25-hydroxyvitamin D Supplementation of between 800 IU and 1000–2000 IU/day is
It is important in the regulation ofconcentration (the marker of vitamin D status) that recommended to maintain status for the general population.
gene transcription in most tissues, soinsufficiency/deficiency affects many body defines deficiency, insufficiency, sufficiency and a Supplementation guidelines are not yet established in athletes.
tolerable upper limit.
systems.42
Short-term, high-dose supplementation which includes 50 000
Many athletes are at risk of insufficiency The need to supplement depends on UVB exposure IU/week for 8–16 weeks or 10 000 IU/day for several weeks may
43
at various times throughout the year.
and skin type.
be appropriate for restoring status in deficient athletes. Carefulmonitoring is necessary to avoid toxicity.44

Iron

Suboptimal iron status may result fromlimited iron intake, poor bioavailability
and/or inadequate energy intake, or
excess iron need due to rapid growth,high-altitude training, menstrual blood
loss, foot-strike haemolysis, or excess
losses in sweat, urine or faeces.45

Several measures performed simultaneously
provide the best assessment and determine thestage of deficiency. Recommended measures:
serum ferritin, transferrin saturation, serum
iron, transferrin receptor, zinc protoporphyrin,
haemoglobin, haematocrit and mean corpuscularvolume.46

Calcium

Avoidance of dairy products and othercalcium-rich foods, restricted energy
intake and/or disordered eating increases
risk of suboptimal calcium status.45

There is no appropriate indicator of calcium status. Calcium intakes of 1500 mg/day and 1500–2000 IU vitamin D
Bone mineral density scan may be indicative
are recommended to optimise bone health in athletes with lowof chronic low calcium intake, but other factors
energy availability or menstrual dysfunction.45
including suboptimal vitamin D status anddisordered eating are also important.

Athletes who do not maintain adequate iron status may need
supplemental iron at doses greater than their RDA (ie, >18 mg/
day for women and >8 mg/day for men). Athletes with irondeficiency require clinical follow-up, which may include
supplementation with larger doses of oral iron supplementation
along with improved dietary iron intake.45 Numerous oral ironpreparations are available and most are equally effective as longas they are taken.47 High-dose iron supplements, however, should
not be taken unless iron deficiency is present.

Note: Indiscriminate supplementation with any of the above nutrients is not recommended. Deficiencies should first be identified through nutritional assessment, which includes
dietary intake and the appropriate blood or urinary marker, if available.17

or prevent further deficiencies can contribute to the overall
treatment plan.
Nutritional assessment of an athlete involves systematic
protocols that obtain, verify and interpret evidence of nutrition-related problems, as well as their causes and significance.
A complete assessment should ideally include a detailed medical
and nutritional history, diet evaluation, anthropometry and bodycomposition analysis, and biochemical testing.18 Unlike the ad
hoc use of nutrient supplements taken by athletes as an insurance
policy, this nutritional assessment should ensure that the athlete:
1. can address the factors that led to the nutrient deficiency,
including ensuring that the athlete’s nutrition plan isadequate in energy, macronutrients and micronutrients
2. would benefit from an acute or chronic period of supplementation to correct and/or prevent a nutrient deficiency and canunderstand the appropriate supplementation protocol
3. is not at risk for health issues associated with supplement use,
including interactions with prescription or over-the-counter
medications
4. has a baseline assessment against which future measures toassess progress can be compared.
Nutrients that often need to be supplemented under thesecircumstances include iron, calcium and vitamin D (table 1).
Iodine (for those living in areas with low levels of iodine in foods
or not using iodised salt), folate (for women who might become
pregnant) and vitamin B12 (for those following a vegan or nearvegan diet) supplementation may be warranted in these population groups, but these considerations do not apply specificallyto athletes.

Supplements (sports foods) used to provide a practical formof energy and nutrients

Sports nutrition guidelines provide clear recommendations fortargeted intake of energy and nutrients in a variety of contexts.
In some situations, it is impractical for an athlete to consume‘everyday’ or normal foods to meet their nutrition goals due
to issues around preparation or storage, ease of consuming thefoods due to training schedules, gut comfort, or the challengeof meeting nutrient targets within the available energy budget.
442

In these cases, sports foods can provide a convenient, althoughusually more expensive, alternative option for meeting thesenutrient goals. Table 2 provides an overview of products that fit
this description and their more common evidence-based uses.

Supplements that directly improve sports performance

A few performance-enhancing supplements might, at the present
time, be considered to have an adequate level of support tosuggest that marginal performance gains may be possible. These
supplements include caffeine, creatine (in the form of creatine
monohydrate), nitrate, sodium bicarbonate and possibly also
Beta-alanine. The mechanisms of action, typical dose, potential performance benefits and known side effects of each ofthese supplements are summarised in table 3. Performance-enhancing supplements should be considered only where a strong
evidence base supports their use as safe, legal and effective,
and ideally after adequacy of sports nutrition dietary practices
is ensured. Whenever possible, supplements should be trialledthoroughly by the athlete in training that mimics the competition milieu as closely as possible before committing to use in acompetition setting. Athletes should do a careful risk analysis tosee if the marginal gains would outweigh the risk of inadvertent
doping due to contamination.

Supplements that improve performance indirectly

Many dietary supplements claim to enhance performance indirectly—by supporting the athlete’s health, body composition,and their ability to train hard, recovery quickly, adapt optimally,
avoid or recover from injury, and tolerate pain or soreness.
Illness is a major problem for athletes if it interrupts trainingor occurs at a critical time, such as during a selection event or amajor competition. Susceptibility to illness is increased in situations where athletes are involved in a high volume of training orcompetition, and either intentionally or unintentionally experience deficits in energy intake (eg, weight loss diets), macronutrient intake (eg, train-low or sleep-low-carbohydrate) andmicronutrient status (eg, vitamin D insufficiency in the winter).19
Athletes might benefit from nutritional supplements to support

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

Consensus statement
Table 2

Summary of common sports foods and functional foods used by athletes.

Sports foodForm

Typical composition

Common sports-related use

Sports drink

Powder or ready to drink liquid

5%–8% CHO
10–35 mmol/L sodium
3–5 mmol/L potassium

Simultaneous delivery of fluid+CHO during exercise
Postexercise rehydration and refuelling

Energy drink

Ready-to-drink liquid orconcentrated shot

Carbohydrate, especially in typical ready-to-drink
Pre-exercise caffeine supplement
varieties
Carbohydrate and caffeine intake during exercise
Caffeine
Note: may contain taurine, B vitamins and otheringredients with variable supporting evidence and somelevel of concern

Sports gel or sports
confectionery

Gel: 30–40 g sachets confectionery: ~25 g CHO per sachet or ~5 g CHO per confectionery
jelly-type confectionery (generally in piece
pouch of ~40–50 g)
Some contain caffeine or electrolytes

Carbohydrate intake during exercise

Electrolyte
replacement
supplements

Powder sachets or tablets

Rapid rehydration following dehydration undertaken forweight-making
Replacement of large sodium losses during ultraendurance activities
Rapid postexercise rehydration following moderate tolarge fluid and sodium deficits

Protein supplement

Powder (mix with water or milk) or Provides 20–50 g protein in a single serve from highready-to-drink liquid
quality types of animal (whey, casein, milk, egg) or
Protein-rich bar, usually low in CHO vegetable (eg, soy) origin
Note: may contain other ingredients, some of which
are not evidence-based and may increase the risk ofcontamination

Postexercise recovery following key training sessions or
events where adaptation requiring protein synthesis is
desired
Achievement of increase in lean mass during growth or
response to resistance training
Portable nutrition for busy schedule or travel

Liquid meal
supplement

Powder (mix with water or milk) or
ready-to-drink liquid

1–1.5 kcal/mL: 15%–20% protein and 50%–70% CHO
Low to moderate fat
Vitamins/minerals: 500–1000 mL supplies RDI/RDAs

Supplement high-energy diet (especially during heavy
training/competition or weight gain)
Low-bulk meal replacement (especially pre-event meal)
Postexercise recovery (CHO and protein)Portable nutrition for busy schedule or travel

Sports bar

Bar

40–50 g CHO
5–10 g protein
Usually low in fat and fibre
Vitamins/minerals: 50%–100% of RDA/RDIs
Note: may contain other ingredients, some of which
are not evidence-based and may increase the risk ofcontamination

CHO source during exercise
Postexercise recovery—provides CHO, protein andmicronutrients
Portable nutrition for busy schedule or travel

50–60 mmol/L sodium
10–20 mmol/L potassium
Typically, low carbohydrate (2–4 g/100 mL)

Protein-enhanced food Milk, yoghurt, ice cream, cereal bars Increased protein content from normal food variety
and other food forms
achieved by adding protein sources or filtration ofwater from productTypically allows normal portion to provide ~20 gprotein to meet sports nutrition target

Value-added food able to achieve protein target for
postexercise use or to improve protein content of othermeals and snacks in an athlete’s diet

CHO, carbohydrate.

immunity in these scenarios and at other times when they are
either susceptible to infection (eg, during the common coldseason and after long-haul travel) or suffering from an infection. Table 4 summarises evidence for some of the commonly
promoted ‘immune supportive’ supplements, noting that themost promising candidates to assist in the prevention or treatment of upper respiratory symptoms are vitamin D and probiotics. Vitamin C during periods of heavy exertion and zinclozenges at the onset of symptoms may be useful, but high dosesof single antioxidants, particularly vitamins C and E, may blunt
exercise-induced training adaptations.20–22 Probiotic supplementation may reduce the incidence of travellers’ diarrhoea
and gastrointestinal infection. Cochrane reviews have noted thelow quality of many studies on nutritional supplements that areclaimed to support immunity; specifically, small samples, poor
controls and unclear procedures for randomisation and blinding
were commonplace.23 24 Clearly, there is a pressing need for
randomised controlled trials in high-level athletes with sufficientparticipant numbers, rigorous controls and procedures, appropriate supplementation regimens, and clinically meaningfulmeasures of immunity.

Supplements that assist an athlete to train harder, recover more
quickly and prevent injury, or accelerate return to play wheninjury does occur can obviously enhance the athlete’s preparation and, indirectly, their competition outcomes. Many products claim to provide benefits of this nature; table 5 summarises
the evidence for some of the most popular compounds. Finally,
the manipulation of body composition, including gaining lean(muscle) mass and reducing body fat levels, can contribute toperformance in many events. This explains the large numberof ‘weight gainers’ and ‘fat burners’ in the general and sports
supplement market, although many of these are prohibited in
sport. Protein is considered to be the premier ingredient inweight gain-promoting supplements, and evidence-based reviews
conclude that protein is effective at promoting lean mass gain
when combined with resistive exercise.25 Evidence of efficacy
for ‘fat burning’ supplements is far from conclusive, however,and there is a complete absence of evidence for the effectivenessof the vast majority of supplements marketed in this category.
Table 6 summarises the evidence for some of the most common
ingredients or products of this type.25

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

443

Consensus statement
Table 3

Supplements with good to strong evidence of achieving benefits to performance when used in specific scenarios

Caffeine
Overview

Caffeine is a stimulant that possesses well-established benefits for athletic performance across endurance-based situations, and short-term,supramaximal and/or repeated sprint tasks.

Mechanism

Adenosine receptor antagonism; increased endorphin release; improved neuromuscular function; improved vigilance and alertness; reduced theperception of exertion during exercise29 48

Protocol of use

3–6 mg/kg of body mass (BM), in the form of anhydrous caffeine (ie, pill or powder form), consumed ~60 min prior to exercise49
Lower caffeine doses (<3 mg/kg BM, ~200 mg), provided both before and during exercise; consumed with a CHO source48

Performance Impact

Improved endurance capacity such as exercise time to fatigue50 and endurance-based time-trial (TT) activities of varying duration (5–150 min),across numerous exercise modalities (ie, cycling, running, rowing and others)49
Low doses of caffeine (100–300 mg) consumed during endurance exercise (after 15–80 min of activity) may enhance cycling TT performance by
3%–7%.51 52
During short-term, supramaximal and repeated sprint tasks, 3–6 mg/kg BM of caffeine taken 50–60 min before exercise results in performancegains of >3% for task completion time, mean power output and peak power output during anaerobic activities of 1–2 min in duration,53 and of
1%–8% for total work output and repeat sprint performances during intermittent team game activity.54 55

Further considerations andpotential side effects

Larger caffeine doses (≥9 mg/kg BM) do not appear to increase the performance benefit,56 and are more likely to increase the risk of negativeside effects, including nausea, anxiety, insomnia and restlessness.29
Lower caffeine doses, variations in the timing of intake before and/or during exercise, and the need for (or lack thereof) a caffeine withdrawal
period should be trialled in training prior to competition use.
Caffeine consumption during activity should be considered concurrent with carbohydrate (CHO) intake for improved efficacy.52
Caffeine is a diuretic promoting increased urine flow, but this effect is small at the doses that have been shown to enhance
performance.57

Creatine
Overview

Creatine loading can acutely enhance the performance of sports involving repeated high-intensity exercise (eg, team sports), as well as the chronic
outcomes of training programmes based on these characteristics (eg, resistance or interval training), leading to greater gains in lean mass andmuscular strength and power.58 59

Mechanism

Supplementation increases muscle creatine stores, augmenting the rate of PCr resynthesis, thereby enhancing short-term, high-intensity exercise
capacity60 and the ability to perform repeated bouts of high-intensity effort.

Protocol of use

Loading phase: ~20 g/day (divided into four equal daily doses), for 5–7 days61
Maintenance phase: 3–5 g/day (single dose) for the duration of the supplementation period62
Note: concurrent consumption with a mixed protein/CHO source (~50 g of protein and CHO) may enhance muscle creatine uptake via insulin
stimulation.10

Performance Impact

Enhanced maximum isometric strength63 and the acute performance of single and repeated bouts of high-intensity exercise (<150 s duration); mostpronounced effects evident during tasks <30 s13 61
Chronic training adaptations include lean mass gains and improvements to muscular strength and power.58 59
Less common: enhanced endurance performance resulting from increased/improved protein synthesis, glycogen storage and thermoregulation64 65
Potential anti-inflammatory and antioxidant effects are noted.66

Further considerations andpotential side effects

No negative health effects are noted with long-term use (up to 4 years) when appropriate loading protocols are followed.67
A potential 1–2 kg BM increase after creatine loading (primarily as a result of water retention66 68) may be detrimental for endurance performanceor in events where the BM must be moved against gravity (eg, high jump, pole vault) or where athletes must achieve a specific BM target.

NitrateOverview

Dietary nitrate (NO3−) is a popular supplement that has been commonly investigated to assess any benefits for prolonged submaximal exercise69
and high-intensity, intermittent, short-duration efforts.70 71

Mechanism

Enhances nitric oxide (NO) bioavailability via the NO3−-nitrite-NO pathway, playing an important role in the modulation of skeletal muscle
function72
Nitrate augments exercise performance via an enhanced function of type II muscle fibres73; a reduced ATP cost of muscle force production; anincreased efficiency of mitochondrial respiration; an increased blood flow to the muscle; and a decrease in blood flow to VO2 heterogeneities.74

Protocol of use

High nitrate-containing foods include leafy green and root vegetables, including spinach, rocket salad, celery and beetroot.
Acute performance benefits are generally seen within 2–3 hours following an NO3− bolus of 5–9 mmol (310–560 mg).75
Prolonged periods of NO3− intake (>3 days) also appear beneficial to performance70 76 and may be a positive strategy for highly trained athletes,
where performance gains from NO3− supplementation appear harder to obtain.77

Performance impact

Supplementation has been associated with improvements of 4%–25% in exercise time to exhaustion and of 1%–3% in sport-specific TT
performances lasting <40 min in duration.73 78
Supplementation is proposed to enhance type II muscle fibre function,73 resulting in the improvement (3%–5%) of high-intensity, intermittent,
team-sport exercise of 12–40 min in duration.70 71
Evidence is equivocal for any benefit to exercise tasks lasting <12 min.76 79

Further considerations andpotential side effects

The available evidence suggests there appear to be few side effects or limitations to nitrate supplementation.
There may exist the potential for GI upset in susceptible athletes, and should therefore be thoroughly trialled in training.
There appears to be an upper limit to the benefits of consumption (ie, no greater benefit from 16.8 mmol (1041 mg) vs 8.4 mmol (521 mg)).80
Performance gains appear harder to obtain in highly trained athletes.77

Beta-alanine
Overview

Beta-alanine augments intracellular buffering capacity, having potential beneficial effects on sustained high-intensity exercise performance.

Mechanism

A rate-limiting precursor to the endogenous intracellular (muscle) buffer, carnosine; the immediate defence against proton accumulation in thecontracting musculature during exercise81
Chronic, daily supplementation of Beta-alanine increases skeletal muscle carnosine content.82

Protocol of use

Daily consumption of ~65 mg/kg BM, ingested via a split-dose regimen (ie, 0.8–1.6 g every 3–4 hours) over an extended supplement time frame of
10–12 weeks82
Continued444

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

Consensus statement
Table 3

Continued

Performance impact

Small, but potentially meaningful performance benefits (~0.2%–3%) during both continuous and intermittent exercise tasks of 30 s to 10 min induration82–84

Further considerations andpotential side effects

A positive correlation between the magnitude of muscle carnosine change and performance benefit remains to be established.82
Large interindividual variations in muscle carnosine synthesis have been reported.85
The supplement effectiveness appears harder to realise in well-trained athletes.86
There is a need for further investigation to establish the practical use in various sport-specific situations.82 87
Possible negative side effects include skin rashes and/or transient paraesthesia.

Sodium bicarbonate
Overview

Sodium bicarbonate augments extracellular buffering capacity, having potential beneficial effects on sustained high-intensity exercise performance.

Mechanism

Acts as an extracellular (blood) buffer, aiding intracellular pH regulation by raising the extracellular pH, and HCO3− concentrations81 88
The resultant pH gradient between the intracellular and extracellular environments leads to efflux of H+ and La− from the exercising muscle.88 89

Protocol of use

Single acute NaHCO3 dose of 0.2–0.4 g/kg BM, consumed 60–150 min prior to exercise90 91
Alternative strategies include the following:
Split doses (ie, several smaller doses giving the same total intake) taken over a time period of 30–180 min92
Serial loading with 3–4 smaller doses per day for 2–4 consecutive days prior to an event93–95

Performance impact

Enhanced performance (~2%) of short-term, high-intensity sprints lasting ~60 s in duration, with a reduced efficacy as the effort duration exceeds
10 min90

Further considerations andpotential side effects

Well-established GI distress may be associated with this supplement.
Strategies to minimise GI upset include the following:
Coingestion with a small, carbohydrate-rich meal (~1.5 g/kg BM carbohydrates)96
Use of sodium citrate as an alternative97
Split dose or stacking strategies93–95
Given the high potential for GI distress, thorough investigation into the best individualised strategy is recommended prior to use in a competition
setting.

Adverse effects

Adverse effects from the use of supplements may arise from anumber of factors, including the safety and composition of the
product per se and inappropriate patterns of use by athletes.
Poor practices by athletes include the indiscriminate mixing andmatching of many products without regard to total doses of some
ingredients or problematic interactions between ingredients.
Even commonly used products may have negative side effects,
especially when used outside the optimal protocol. For example,
iron supplementation in those with already adequate iron storescan result in symptoms that may begin with vomiting, diarrhoea
and abdominal pain, and develop to haemochromatosis andliver failure.26 Bicarbonate may cause gastrointestinal distresswhen ingested in amounts sufficient to enhance performance;
this can impair rather than improve performance and may counteract the benefits of other supplements taken at the same time.27
The ‘more is better’ philosophy, when applied to caffeine, may
result in side effects, including nausea, anxiety, accelerated
heart rate and insomnia, that outweigh the performance benefits.28 Unwanted outcomes become more common with caffeine
doses ≥9 mg/kg body mass, but maximal benefits are usuallyachieved with intakes of 3–6 mg/kg.29 The possibility of more
serious outcomes is illustrated by adverse, and potentially fatal,
responses in two separate incidents in which very large doses(up to 30 g) of caffeine were administered to healthy volunteers
participating in laboratory studies (http://www.​telegraph.​co.​uk/​
news/​2017/​01/​25/​university-​fined-​400k-​students-​taking-​part-​
caffeine-​experiment/). These incidents were due to errors in
the dose calculation: if this can happen in a university research
environment with supposed oversight by experienced staff, thepotential clearly exists for similar errors by athletes and coaches.
Athletes and members of their support team should be awareof the regulations that govern the manufacture and marketingof supplements. According to the 1994 DSHEA (https://​ods.​od.​
nih.​gov/​About/​DSHEA_​Wording.​aspx) passed by US Congress,
nutritional supplements sold in the USA that do not claim to
diagnose, prevent or cure disease are not subject to regulation by
the Food and Drugs Administration (FDA). Similar regulations

apply in most other countries, where supplements are regulated in the same way as food ingredients and are therefore
not subject to the stringent regulations that are applied to thepharmaceutical industry. This means that there is no requirement to prove claimed benefits, no requirement to show safetywith acute or chronic administration, no quality assurance ofcontent, and liberal labelling requirements. It is well-recognisedthat there are problems with some of the dietary supplements onsale, but the options open to those responsible for food safety
are limited by the legislation that applies. The FDA regularly
uses its powers to recall products in breach of the regulations,although they fully admit that their resources are insufficientfor comprehensive monitoring, and recalls generally occur only
after many people are harmed (ht​tps:​//ww​w.fd​a.go​v/food/​recallsoutbreaksemergencie​s/​r​ecal​ls/​d​efault.​htm): they have recently
recalled supplement products containing excessive doses of vitamins A, D, B6 and selenium because of potentially toxic levelsof these components. Examples of product complaints haveincluded the presence of impurities, including lead, broken glassand metal fragments, because of the failure of the producers to
observe good manufacturing practice. The risk of gastrointestinal upset because of poor hygiene during the production andstorage of products is also of concern. Although this may seema minor inconvenience, and of similarity to food safety issues,
the coincidence of problems around a crucial training period orcompetitive event may significantly interfere with the athlete’s
performance goals. It should be noted, though, that all of these
problems are also regularly reported in normal foods.
Some supplements may actually cause harm to health, butthese can be difficult to identify, and products are usually withdrawn only after a significant number of adverse events haveoccurred. For example, a range of products containing hydroxycitric acid were withdrawn from sale, but only after they werelinked with the death of one consumer and with a substantial
number of other cases of liver toxicity, cardiovascular problems
and seizures (https://www.​fda.​gov/​downloads/​safety/​recalls/​
enforcementreports/​ucm169089.​pdf). The extent of the problem
is illustrated by the fact that, in the USA in 2015, approximately

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

445

Consensus statement
Table 4

Nutritional supplements for immune health in athletes: proposed mechanism of action and evidence for efficacy

Supplement

Proposed mechanism of action

Evidence for efficacy

Vitamin D

This is an essential fat-soluble vitamin known to influence
several aspects of immunity, particularly innate immunity(eg, expression of antimicrobial proteins). Skin exposure to
sunlight accounts for 90% of the source of vitamin D.

Moderate support
Evidence for deficiency in some athletes and soldiers, particularly in the winter (decreased
skin sunlight exposure)
Deficiency has been associated with increased URS.
Recommend 1000 IU/day D3 autumn-spring to maintain sufficiency
Further support required98

Probiotics

Probiotics are live micro-organisms that when administered Moderate support in athletes with daily dose of ~1010 live bacteria
orally for several weeks can increase the numbers of
Cochrane review of 12 studies (n=3720) shows ~50% decrease in URS incidence and ~2 day
beneficial bacteria in the gut. These have been associated shortening of URS; minor side effects.
with a range of potential benefits to gut health, as well as More evidence is required supporting efficacy to reduce gastrointestinal distress andmodulation of immune function.
infection, for example, in a travelling athlete.23 99

Vitamin C

This is an essential water-soluble antioxidant vitaminthat quenches ROS and augments immunity. It reduces
interleukin-6 and cortisol responses to exercise in humans.

Moderate support for ‘preventing URS’
Cochrane review of 5 studies in heavy exercisers (n=598) shows ~50% decrease in URS
taking vitamin C (0.25–1.0 g/day).
Further support required
Unclear if antioxidants blunt adaptation in well-trained
Relatively small effects on cortisol compared with carbohydrate; immune measures nodifferent from placebo
No support for ‘treating URS’
Cochrane reviews show no benefit of initiating vitamin C supplementation (>200 mg/day)after onset of URS.100 101

Carbohydrate (drinks,
gels)

It maintains blood glucose during exercise, lowers stresshormones, and thus counters immune dysfunction.

Low-moderate support
Ingestion of carbohydrate (30–60 g/hour) attenuates stress hormone and some, but not all,immune perturbations during exercise.
Very limited evidence that this modifies infection risk in athletes19 102

Bovine colostrum

First milk of the cow that contains antibodies, growth
factors and cytokines
Claimed to improve mucosal immunity and increase
resistance to infection

Low-moderate support that bovine colostrum blunts the decrease in saliva antimicrobial
proteins after heavy exercise
Some evidence in small numbers of participants that bovine colostrum decreases URS
Further support required103 104

Polyphenols, forexample, Quercetin

These are plant flavonoids. In vitro studies show strong
anti-inflammatory, antioxidant and antipathogenic
effects. Animal data indicate an increase in mitochondrial
biogenesis and endurance performance.

Low-moderate support
Human studies show some reduction in URS during short periods of intensified training andmild stimulation of mitochondrial biogenesis and endurance performance, although in small
numbers of untrained subjects.
Limited influence on markers of immunity
Putative antiviral effect for Quercetin
Further support required105 106

Zinc

This is an essential mineral that is claimed to reduceincidence and duration of colds. Zinc is required for DNA
synthesis and as an enzyme cofactor for immune cells.
Zinc deficiency results in impaired immunity (eg, lymphoid
atrophy) and zinc deficiency is not uncommon in athletes.

No support for ‘preventing URS’
High doses of zinc can decrease immune function and should be avoided.
Moderate support for ‘treating URS’
Cochrane review shows benefit of zinc acetate lozenges (75 mg) to decrease duration of
URS; however, zinc must be taken <24 hours after onset of URS for duration of cold only.
Side effects include bad taste and nausea.24

Glutamine

This is a non-essential amino acid that is an important
Limited support
energy substrate for immune cells, particularly lymphocytes. Supplementation before and after exercise does not alter immune perturbations.
Circulating glutamine is lowered after prolonged exercise
Some evidence of a reduction in URS after endurance events in competitors receiving
and very heavy training.
glutamine supplementation (2×5 g)
Mechanism for therapeutic effect requires investigation.107 108

Caffeine

This is a stimulant found in a variety of foods and drinks(eg, coffee and sports drinks). Caffeine is an adenosine
receptor antagonist and immune cells express adenosine
receptors.

Limited support
Evidence that caffeine supplementation activates lymphocytes and attenuates the fall inneutrophil function after exercise
Efficacy for altering URS in athletes remains unknown.109 110

Echinacea

This is a herbal extract claimed to enhance immunity via
stimulatory effects on macrophages. There is some in vitro
evidence for this.

Limited support
Early human studies indicated possible beneficial effects, but more recent, larger scale
and better controlled studies indicate no effect of Echinacea on infection incidence or cold
symptom severity.111 112

Omega-3 PUFAs

Found in fish oil
Limited support for blunting inflammation and functional changes after muscle-damaging
May influence immune function by acting as a fuel, in their eccentric exercise in humans and no evidence of reducing URS in athletes113 114
role as membrane constituents or by regulating eicosanoid
formation, for example, prostaglandin
Prostaglandin is immunosuppressive.
Claimed to exert anti-inflammatory effects postexercise

Vitamin E

An essential fat-soluble antioxidant vitamin that quenches
exercise-induced ROS and augments immunity

No support
Immune-enhancing effects in the frail elderly but no benefit in young, healthy humans
One study actually showed that vitamin E supplementation increased URS in those underheavy exertion.
High doses may be pro-oxidative.115 116
Continued

446

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

Consensus statement
Table 4

Continued

Supplement

Proposed mechanism of action

Evidence for efficacy

β-glucans

Polysaccharides derived from the cell walls of yeast, fungi,
algae and oats that stimulate innate immunity

No support in humans
Effective in mice inoculated with influenza virus; however, human studies with athletes
show no benefits.117 118

PUFA, polyunsaturated fatty acids; ROS, reactive oxygen species; URS, upper respiratory symptoms.

23 000 emergency department visits annually are reported to
be associated with dietary supplement use.30 This figure can beviewed as substantial, or it can be seen as small compared withthe total number of adverse responses associated with the useof medications.15 However, minor problems that do not require
acute medical aid may still be sufficient to interrupt training or
prevent participation, so this statistic probably underestimates
the risk for athletes.
The biggest concern for athletes who compete under an antidoping code (usually the World Anti-Doping Code, as publishedby WADA) is that supplements can contain prohibited substancesthat result in an antidoping rule violation (ADRV). Athletes—
and their support teams—may be at risk for an ADRV if thereis evidence that they have used or attempted to use products
containing ingredients on the Prohibited List (www.​wada.​ama.​org). A common problem is the recording of an adverse analytical finding (AAF) of a prohibited substance in a urine sample(‘positive drug test’) as a result of supplement use.31 Millions ofathletes may be subject to antidoping testing, although these aremostly professional-level, national-level or international-levelathletes. For these athletes in particular, even if the ingestion of
the prohibited substance was unintentional, the rules of strict
liability within the World Anti-Doping Code mean that an
AAF will be recorded, and may mean the loss of medals won
or records set, and financial sanctions as well as temporary or
permanent suspension from competition. It also damages theathlete’s reputation and may lead to loss of employment andincome through failed sponsorship opportunities. Where there
has been deliberate cheating or benefit accrued from the use of aprohibited substance, these penalties seem entirely appropriate,
but it is undoubtedly true that some ADRVs can be attributed
to the innocent ingestion of prohibited substances in dietary
supplements, with catastrophic results for the athlete.
One cause of an AAF arising from supplement use relates to an
athlete’s failure to read product labels to recognise the presenceof prohibited substances. Many athletes consider supplements
to be ‘natural’ or ‘regulated’ and therefore safe. Other athletes
are confused by the number of chemical names for some prohibited substances and thus fail to recognise them on the productlabel. However, the most worrying cause of an inadvertent AAF
is the use of supplements that contain prohibited substances as
an undeclared ingredient or contaminant. Since the publicationof the seminal study on the presence of undeclared prohibited
substances in supplements,32 there have been numerous reportsof supplement contamination.31 Recent reviews suggest that
this problem remains33 (http://www.​informed-​sport.​com/​news/​
australian-​supplements-​survey-​highlights-​need-​testing). It isdifficult to gain a perspective of the true prevalence of supplement
contamination. Although the original study reported that ~15%
of more than 600 products acquired from around the worldcontained undeclared prohormones,32 this and other investigations rarely include a truly random sample of the supplements
and sports foods used by athletes. Some individual products or
categories of products can be considered inherently more at riskof contamination due to the country of origin, the manufacturer,

the type of product and the range of declared ingredients(https://www.​usada.​org/​substances/​supplement-​411/).
Nevertheless, it should also be recognised that common supplements,
including vitamin C, multivitamins and minerals, have also beenfound, although rarely, to contain prohibited substances.34 The
range of prohibited substances found as undeclared ingredientsin supplements now includes products from many sections of
WADA's List of Prohibited Substances and Methods, including
stimulants, anabolic agents, selective androgen receptor modulators, diuretics, anorectics and β2 agonists.33
In some cases, the amount of the prohibited substance in a
supplement may be high, even higher than the normal therapeutic dose. For example, Geyer et al35 reported the analysisof metandienone (commonly known as methandrostenolone or
Dianabol) in high amounts in a ‘body building’ supplement fromEngland. The recommended amount of the supplement would
have supplied a dose of 10–43 mg; in comparison, the typicaltherapeutic dose of this drug was 2.5–5 mg/day,36 although its
medical use has been discontinued in most countries for many
years. This amount would certainly have a potent anabolic
effect, but would likely produce serious side effects, including
psychiatric and behavioural effects, and significant damage toa range of body systems including the liver.37 Unlike many ofthe earlier cases involving steroids related to nandrolone andtestosterone, this is not a trivial level of contamination and raises
the possibility of deliberate adulteration of the product with theintention of producing a measurable effect on muscle strengthand muscle mass. Most reports of adverse health outcomes
resulting from supplement use have focused on liver problemsof varying degrees of severity, but other organs are also affected.
One epidemiological case–control study38 examined the association between use of muscle-building supplements and testicular germ cell cancer (TGCC) risk, with 356 TGCC cases and513 controls from eastern USA. The OR for the use of musclebuilding supplements in relation to risk of TGCC was elevated(OR=1.65, 95% CI 1.11 to 2.46), with significantly stronger
associations for early users and longer periods of use.
Ironically, supplements that are contaminated with extremely
small amounts of prohibited substances—too low to have any
physiological effect—may still cause a positive doping outcome.
For instance, ingestion of 19-norandrostenedione, a precursorof nandrolone, will result in the appearance in the urine of
19-norandrosterone, the diagnostic metabolite for nandrolone.
If the urinary concentration of 19-norandrosterone exceeds
2 ng/mL, an AAF is recorded.39 The addition of as little as
2.5 µg of 19-norandrostenedione to a supplement can result ina urinary concentration of 19-norandrosterone that exceeds thisthreshold.40 These amounts are close to the limits of detectionof the analytical methods currently applied to the analysis of
dietary supplements, and are far below the levels of contamination deemed acceptable from a health and safety perspective.
Various efforts are being made to address the problems,
including the use of third-party auditing activities to identify products that athletes may consider to be at ‘low risk’ ofcontaining prohibited substances. There can be no absolute

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

447

Consensus statement
Table 5

Supplements that may assist with training capacity, recovery, muscle soreness and injury management
Evidence for efficacy41

Supplement

Proposed mechanism of action

Creatine monohydrate
Creatine is a naturally occurring nutrient,consumed in the diet and synthesised in
the body. Recommended supplement doseis 20 g/day for 5 days, followed by 3–5 g/
day to increase and maintain elevated body
creatine levels.119 120

Enhanced adaptive response to exercise via increased
Many studies demonstrate improved training adaptations, such as
growth factor/gene expression and increased intracellular increased lean mass or strength, indicating an enhanced adaptive
water
response to exercise.12 13 121
Reduced symptoms of, or enhanced recovery from, muscle damaging
Reduced symptoms of, or enhanced recovery from,exercise (eg, DOMS) have been reported in some, but not all studies
muscle damaging exercise (eg, DOMS)(reviewed in ref 122).
Enhanced recovery from disuse or immobilisation/
Enhanced recovery from disuse or immobilisation/extreme inactivity has
extreme inactivity
been reported in some, but not all studies (reviewed in ref 12).
Improved cognitive processing
Improved cognitive processing is reported in most studies, especially
Decreased risk/enhanced recovery from mTBI
when volunteers were fatigued by sleep deprivation or mental/physicaltasks (reviewed in refs 11 123–125). The effects in athletes have not beenwell-characterised, and only one group attempted to translate theseeffects to athletic performance, although with a positive result.126
Decreased damage and enhanced recovery from mTBI are supported byopen-label trials in children127 128 and using animal models.129 These data
are not conclusive and more research is warranted. However, athletes
at risk for concussion, who already ingest creatine supplements for
performance or muscular benefits, may receive important brain benefits
as well.
A small increase in body mass is common with supplementation. Thismay be relevant for sports with weight classes/restrictions or where
increased body mass may decrease performance.

Beneficial effects of HMB on strength and fat-free mass are small, while
Beta-hydroxy beta-methylbutyrate (HMB)
Enhanced adaptive response to exercise via
the effects on muscle damage are unclear.131
HMB is a metabolite of the amino aciddecreased protein breakdown, increased protein
Recent reports of ‘steroid like’ gains in strength, power and fatleucine. Manufacturer-recommended dosage synthesis, increased cholesterol synthesis, increased
is 3 g/day.
growth hormone and IGF-I mRNA, increased proliferation free mass, and reductions in muscle damage from HMB-freeacid supplementation,132–134 have not been reproduced and seemand differentiation of satellite cells and inhibited
unlikely.135
apoptosis (reviewed in ref 130)
Potential use for HMB during extreme inactivity/disuse or recovery
from injury, but these effects have only been described in older adults
following 10 days of bed rest.136
Benefits of HMB supplementation could most likely be obtained fromnormal dietary protein or whole protein supplements,137 so HMB
supplements may not be more effective than adhering to the current
protein intake recommendations.
Omega-3 fatty acids
About 2 g/day

Improved cognitive processing
Decreased risk/enhanced recovery from mTBI
Increased muscle protein synthesis
Reduced symptoms of, or enhanced recovery from,muscle damaging exercise (eg, DOMS)

Improved cognitive processing following omega-3 fatty acidsupplementation shown in healthy older adult with mild or severe
cognitive impairment (reviewed in ref 138). It is not known if thesebenefits would occur in young, healthy athletes, or how this would
translate to athletic performance.
Animal data show that the structural damage and cognitive decline
associated with mTBI are reduced/attenuated with omega-3 fatty
acid supplementation when ingested either before or after the injury(reviewed in refs 138–140). Two case studies support these findings,141 142
and large, double-blind, placebo-controlled trials are currently under way(ClinicalTrials.gov NCT101903525 and NCT01814527).
In muscle, omega-3 fatty acid supplementation can increase muscle
protein synthesis,143 144 but this may not occur when protein is ingested
after exercise in recommended amounts.143 144
Anti-inflammatory effects of omega-3 fatty acid intake may reducemuscle damage or enhance recovery from intense, eccentric exercise (eg,decrease DOMS), but this is not a consistent finding.145 146
No indication that decreased omega-3 fatty acids in the body impair
performance, and high-dose supplements can cause some adverse effects(reviewed in refs 114 139), so the best recommendation may be to include
rich sources of omega-3 fatty acids, such as fatty fish, in the diet insteadof supplements. Low risk but unclear if supplementation should be
pursued by athletes, in lieu of including fatty fish in the diet as a sourceof omega-3 fatty acids.
Fish oil or omega-3 fatty acid supplement consumption could include
heavy metal contaminants, or cause bleeding, digestive problems and/or increased LDL.
Continued

448

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

Consensus statement
Table 5

Continued

Supplement

Evidence for efficacy41

Proposed mechanism of action

Vitamin D
Enhanced adaptive response to exercise
An essential fat-soluble vitamin
Decreased stress fractures
Skin exposure to sunlight normally accounts
for 90% of the source of vitamin D.

Gelatin and vitamin C/collagen
Recommended dose is 5–15 g gelatin with50 mg vitamin C.153
Collagen hydrolysate dose is about 10 g/day.154 155

Data on the effects of vitamin D supplementation on muscle function andrecovery are equivocal, with discrepancies likely explained by differences
in baseline vitamin D concentrations prior to supplementation.147–150
Collectively, these data strongly suggest a role for adequate vitamin D in
the adaptive process to stressful exercise.
Low vitamin D status is associated with a 3.6× higher stress fracturerisk in Finnish military recruits.151 US Naval recruits supplemented with
800 IU/day of vitamin D3 and 2000 mg calcium reduced stress fracture
incidence by 20%.152 More data are needed, but it appears that vitaminD status relates to stress fracture risk, and supplementation, when
warranted, may reduce this risk.

Increased collagen production
Thickened cartilage
Decreased joint pain

Gelatin and collagen supplements appear to be low risk.
Few data available,153–155 but increased collagen production anddecreased pain seem possible.
Functional benefits, recovery from injury, and effects in elite athletes are
not known.

Anti-inflammatory supplements
Anti-inflammatory effects
Curcumin (a constituent of the spice
Reduced symptoms of, or enhanced recovery, fromturmeric) is often ingested for antimuscle damaging exercise (eg, DOMS)
inflammatory effects at a dose of about
5 g/day.
Tart cherry juice at a dose of about 250–
350 mL (30 mL if concentrate) twice daily for
4–5 days before an athletic event or for 2–3
days afterwards to promote recovery

Decreases in inflammatory cytokines and/or indirect markers of muscle
damage with anti-inflammatory supplements such as curcumin156–158 andtart cherry juice (reviewed in refs 159 160) have been reported.
Anti-inflammatory effects may be beneficial, although benefits may besport/training-specific. More research is needed before these compounds
can be recommended to athletes.

DOMS, delayed-onset muscle soreness; mTBI, mild traumatic brain injury (concussion).

guarantee that any product is entirely safe, but these schemes
do help the athlete to manage the risk. Athletes contemplating
the use of dietary supplements should consider very carefully

Table 6

whether the possible benefits outweigh the risks of a doping
offence that might end their career.

Supplements promoted to assist with physique changes: gain in lean mass and loss of body fat mass
Proposed mechanism of action

Evidence for efficacy25

Protein
Usually comprised isolated proteins from various
sources (whey and soy most common)
Recommended daily dose: 1.6 g protein/kg/day
optimal (up to 2.2 g/kg/day with no adverse effects)
Recommended per-meal doses: 0.3–0.5 g protein/kg(3–4 times per day and in close temporal proximity to
exercise, with postexercise being consistently shown
to be effective)

Enhances lean mass gains when ingested during
programmes of resistance training due to increased
provision of building blocks (amino acids) and leucine
as a trigger for a rise in muscle protein synthesis andsuppression of muscle protein breakdown

Meta-analyses focusing on younger and older participants
have shown positive effects enhancing gains in muscle
mass,161 162 but effects are not large.

LeucineStimulates muscle protein synthesis and suppresses protein Short-term mechanistic data available,137 but no long-term
breakdown (possibly through insulin)
trials showing efficacy163

Supplement
Gaining LBM*

Losing fat mass†Protein
From increased dietary sources or supplemental
isolated proteins

Enhances fat mass loss and promotes retention of lean
mass

Meta-analyses confirm small but significant effects of greater
dietary protein in weight loss to enhance fat mass loss andpromote lean mass retention.164 165

Pyruvate

No data

Small to trivial effect166

Chromium

Potentiates biological actions of insulin

No effect167

Green tea (polyphenol catechins and caffeine)

Thermogenic agent and/or lipolytic enhancing agent

Small to trivial effect168

α-Lipoic acid

No clear role, but possible antioxidant

Small to trivial effect169

Conjugated linolenic acid

Changes membrane fluidity favouring enhanced fat
oxidation

Small to trivial effect170

Konjac fibre (glucomannan)

Water-soluble polysaccharide—dietary fibre

Small to trivial effect171

Omega-3 polyunsaturated fatty acids

No clear role, but possible appetite suppression, improved
blood flow and/or modulator of gene expression

Small to trivial effect172

ChitosanLipid-binding agent to reduce lipid absorption

Small to trivial effect173*In combination with a progressive resistance exercise programmes.
†In combination with an exercise-induced and/or diet-induced energy deficit.

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

449

Consensus statement

Figure 2 Flow chart to guide informed decision making and reducing risk of antidoping rule violation during nutritional supplement use. MD,
medical doctors.

Practical implications and decision tree

Dietary supplements are an established part of the landscapeof modern sport and are likely to remain so. Athletes who takesupplements often have no clear understanding of the potential effects of supplements they are using, but supplements
should be used only after a careful cost-benefit analysis has been
conducted. On one side of the decision tree are the rewards,
the most obvious of which are correction of nutrient deficiencies, achievement of nutritional goals, or enhancement of one or
another physiological/biochemical function to directly or indirectly improve performance. On the other side lie the costs, thepossibility of using an ineffective supplement, the possible risks
to health and the potential for an ADRV. A flow of questions
that could be posed in reaching an informed decision is shownin figures 2 and 3.
In deciding whether to use a supplement, athletes should
consider all aspects of their maturation in, and preparation
450

for, their event to ensure that the supplement under consideration provides an advantage that no other strategy can address.
Whether the supplement is practical to use should also beassessed: is the product available, affordable, tolerated andcompatible with the athlete’s other goals? The input of theathlete’s coaching team and medical/science support network
is important. Athletes who do not have regular access to sucha network should consider decisions around supplement use as
an important reason to consult an independent sports nutrition
expert as well as a physician. Analysis of the evidence around theeffectiveness of supplements and their safety is often difficult.
A complete nutritional assessment may provide an appropriate
justification for the specific use of nutritional supplements andsports foods. For a small number of sports supplements, thereis good evidence of a performance effect or indirect benefit forsome athletes in some specific situations with little or no risk ofadverse outcomes.28 41 Professional advice is often important in

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

Consensus statement

Figure 3

Flow chart to guide informed decision making and reducing risk of antidoping rule violation during ergogenic supplement use.

ensuring that the athlete is sufficiently knowledgeable about theappropriate protocol for use of these supplements, but individual
athletes may respond very differently to a given supplement, withsome exhibiting a markedly beneficial effect while others experiencing no benefit or even a negative effect on performance.
Furthermore, the situation in which the athlete wishes to use thesupplement may differ in important ways from its substantiateduse. Repeated trials may be necessary to establish whether a true
effect, rather than just random variation, is seen in response touse of any novel intervention. Some trial and error may also be
involved in fine-tuning the supplement protocol to suit the needsof the specific situation of use or the individual athlete.
Evidence to support the effectiveness and safety of manyof the supplements targeted at athletes, however, is largely
absent. There seems to be little incentive for those selling
supplements to invest the substantial sums needed to undertake detailed scientific evaluation of their products. Even
where some evidence does exist, it may not be relevant to thehigh-performance athlete because of limitations in the study
design (such as the specificity of the exercise tests), the study
population or the context of use. Failure to verify the composition of the supplements used may also give misleading results.
It seems sensible to exercise caution when using supplements,
as any compound that has the potential to enhance health or

exercise performance by altering physiological function mustalso have the potential for adverse effects in some individuals.
Athletes should see good evidence of a performance or otherbenefit, and should be confident that it will not be harmful tohealth, before accepting the financial cost and the health or
performance risks associated with any supplement. Finally, theathlete should be sure, if supplements or sports foods are to be
used, that they have undertaken due diligence to source products that are at low risk of containing prohibited substances.

Conclusion

Dietary supplements can play a small role in an athlete’s
sports nutrition plan, with products that include essential
micronutrients, sports foods, performance supplements andhealth supplements all potentially providing benefits. Some
supplements, when used appropriately, may help athletes tomeet sports nutrition goals, train hard, and stay healthy andinjury-free. A few supplements can directly enhance competition performance. However, it takes considerable effort andexpert knowledge to identify which products are appropriate,
how to integrate them into the athlete’s sports nutrition plan,and how to ensure that any benefits outweigh the possible
negative side effects, including the potential for an ADRV. A

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

451

Consensus statement
strict risk-benefit analysis involving a decision tree approachto the effectiveness, safety and risks should identify the small
number of products that may benefit the athlete. Such ananalysis requires the input of a well-informed sports nutrition
professional.
Author affiliations
1
School of Medicine, St Andrews University, St Andrews, UK
2
Sports Nutrition, Australian Institute of Sport, Canberra, Australia
3
Mary MacKillop Institute for Health Research, Melbourne, Australia
4
Department of Neurology, Schulthess Clinic, Zurich, Switzerland
5
Department of Family & Consumer Sciences (Human Nutrition), University of
Wyoming, Laramie, Wyoming, USA
6
School of Human Sciences (Exercise and Sport Science), The University of Western
Australia, Crawley, Western Australia, Australia
7
Western Australian Institute of Sport, Mount Claremont, Australia
8
Department of Kinesiology, McMaster University, Hamilton, Canada
9Department of Health, Nutrition, and Exercise Science, Messiah College,
Mechanicsburg, Pennsylvania, USA
10
College of Health and Behavioural Sciences, Bangor University, Bangor, UK
11
The Norwegian Olympic and Paralympic Committee and Confederation of Sport,
Oslo, Norway
12
Institute of Biochemistry, Center for Preventive Doping Research, German Sport
University, Cologne, Germany
13
Human Physiology Research Group, Vrije Universiteit Brussel, Brussel, Belgium
14Department of Human Biology and Movement Sciences, NUTRIM School of
Nutrition and Translational Research in Metabolism, Maastricht University Medical
Centre, Maastricht, The Netherlands
15
Human Health & Nutritional Sciences, University of Guelph, Ontario, Canada
16
BMJ, London, UK
17
Department of Science and Medicine, World Anti-Doping Agency (WADA),Montreal, Canada
18
English Institute of Sport, Loughborough, UK
19
Medical and Scientific Commission, International Olympic Committee, Lausanne,
Switzerland
20
Medical and Scientific Department, International Olympic Committee, Lausanne,
Switzerland
21
Anti-Doping Foundation, Stockholm, Sweden
22
Human Health and Nutritional Sciences, Health and Performance, Centre Universityof Guelph, Guelph, Ontario, Canada
23
Medical and Scientific Commission Games Group, International Olympic
Committee, Lausanne, Switzerland
Funding This research received no specific grant from any funding agency in the
public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Open Access This is an Open Access article distributed in accordance with theCreative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which
permits others to distribute, remix, adapt, build upon this work non-commercially,and license their derivative works on different terms, provided the original work
is properly cited and the use is non-commercial. See: http://​creativecommons.​org/​
licenses/​by-​nc/​4.​0/© Article author(s) (or their employer(s) unless otherwise stated in the text of thearticle) 2018. All rights reserved. No commercial use is permitted unless otherwise
expressly granted.

References

1 Bailey RL, Gahche JJ, Lentino CV, et al. Dietary supplement use in the United States,
2003-2006. J Nutr 2011;141:261–6.
2 Fennell D. Determinants of supplement usage. Prev Med 2004;39:932–9.
3 Supplements UNood. Dietary supplement health and education act of 1994. 1994.
https://​ods.​od.​nih.​gov/​About/​DSHEA_​Wording.​aspx#​sec31994 (accessed 22 Nov
2017).
4 Maughan RJ, Depiesse F, Geyer H. International Association of Athletics
Federations. The use of dietary supplements by athletes. J Sports Sci
2007;25(Suppl 1):S103–13.
5 Garthe I, Maughan MRJ. Athletes and Supplements - prevalance and perspectives.
Int J Sport Nutr Exerc Metab. In Press. 2018.
6 Prasad AS. Zinc is an Antioxidant and Anti-Inflammatory Agent: Its Role in Human
Health. Front Nutr 2014;1:14.
7 Solomons NW. Mild human zinc deficiency produces an imbalance between cellmediated and humoral immunity. Nutr Rev 1998;56():27–8.

452

8 Stellingwerff T, Cox GR. Systematic review: Carbohydrate supplementation on
exercise performance or capacity of varying durations. Appl Physiol Nutr Metab
2014;39:998–1011.
9 Peake JM, Neubauer O, Walsh NP, et al. Recovery of the immune system after
exercise. J Appl Physiol 2017;122:1077–87.
10 Steenge GR, Simpson EJ, Greenhaff PL. Protein- and carbohydrate-induced
augmentation of whole body creatine retention in humans. J Appl Physiol
2000;89:1165–71.
11 Gualano B, Roschel H, Lancha AH, et al. In sickness and in health: the widespread
application of creatine supplementation. Amino Acids 2012;43:519–29.
12 Heaton LE, Davis JK, Rawson ES, et al. Selected in-season nutritional strategies
to enhance recovery for team sport athletes: a practical overview. Sports Med
2017;47:2201–18.
13 Branch JD. Effect of creatine supplementation on body composition andperformance: a meta-analysis. Int J Sport Nutr Exerc Metab 2003;13:198–226.
14 Burke LM, Peeling P. Methodologies for investigating performance changes
with supplement use. Int J Sport Nutr Exerc Metab 2018. doi: 10.1123/
ijsnem.2017-0325. [Epub ahead of print].
15 Maughan RJ, Shirreffs SM, Vernec A. Making decisions about supplement use. Int J
Sport Nutr Exerc Metab. In Press. 2018.
16 Clark A, Mach N. The Crosstalk between the gut microbiota and mitochondria during
Exercise. Front Physiol 2017;8:319.
17 Ribeiro IF, Miranda-Vilela AL, Klautau-Guimarães MN, et al. The influence oferythropoietin (EPO T → G) and α-actinin-3 (ACTN3 R577X) polymorphisms
on runners’ responses to the dietary ingestion of antioxidant supplementation
based on pequi oil (Caryocar brasiliense Camb): a before-after study. J Nutrigenet
Nutrigenomics 2013;6:283–304.
18 Larson-Meyer DE, Woolf K, Burke LM. Assessment of nutrient status in athletes andthe need for supplementation. Int J Sport Nutr Exerc Metab 2018. doi: 10.1123/
ijsnem.2017-0338. [Epub ahead of print].
19 Bermon S, Castell LM, Calder PC, et al. Consensus Statement Immunonutrition andExercise. Exerc Immunol Rev 2017;23:8–50.
20 Nikolaidis MG, Kerksick CM, Lamprecht M, et al. Does Vitamin C and E
supplementation impair the favorable adaptations of regular exercise? Oxid Med
Cell Longev 2012;2012:1–11.
21 Paulsen G, Cumming KT, Holden G, et al. Vitamin C and E supplementation hampers
cellular adaptation to endurance training in humans: a double-blind, randomised,
controlled trial. J Physiol 2014;592:1887–901.
22 Powers S, Nelson WB, Larson-Meyer E. Antioxidant and Vitamin D supplements forathletes: sense or nonsense? J Sports Sci 2011;29(Suppl 1):S47–S55.
23 Hao Q, Dong BR, Wu T. Probiotics for preventing acute upper respiratory tract
infections. Cochrane Database Syst Rev 2015;2:CD006895.
24 Singh M, Das RR. Zinc for the common cold. Cochrane Database Syst Rev
2013;6:CD001364.
25 Hector AJ, Phillips SM. Protein recommendations for weight loss in elite athletes: afocus on body composition and performance. Int J Sport Nutr Exerc Metab 2018. doi:
10.1123/ijsnem.2017-0273. [Epub ahead of print].
26 Mettler S, Zimmermann MB. Iron excess in recreational marathon runners. Eur J Clin
Nutr 2010;64:490–4.
27 Carr AJ, Gore CJ, Dawson B. Induced alkalosis and caffeine supplementation: effects
on 2,000-m rowing performance. Int J Sport Nutr Exerc Metab 2011;21:357–64.
28 Peeling P, Binnie MJ, Goods PSR, et al. Evidence-based supplements for theenhancement of athletic performance. Int J Sport Nutr Exerc Metab 2018. doi:
10.1123/ijsnem.2017-0343. [Epub ahead of print].
29 Burke LM. Caffeine and sports performance. Appl Physiol Nutr Metab
2008;33:1319–34.
30 Geller AI, Shehab N, Weidle NJ, et al. Emergency department visits for adverse events
related to dietary supplements. N Engl J Med 2015;373:1531–40.
31 Maughan RJ. Contamination of dietary supplements and positive drug tests in sport.
J Sports Sci 2005;23:883–9.
32 Geyer H, Parr MK, Mareck U, et al. Analysis of non-hormonal nutritional supplements
for anabolic-androgenic steroids - results of an international study. Int J Sports Med
2004;25:124–9.
33 Martínez-Sanz JM, Sospedra I, Ortiz CM, et al. Intended or unintended doping? A
review of the presence of doping substances in dietary supplements used in sports.
Nutrients 2017;9:1093.
34 Geyer H, Parr MK, Koehler K, et al. Nutritional supplements cross-contaminated andfaked with doping substances. J Mass Spectrom 2008;43:892–902.
35 Geyer H, Bredehoft M, Marek U, et al. Hohe Dosen des Anabolikums Metandienon in
Nahrungserganzungsmitteln. Deutsche Apotheke Zeit 2002;142:29.
36 Goodman LS, Gilman A. Pharmacological basis of therapeutics. 5th edn: Macmillan
Publishing Co, 1975:1462.
37 Solimini R, Rotolo MC, Mastrobattista L, et al. Hepatotoxicity associated with
illicit use of anabolic androgenic steroids in doping. Eur Rev Med Pharmacol Sci
2017;21:7–16.
38 Li N, Hauser R, Holford T, et al. Muscle-building supplement use and increased risk oftesticular germ cell cancer in men from Connecticut and Massachusetts. Br J Cancer
2015;112:1247–50.

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

Consensus statement
39 Baume N, Avois L, Schweizer C, et al. [13C]Nandrolone excretion in trained athletes:interindividual variability in metabolism. Clin Chem 2004;50:355–64.
40 Watson P, Judkins C, Houghton E, et al. Urinary nandrolone metabolite detection
after ingestion of a nandrolone precursor. Med Sci Sports Exerc 2009;41:766–72.
41 Rawson ES, Miles MP, Larson-Meyer DE. Dietary supplements for health, adaptation,and recovery in athletes. Int J Sport Nutr Exerc Metab 2018. doi: 10.1123/
ijsnem.2017-0340. [Epub ahead of print].
42 Hossein-nezhad A, Holick MF. Vitamin D for health: a global perspective. Mayo Clin
Proc 2013;88:720–55.
43 Larson-Meyer DE, Willis KS. Vitamin D and athletes. Curr Sports Med Rep
2010;9:220–6.
44 Heaney RP. Vitamin D: criteria for safety and efficacy. Nutr Rev 2008;66:S178–S181.
45 Thomas DT, Erdman KA, Burke LM. American college of sports medicine joint
position statement. Nutrition and athletic performance. Med Sci Sports Exerc
2016;48:543–68.
46 Gibson RS. Principles of nutritional assessment. Second Edn. New York, NY: Oxford
University Press, 2005.
47 Moretti D, Goede JS, Zeder C, et al. Oral iron supplements increase hepcidin anddecrease iron absorption from daily or twice-daily doses in iron-depleted young
women. Blood 2015;126:1981–9.
48 Spriet LL. Exercise and sport performance with low doses of caffeine. Sports Med
2014;44 (Suppl 2):175–84.
49 Ganio MS, Klau JF, Casa DJ, et al. Effect of caffeine on sport-specific endurance
performance: a systematic review. J Strength Cond Res 2009;23:315–24.
50 French C, McNaughton L, Davies P, et al. Caffeine ingestion during exercise
to exhaustion in elite distance runners. Revision. J Sports Med Phys Fitness
1991;31:425–32.
51 Paton C, Costa V, Guglielmo L. Effects of caffeine chewing gum on race
performance and physiology in male and female cyclists. J Sports Sci
2015;33:1076–83.
52 Talanian JL, Spriet LL. Low and moderate doses of caffeine late in exercise improve
performance in trained cyclists. Appl Physiol Nutr Metab 2016;41:850–5.
53 Wiles JD, Coleman D, Tegerdine M, et al. The effects of caffeine ingestion on
performance time, speed and power during a laboratory-based 1 km cycling timetrial. J Sports Sci 2006;24:1165–71.
54 Schneiker KT, Bishop D, Dawson B, et al. Effects of caffeine on prolonged
intermittent-sprint ability in team-sport athletes. Med Sci Sports Exerc
2006;38:578–85.
55 Wellington BM, Leveritt MD, Kelly VG. The effect of caffeine on repeat-highintensity-effort performance in rugby league players. Int J Sports Physiol Perform
2017;12:206–10.
56 Bruce CR, Anderson ME, Fraser SF, et al. Enhancement of 2000-m rowing
performance after caffeine ingestion. Med Sci Sports Exerc 2000;32:1958–63.
57 Maughan RJ, Griffin J. Caffeine ingestion and fluid balance: a review. J Hum Nutr
Diet 2003;16:411–20.
58 Rawson ES, Persky AM. Mechanisms of muscular adaptations to creatine
supplementation: review article. Int SportMed J 2007;8:43–53.
59 Volek JS, Rawson ES. Scientific basis and practical aspects of creatine
supplementation for athletes. Nutrition 2004;20(7-8):609–14.
60 Buford TW, Kreider RB, Stout JR, et al. International Society of Sports Nutrition
position stand: creatine supplementation and exercise. J Int Soc Sports Nutr
2007;4:6.
61 Lanhers C, Pereira B, Naughton G, et al. Creatine Supplementation and Upper
Limb Strength Performance: A Systematic Review and Meta-Analysis. Sports Med
2017;47:163–73.
62 Hultman E, Soderlund K, Timmons JA, et al. Muscle creatine loading in men. J Appl
Physiol 1996;81:232–7.
63 Maganaris CN, Maughan RJ. Creatine supplementation enhances maximum
voluntary isometric force and endurance capacity in resistance trained men. Acta
Physiol Scand 1998;163:279–87.
64 Cooper R, Naclerio F, Allgrove J, et al. Creatine supplementation with specific view toexercise/sports performance: an update. J Int Soc Sports Nutr 2012;9:33.
65 Kreider RB, Kalman DS, Antonio J, et al. International Society of Sports Nutrition
position stand: safety and efficacy of creatine supplementation in exercise, sport,
and medicine. J Int Soc Sports Nutr 2017;14:18.
66 Deminice R, Rosa FT, Franco GS, et al. Effects of creatine supplementation onoxidative stress and inflammatory markers after repeated-sprint exercise in humans.
Nutrition 2013;29:1127–32.
67 Schilling BK, Stone MH, Utter A, et al. Creatine supplementation and healthvariables: a retrospective study. Med Sci Sports Exerc 2001;33:183–8.
68 Powers ME, Arnold BL, Weltman AL, et al. Creatine Supplementation Increases Total
Body Water Without Altering Fluid Distribution. J Athl Train 2003;38:44–50.
69 Bailey SJ, Winyard P, Vanhatalo A, et al. Dietary nitrate supplementation reduces theO2 cost of low-intensity exercise and enhances tolerance to high-intensity exercise
in humans. J Appl Physiol 2009;107:1144–55.
70 Thompson C, Wylie LJ, Fulford J, et al. Dietary nitrate improves sprint performanceand cognitive function during prolonged intermittent exercise. Eur J Appl Physiol
2015;115:1825–34.

71 Wylie LJ, Bailey SJ, Kelly J, et al. Influence of beetroot juice supplementation onintermittent exercise performance. Eur J Appl Physiol 2016;116:415–25.
72 Jones AM. Dietary Nitrate Supplementation and Exercise Performance. Sports
Medicine 2014;44:35–45.
73 Bailey SJ, Varnham RL, DiMenna FJ, et al. Inorganic nitrate supplementation improvesmuscle oxygenation, O₂ uptake kinetics, and exercise tolerance at high but not low
pedal rates. J Appl Physiol 2015;118:1396–405.
74 Bailey SJ, Fulford J, Vanhatalo A, et al. Dietary nitrate supplementation enhances
muscle contractile efficiency during knee-extensor exercise in humans. J Appl Physiol
2010;109:135–48.
75 Hoon MW, Jones AM, Johnson NA, et al. The effect of variable doses of inorganic
nitrate-rich beetroot juice on simulated 2,000-m rowing performance in trained
athletes. Int J Sports Physiol Perform 2014;9:615–20.
76 Thompson C, Vanhatalo A, Jell H, et al. Dietary nitrate supplementation improves
sprint and high-intensity intermittent running performance. Nitric Oxide
2016;61:55–61.
77 Jones AM. Influence of dietary nitrate on the physiological determinants of exercise
performance: a critical review. Appl Physiol Nutr Metab 2014;39:1019–28.
78 McMahon NF, Leveritt MD, Pavey TG. The effect of dietary nitrate supplementation
on endurance exercise performance in healthy adults: a systematic review and metaanalysis. Sports Med 2017;47:735-756.
79 Reynolds CME, Halpenny C, Hughes C, et al. Acute ingestion of beetroot juice does
not improve repeated sprint performance in male team sport athletes. Proc Nutr Soc
2016;75:E97.
80 Wylie LJ, Kelly J, Bailey SJ, et al. Beetroot juice and exercise: pharmacodynamic anddose-response relationships. J Appl Physiol 2013;115:325–36.
81 Lancha Junior AH, Painelli VS, Saunders B, et al. Nutritional strategies to modulate
intracellular and extracellular buffering capacity during high-intensity exercise. Sports
Med 2015;45 (Suppl 1):71–81.
82 Saunders B, Elliott-Sale K, Artioli GG, et al. β-alanine supplementation to improve
exercise capacity and performance: a systematic review and meta-analysis. Br J
Sports Med 2017;51.
83 Baguet A, Bourgois J, Vanhee L, et al. Important role of muscle carnosine in rowing
performance. J Appl Physiol 2010;109:1096–101.
84 Chung W, Shaw G, Anderson ME, et al. Effect of 10 week beta-alanine
supplementation on competition and training performance in elite swimmers.
Nutrients 2012;4:1441–53.
85 Nassis GP, Sporer B, Stathis CG. β-alanine efficacy for sports performance
improvement: from science to practice. Br J Sports Med 2017;51.
86 Bellinger PM. β-Alanine supplementation for athletic performance: an update. J
Strength Cond Res 2014;28:1751–70.
87 Hobson RM, Saunders B, Ball G, et al. Effects of β-alanine supplementation on
exercise performance: a meta-analysis. Amino Acids 2012;43:25–37.
88 Katz A, Costill DL, King DS, et al. Maximal exercise tolerance after induced alkalosis.
Int J Sports Med 1984;5:107–10.
89 Mainwood GW, Worsley-Brown P. The effects of extracellular pH and bufferconcentration on the efflux of lactate from frog sartorius muscle. J Physiol
1975;250:1–22.
90 Carr AJ, Hopkins WG, Gore CJ. Effects of acute alkalosis and acidosis on
performance: a meta-analysis. Sports Med 2011;41:801–14.
91 Siegler JC, Marshall PW, Bray J, et al. Sodium bicarbonate supplementation andingestion timing: does it matter? J Strength Cond Res 2012;26:1953–8.
92 Lambert CP, Greenhaff PL, Ball D, et al. Influence of sodium bicarbonate ingestion
on plasma ammonia accumulation during incremental exercise in man. Eur J Appl
Physiol Occup Physiol 1993;66:49–54.
93 Douroudos II, Fatouros IG, Gourgoulis V, et al. Dose-related effects of prolonged
NaHCO3 ingestion during high-intensity exercise. Med Sci Sports Exerc
2006;38:1746–53.
94 Burke LM. Practical considerations for bicarbonate loading and sports performance.
Nestle Nutr Inst Workshop Ser 2013;75:15–26.
95 Mc Naughton L, Thompson D. Acute versus chronic sodium bicarbonate ingestion
and anaerobic work and power output. J Sports Med Phys Fitness 2001;41:456–62.
96 Carr AJ, Slater GJ, Gore CJ, et al. Effect of sodium bicarbonate on (HCO3-), pH, andgastrointestinal symptoms. Int J Sport Nutr Exerc Metab 2011;21:189–94.
97 Requena B, Zabala M, Padial P, et al. Sodium bicarbonate and sodium citrate:ergogenic aids? J Strength Cond Res 2005;19:213–24.
98 He CS, Aw Yong XH, Walsh NP, et al. Is there an optimal vitamin D status for
immunity in athletes and military personnel? Exerc Immunol Rev 2016;22:42–64.
99 Gleeson M, Bishop NC, Oliveira M, et al. Daily probiotic’s (Lactobacillus casei
Shirota) reduction of infection incidence in athletes. Int J Sport Nutr Exerc Metab
2011;21:55–64.
100 Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold.
Cochrane Database Syst Rev 2013;1:CD000980.
101 Nieman DC, Henson DA, McAnulty SR, et al. Influence of vitamin C supplementationon oxidative and immune changes after an ultramarathon. J Appl Physiol
2002;92:1970–7.
102 Walsh NP, Gleeson M, Shephard RJ, et al. Position statement. part one: immune
function and exercise. Exerc Immunol Rev 2011;17:6–63.

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

453

Consensus statement
103 Brinkworth GD, Buckley JD. Concentrated bovine colostrum protein supplementation
reduces the incidence of self-reported symptoms of upper respiratory tract infectionin adult males. Eur J Nutr 2003;42:228–32.
104 Davison G, Diment BC. Bovine colostrum supplementation attenuates the decreaseof salivary lysozyme and enhances the recovery of neutrophil function after
prolonged exercise. Br J Nutr 2010;103:1425–32.
105 Nieman DC, Henson DA, Gross SJ, et al. Quercetin reduces illness but not immune
perturbations after intensive exercise. Med Sci Sports Exerc 2007;39:1561–9.
106 Gleeson M. Immunological aspects of sport nutrition. Immunol Cell Biol
2016;94:117–23.
107 Castell LM, Poortmans JR, Newsholme EA. Does glutamine have a role in reducing
infections in athletes? Eur J Appl Physiol Occup Physiol 1996;73:488–90.
108 Walsh NP, Blannin AK, Robson PJ, et al. Glutamine, exercise and immune function.
Links and possible mechanisms. Sports Med 1998;26:177–91.
109 Dulson DK, Bishop NC. Effect of a high and low dose of caffeine on human
lymphocyte activation in response to antigen stimulation. Appl Physiol Nutr Metab
2016;41:224–7.
110 Walker GJ, Finlay O, Griffiths H, et al. Immunoendocrine response to cycling
following ingestion of caffeine and carbohydrate. Med Sci Sports Exerc
2007;39:1554–60.
111 Linde K, Barrett B, Wölkart K, et al. Echinacea for preventing and treating thecommon cold. Cochrane Database Syst Rev 2006;1:CD000530.
112 Karsch-Völk M, Barrett B, Linde K. Echinacea for preventing and treating thecommon cold. JAMA 2015;313:618–9.
113 Jakeman JR, Lambrick DM, Wooley B, et al. Effect of an acute dose of omega-3 fish
oil following exercise-induced muscle damage. Eur J Appl Physiol 2017;117:575–82.
114 Mickleborough TD. Omega-3 polyunsaturated fatty acids in physical performance
optimization. Int J Sport Nutr Exerc Metab 2013;23:83–96.
115 Meydani SN, Han SN, Hamer DH. Vitamin E and respiratory infection in the elderly.
Ann N Y Acad Sci 2004;1031:214–22.
116 Hemilä H, Virtamo J, Albanes D, et al. Physical activity and the common cold in men
administered vitamin E and beta-carotene. Med Sci Sports Exerc 2003;35:1815–20.
117 Nieman DC, Henson DA, McMahon M, et al. Beta-glucan, immune function,and upper respiratory tract infections in athletes. Med Sci Sports Exerc
2008;40:1463–71.
118 Volman JJ, Ramakers JD, Plat J. Dietary modulation of immune function by betaglucans. Physiol Behav 2008;94:276–84.
119 Harris RC, Söderlund K, Hultman E. Elevation of creatine in resting and exercisedmuscle of normal subjects by creatine supplementation. Clin Sci 1992;83:367–74.
120 Hultman E, Söderlund K, Timmons JA, et al. Muscle creatine loading in men. J Appl
Physiol1996;81:232–7.
121 Rawson ES, Volek JS. Effects of creatine supplementation and resistancetraining on muscle strength and weightlifting performance. J Strength Cond Res
2003;17:822–31.
122 Rawson ES, Clarkson PM, Tarnopolsky MA. Perspectives on exertional
rhabdomyolysis. Sports Med 2017;47:33–49.
123 Gualano B, Rawson ES, Candow DG, et al. Creatine supplementation in the
aging population: effects on skeletal muscle, bone and brain. Amino Acids
2016;48:1793–805.
124 Rae CD, Bröer S. Creatine as a booster for human brain function. How might itwork? Neurochem Int 2015;89:249–59.
125 Rawson ES, Venezia AC. Use of creatine in the elderly and evidence for effects on
cognitive function in young and old. Amino Acids 2011;40:1349–62.
126 Cook CJ, Crewther BT, Kilduff LP, et al. Skill execution and sleep deprivation: effectsof acute caffeine or creatine supplementation - a randomized placebo-controlled
trial. J Int Soc Sports Nutr 2011;8:2.
127 Sakellaris G, Kotsiou M, Tamiolaki M, et al. Prevention of complications related totraumatic brain injury in children and adolescents with creatine administration: an
open label randomized pilot study. J Trauma 2006;61:322–9.
128 Sakellaris G, Nasis G, Kotsiou M, et al. Prevention of traumatic headache, dizzinessand fatigue with creatine administration. A pilot study. Acta Paediatr 2008;97:31–4.
129 Sullivan PG, Geiger JD, Mattson MP, et al. Dietary supplement creatine protects
against traumatic brain injury. Ann Neurol 2000;48:723–9.
130 Szcześniak KA, Ostaszewski P, Fuller JC, et al. Dietary supplementation of β-hydroxyβ-methylbutyrate in animals - a review. J Anim Physiol Anim Nutr 2015;99:405–17.
131 Rowlands DS, Thomson JS. Effects of beta-hydroxy-beta-methylbutyrate
supplementation during resistance training on strength, body composition, andmuscle damage in trained and untrained young men: a meta-analysis. J Strength
Cond Res 2009;23:836–46.
132 Lowery RP, Joy JM, Rathmacher JA, et al. Interaction of beta-hydroxy-betamethylbutyrate free acid and adenosine triphosphate on muscle mass,strength, and power in resistance trained individuals. J Strength Cond Res
2016;30:1843–54.
133 Wilson JM, Lowery RP, Joy JM, et al. The effects of 12 weeks of beta-hydroxy-betamethylbutyrate free acid supplementation on muscle mass, strength, and power inresistance-trained individuals: a randomized, double-blind, placebo-controlled study.
Eur J Appl Physiol 2014;114:1217–27.

454

134 Wilson JM, Lowery RP, Joy JM, et al. β-Hydroxy-β-methylbutyrate free acid reduces
markers of exercise-induced muscle damage and improves recovery in resistancetrained men. Br J Nutr 2013;110:538–44.
135 Phillips SM, Aragon AA, Arciero PJ, et al. Changes in body composition andperformance with supplemental HMB-FA+ATP. J Strength Cond Res 2017:e71–e72.
136 Deutz NE, Pereira SL, Hays NP, et al. Effect of β-hydroxy-β-methylbutyrate(HMB) on lean body mass during 10 days of bed rest in older adults. Clin Nutr
2013;32:704–12.
137 Wilkinson DJ, Hossain T, Hill DS, et al. Effects of leucine and its metabolite
β-hydroxy-β-methylbutyrate on human skeletal muscle protein metabolism. J Physiol
2013;591:2911–23.
138 Barrett EC, McBurney MI, Ciappio ED. ω-3 fatty acid supplementation as a potential
therapeutic aid for the recovery from mild traumatic brain injury/concussion. Adv
Nutr 2014;5:268–77.
139 Erdman J, Oria M, Pillsbury L. Nutrition and traumatic brain injury: improving acuteand subacute health coutcomes in military personnel. Washington, DC: National
Academies Press, 2011.
140 Tipton KD. Nutritional support for exercise-induced injuries. Sports Med 2015;45(Suppl 1):93–104.
141 Lewis M, Ghassemi P, Hibbeln J. Therapeutic use of omega-3 fatty acids in severe
head trauma. Am J Emerg Med 2013;31:273.e5–8.
142 Roberts L, Bailes J, Dedhia H, et al. Surviving a mine explosion. J Am Coll Surg
2008;207:276–83.
143 Smith GI, Atherton P, Reeds DN, et al. Omega-3 polyunsaturated fatty acids augment
the muscle protein anabolic response to hyperinsulinaemia-hyperaminoacidaemia in
healthy young and middle-aged men and women. Clin Sci 2011;121:267–78.
144 Smith GI, Atherton P, Reeds DN, et al. Dietary omega-3 fatty acid supplementation
increases the rate of muscle protein synthesis in older adults: a randomized
controlled trial. Am J Clin Nutr 2011;93:402–12.
145 Gray P, Chappell A, Jenkinson AM, et al. Fish oil supplementation reduces markersof oxidative stress but not muscle soreness after eccentric exercise. Int J Sport Nutr
Exerc Metab 2014;24:206–14.
146 Jouris KB, McDaniel JL, Weiss EP. The effect of Omega-3 fatty acid supplementationon the inflammatory response to eccentric strength exercise. J Sports Sci Med
2011;10:432–8.
147 Close GL, Hamilton DL, Philp A, et al. New strategies in sport nutrition to increase
exercise performance. Free Radic Biol Med 2016;98:144–58.
148 Close GL, Russell J, Cobley JN, et al. Assessment of vitamin D concentration in nonsupplemented professional athletes and healthy adults during the winter months in
the UK: implications for skeletal muscle function. J Sports Sci 2013;31:344–53.
149 Owens DJ, Sharples AP, Polydorou I, et al. A systems-based investigation into vitamin
D and skeletal muscle repair, regeneration, and hypertrophy. Am J Physiol Endocrinol
Metab 2015;309:E1019–31.
150 Owens DJ, Webber D, Impey SG, et al. Vitamin D supplementation does not improve
human skeletal muscle contractile properties in insufficient young males. Eur J Appl
Physiol 2014;114:1309–20.
151 Ruohola JP, Laaksi I, Ylikomi T, et al. Association between serum 25(OH)D
concentrations and bone stress fractures in Finnish young men. J Bone Miner Res
2006;21:1483–8.
152 Lappe J, Cullen D, Haynatzki G, et al. Calcium and vitamin d supplementation
decreases incidence of stress fractures in female navy recruits. J Bone Miner Res
2008;23:741–9.
153 Shaw G, Lee-Barthel A, Ross ML, et al. Vitamin C-enriched gelatin supplementation
before intermittent activity augments collagen synthesis. Am J Clin Nutr
2017;105:136–43.
154 Clark KL, Sebastianelli W, Flechsenhar KR, et al. 24-Week study on the use ofcollagen hydrolysate as a dietary supplement in athletes with activity-related joint
pain. Curr Med Res Opin 2008;24:1485–96.
155 McAlindon TE, Nuite M, Krishnan N, et al. Change in knee osteoarthritis cartilage
detected by delayed gadolinium enhanced magnetic resonance imaging
following treatment with collagen hydrolysate: a pilot randomized controlled trial.
Osteoarthritis Cartilage 2011;19:399–405.
156 McFarlin BK, Venable AS, Henning AL, et al. Reduced inflammatory and muscle
damage biomarkers following oral supplementation with bioavailable curcumin. BBA
Clin 2016;5:72–8.
157 Nicol LM, Rowlands DS, Fazakerly R, et al. Curcumin supplementation
likely attenuates delayed onset muscle soreness (DOMS). Eur J Appl Physiol
2015;115:1769–77.
158 Sciberras JN, Galloway SD, Fenech A, et al. The effect of turmeric (Curcumin)
supplementation on cytokine and inflammatory marker responses following 2 hours
of endurance cycling. J Int Soc Sports Nutr 2015;12:5.
159 Coelho Rabello Lima L, Oliveira Assumpção C, Prestes J, et al. Consumptionof cherries as a strategy to attenuate exercise-induced muscle damage andinflammation in humans. Nutr Hosp 2015;32:1885–93.
160 Bell PG, McHugh MP, Stevenson E, et al. The role of cherries in exercise and health.
Scand J Med Sci Sports 2014;24:477–90.
161 Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis andmeta-regression of the effect of protein supplementation on resistance training-

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

Consensus statement

162
163
164
165
166
167

induced gains in muscle mass and strength in healthy adults. Br J Sports Med
2018;52:376–84.
Cermak NM, Res PT, de Groot LC, et al. Protein supplementation augments theadaptive response of skeletal muscle to resistance-type exercise training: a metaanalysis. Am J Clin Nutr 2012;96:1454–64.
Aguiar AF, Grala AP, da Silva RA, et al. Free leucine supplementation during an
8-week resistance training program does not increase muscle mass and strength inuntrained young adult subjects. Amino Acids 2017;49:1255–62.
Wycherley TP, Moran LJ, Clifton PM, et al. Effects of energy-restricted highprotein, low-fat compared with standard-protein, low-fat diets: a meta-analysis ofrandomized controlled trials. Am J Clin Nutr 2012;96:1281–98.
Krieger JW, Sitren HS, Daniels MJ, et al. Effects of variation in protein andcarbohydrate intake on body mass and composition during energy restriction: ameta-regression 1. Am J Clin Nutr 2006;83:260–74.
Onakpoya I, Hunt K, Wider B, et al. Pyruvate supplementation for weight loss: asystematic review and meta-analysis of randomized clinical trials. Crit Rev Food Sci
Nutr 2014;54:17–23.
Tian H, Guo X, Wang X, et al. Chromium picolinate supplementation for overweightor obese adults. Cochrane Database Syst Rev 2013;11:Cd010063.

168 Jurgens TM, Whelan AM, Killian L, et al. Green tea for weight loss and weight
maintenance in overweight or obese adults. Cochrane Database Syst Rev
2012;12:Cd008650.
169 Kucukgoncu S, Zhou E, Lucas KB, et al. Alpha-lipoic acid (ALA) as a supplementation
for weight loss: results from a meta-analysis of randomized controlled trials. Obes
Rev 2017;18:594–601.
170 Onakpoya IJ, Posadzki PP, Watson LK, et al. The efficacy of long-term conjugatedlinoleic acid (CLA) supplementation on body composition in overweight and obese
individuals: a systematic review and meta-analysis of randomized clinical trials. Eur J
Nutr 2012;51:127–34.
171 Onakpoya I, Posadzki P, Ernst E. The efficacy of glucomannan supplementationin overweight and obesity: a systematic review and meta-analysis of randomized
clinical trials. J Am Coll Nutr 2014;33:70–8.
172 Zhang YY, Liu W, Zhao TY, et al. Efficacy of omega-3 polyunsaturated fatty acids
supplementation in managing overweight and obesity: a meta-analysis ofrandomized clinical trials. J Nutr Health Aging 2017;21:187–92.
173 Jull AB, Ni Mhurchu C, Bennett DA, et al. Chitosan for overweight or obesity.
Cochrane Database Syst Rev 2008;3:Cd003892.

Maughan RJ, et al. Br J Sports Med 2018;52:439–455. doi:10.1136/bjsports-2018-099027

455