International Journal of Sport Nutrition and Exercise Metabolism, 2019, 29, 198-209
https://doi.org/10.1123/ijsnem.2018-0271© 2019 Human Kinetics, Inc.

SCHOLARLY REVIEWSports Foods and Dietary Supplements for Optimal Function
and Performance Enhancement in Track-and-Field AthletesPeter Peeling
The University of Western Australia and Western Australian Institute of Sport

Linda M. Castell

Wim Derave

Olivier de Hon

University of Oxford

Ghent University

Anti-Doping Authority Netherlands

Louise M. Burke
Australian Institute of Sport and Australian Catholic University
Athletes are exposed to numerous nutritional products, attractively marketed with claims of optimizing health, function, andperformance. However, there is limited evidence to support many of these claims, and the efﬁcacy and safety of many products isquestionable. The variety of nutritional aids considered for use by track-and-ﬁeld athletes includes sports foods, performance
supplements, and therapeutic nutritional aids. Support for sports foods and ﬁve evidence-based performance supplements(caffeine, creatine, nitrate/beetroot juice, β-alanine, and bicarbonate) varies according to the event, the speciﬁc scenario of use,
and the individual athlete’s goals and responsiveness. Speciﬁc challenges include developing protocols to manage repeated use of
performance supplements in multievent or heat-ﬁnal competitions or the interaction between several products which are usedconcurrently. Potential disadvantages of supplement use include expense, false expectancy, and the risk of ingesting banned
substances sometimes present as contaminants. However, a pragmatic approach to the decision-making process for supplement
use is recommended. The authors conclude that it is pertinent for sports foods and nutritional supplements to be considered only
where a strong evidence base supports their use as safe, legal, and effective and that such supplements are trialed thoroughly by
the individual before committing to use in a competition setting.
Keywords: ergogenic aids, performance nutrition, high performance, athletics
Numerous nutritional products are marketed with claims of
optimizing athlete health and function and/or enhancing performance.
Products that fall under the banner of “Sports Foods” or “Dietary
Supplements,” may be used to support performance during training
and competition or for enhancing aspects of training adaptation,
recovery, immune function, and/or overall athlete health. Effective
marketing campaigns and athlete endorsements may convince us thatcertain sports foods and supplements are fundamental in allowing
athletes to reach their sporting goals. However, this approach is naive
in understanding the true foundations of athlete success, such as theinherent genetic predisposition for athletic characteristics, the many
hours of well-structured/periodized training, appropriate underlying
nutrition, adequate sleep and recovery, and of course, good overall
physical and mental health. Nevertheless, if these variables are allaccounted for, there may be a role for sports foods and dietary
Peeling is with School of Human Sciences (Exercise and Sport Science), The Universityof Western Australia, Crawley, Western Australia, Australia; and the Western Australian Institute of Sport, Mt Claremont, Western Australia, Australia. Castell is with Green
Templeton College, University of Oxford, Oxford, United Kingdom. Derave is with theDept. of Movement and Sports Sciences, Ghent University, Ghent, Belgium. de Hon iswith the Anti-Doping Authority Netherlands, Capelle aan den IJssel, The Netherlands.
Burke is with the Australian Institute of Sport, Bruce, Australian Capital Territory,
Australia; and the Mary MacKillop Institute for Health Research, Australian Catholic
University, Melbourne, Victoria, Australia. Address author correspondence to Peter
Peeling at peter.peeling@uwa.edu.au.

198

supplements in an athlete’s training and competition routine, particularly within elite sport where marginal performance gains are pursued.
The following review presents general considerations for track-andﬁeld athletes using sports foods and dietary supplements to enhance
performance, in addition to exploring the potential therapeutic/
prophylactic use of these nutritional aids.

Deﬁnition of a Dietary Supplement
Maughan et al. (2018a) recently deﬁned a dietary supplement as:
A food, food component, nutrient, or non-food compound thatis purposefully ingested in addition to the habitually consumed
diet with the aim of achieving a speciﬁc health and/or performance beneﬁt.

Prevalence
A recent systematic review and meta-analysis of 159 unique studies
in athlete populations (Knapik et al., 2016) investigated theprevalence of dietary supplement use (deﬁned using the Federal
Drug Administration’s Dietary Supplement Health and Education
Act of 1994; e.g., sports foods, iron, vitamins, etc.) by sport, sex,
and athlete status (i.e., elite vs. nonelite). High variability insupplement use among various sporting groups was reported,Sports Foods and Supplements for Athletics

with the combined group summary prevalence estimate (SPE)ranging from 4 to 62% across various supplement types. Whendifferentiated by athlete status, results showed that elite athlete
cohorts (SPE male: ∼69% and SPE female: ∼71%) presented withgreater rates of supplement use than their nonelite counterparts(SPE male: ∼48% and SPE female: ∼42%). Furthermore, sexdifferences were apparent, with greater use of supplemental iron
reported by female athletes, whereas males used products such asprotein, creatine, and vitamin E more often. Although speciﬁc
supplement use among athlete groups is hard to quantify, theseoutcomes suggest that service providers (i.e., dietitians, physiologists, sports physicians) working with athlete cohorts should
be aware of differences in the incidence and type of supplement
use within a given group of athletes, with caliber and sex being
discriminating characteristics. For further insights into the prevalence and rationale for use of supplements and sports foods, thereader is directed to recent comprehensive review of the topic(Garthe & Maughan, 2018).

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Sports Foods
The term “Sports Foods” generally refers to speciﬁcally formulated
food products that are commercially developed for use by athletes.
The various categories of such foods are outlined in Table 1, with a
speciﬁc function to target nutritional goals that underpin training
adaptation, recovery, and competition performance (Burke & Cato,2015). Although they often contain nutrients in similar amounts to
those found in whole foods and manufactured products in thegeneral food supply (hereafter, called “everyday foods”), sports
foods may offer the practical advantage of combining all thenutrients needed for a speciﬁc goal in a single source. In addition,
the use of novel food and packaging technology can make sports
foods easy to transport, store hygienically, prepare, and consume,
Table 1
Product

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particularly in situations before, during, or after/between competition events and training sessions. However, although some sports
foods resemble “everyday food,” they also differ in that they may
consist of only a few nutrients compared with the many hundreds ofnutrients and phytochemicals found in the former. For that reason,
sports foods should not be used as a dietary replacement forathletes, but rather as a supplementary strategy on occasions wherea speciﬁc combination of key nutrients is required.
The ergogenic properties of sports foods, in general, can be
ascribed to four main physiological goals, which they help to
support:a. Hydration: Fluid ingestion for maintaining or restoring hydration status.
b. Fuelling: Carbohydrate provision before, during, and following/
between exercise.
c. Anabolism: Protein ingestion to promote amino acid delivery
for optimal training adaptation and event recovery.
d. Osmolality: Electrolyte ingestion to replenish loss in sweat.
These goals are generally accepted by the broad sport nutrition
scientiﬁc community as being determinants of sports performanceand training response. Of note, the risk of dehydration and fuel/electrolyte depletion is predominately an issue during longer athletic
events, such as distance running and race walking; furthermore, there
is ample evidence of the beneﬁts of hydration, carbohydrate fueling,and electrolyte replacements during these events (Burke, 2010;
Hoffman et al., 2018). Alternatively, athletic sprint events requirea high level of muscle power, and their training-induced muscle
hypertrophy relies on adequate protein and amino acids provision
around training sessions (Reidy & Rasmussen, 2016). Each sports
foods category will contribute to one or more of these physiologicalgoals, yet each in a variable degree. The link between the sports
foods categories and their respective goals is summarized in Table 1.

Summary of the Roles and Ingredients in Sports Foods
Active ingredient

Water

Carbohydrates

ProteinElectrolytes

Physiological goal

Hydration

FuelingAnabolism

Osmolality

✓✓
✓
✓

✓
✓✓

Isotonic sports drink
High-energy sports drinkElectrolyte supplement (drink form)
Sports gel
Protein supplement (drink form)
Sports bars
Sports confectionary
Liquid meal supplements
Advantages of sports foods

Concerns about sports foods

✓
✓
✓✓

✓✓
✓
✓✓
✓
✓
✓
✓
✓✓
✓
✓✓
✓
✓
• Sports foods can contain only those ingredients that are actually needed during exercise.
Foods in the general food supply, particularly whole foods, will usually contain othernutrients, such as fat and ﬁbers, which are not needed during a race, and may cause
gastrointestinal discomfort.
• Sports foods may be manufactured to optimize serving size, convenience, digestibility,
storage, and transport.
• Sports foods are more expensive than “everyday foods” and may drain an unnecessarily
large share of the athlete’s budget. It should be noted that many sports nutrition goals caneasily be met with the use of everyday foods. A typical example is the protein-rich recovery
drinks that can be adequately replaced by the much cheaper dairy products (e.g., skim milk or
yogurt).
• An overreliance on sports foods as energy sources may lead to poor nutrient intake andlimited dietary variety.
✓✓ Can contribute to this goal. ✓✓ Is an important contributor to this goal.
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Of course, manufacturers want to claim additional beneﬁts of
their speciﬁc products and proprietary blends, which usually lackany scientiﬁc substantiation, beyond the beneﬁts of each compoundin isolation. Of note, some manufacturers add performance supplements or other ingredients to sports foods. For instance, protein
shakes can contain creatine, sport drinks or sports bars can containcaffeine, and vitamins can be found in the most unexpected places(e.g., in the so-called “sports/ﬁtness waters” that provide a pleasanttasting drink rather than addressing any unique athlete need). This
makes the distinction between sports foods and sports supplements
more diffuse, and it also greatly complicates the work of sport
nutritionists to keep track of the total daily doses of supplements
and micronutrients to which athletes are exposed. To track the total
ingestion of such ingredients and to reduce concerns aroundproduct contamination via raw ingredients that may be consideredat higher risk of this problem, athletes are guided to choose brandsof sports foods with the simplest formulations to meet the speciﬁcgoals for which they are designed; in general, they should focus
their use of performance supplements to separate protocols, using
separate products, which have preferably been third-party batch
tested or are manufactured by large (reputable) food companies.
The exception to this might be caffeine, which already has acrossover to the food industry, as it is found in the athlete’s diet
via their intake of “everyday-consumer” products, such as coffee,
tea, iced coffee beverages, and “energy drinks.”.
In summary, sports foods may provide a valuable contribution
to an athlete’s nutrition plan, providing nutrients that support
training adaptation (e.g., protein) and promote performance (e.g.,
carbohydrate and ﬂuid/electrolytes). However, their role should not
be overestimated, as many of those goals can, to a large extent, bealso obtained by carefully selected “everyday” foods.

Performance Supplements
Although countless supplements are marketed with the claims of
directly enhancing athletic performance, only a handful are supported by an evidence base that warrants consideration for trial use
by athletes (see Figure 1 relevant to the decision-making process).
A recent review of this area categorizes the commonly encounteredperformance supplements in terms of their research support andlevel of efﬁcacy (Peeling et al., 2018). In addition, the recent
International Olympic Committee consensus statement on supplement use by high-performance athletes (Maughan et al., 2018a)
proposes that only ﬁve performance supplements have an adequatelevel of evidence to suggest marginal performance gains may bepossible for elite athletes (a population where such gains are
generally harder to obtain) when added to a bespoke and periodized
training and nutrition plan. These supplements are summarizedwith the mechanism of action and the potential application to trackand-ﬁeld athletics presented in Tables 2 and 3, respectively.

Caffeine
Caffeine shows well-established beneﬁts for enhancing athletic
performance across both endurance-based events and short-term,supramaximal tasks. Caffeine dosages of 3–6 mg/kg of body mass(BM), consumed ∼60 min prior to exercise in the form of anhydrous caffeine (i.e., pill or powder form), are commonly shown toresult in performance gains (Ganio et al., 2009). However, lower
caffeine doses (<3 mg/kg BM, ∼200 mg), provided both before andduring exercise, have also resulted in an ergogenic beneﬁt (Spriet,2014). Of note, recent research has suggested that the ergogenic

effects of caffeine are inﬂuenced by the athlete’s variant of anumber of genes, including the CYP1A2 gene involved in theliver metabolism of caffeine (Guest et al., 2018). This explains thewell-known variability in individual responses to the “social” useof caffeine, conﬁrming the need for athletes both to trial theirintended performance uses of caffeine prior to implementation incompetition and to take into account their personal history ofreactions to caffeine intake in “everyday life” (e.g., effects onheart rate, jitteriness, or sleep quality). Interestingly, larger caffeine
doses (≥9 mg/kg BM) do not appear to increase the performance
effect (Bruce et al., 2000), and are more likely to increase the riskof negative side effects such as nausea, anxiousness, insomnia,
and restlessness (Burke, 2008). Caffeine habituation seems to have
limited impact on the performance effects of this stimulant(Goldstein et al., 2010); high-habitual daily caffeine users tend
to encounter similar performance beneﬁts as those with low andmoderate intakes (Gonçalves et al., 2017). Furthermore, studies
have shown that athletes need not undertake “caffeine withdrawal”
over the days prior to competition use to achieve a performance
improvement (Irwin et al., 2011). Earlier studies that suggested alarger performance improvement when caffeine supplementation
was preceded by a dehabituation period may have been measuring
the reversal of the negative effects of caffeine withdrawal(i.e., headache, fatigue, demotivation; Irwin et al., 2011) on topof the normal performance effect rather than a unique beneﬁt.
The caffeine supplementation literature shows strong evidenceof improved performance when it is consumed before events
varying in duration from 5 to 150 min (Ganio et al., 2009).
Furthermore, low–moderate doses of caffeine (100–300 mg) consumed during endurance exercise (after 15–80 min of activity)
have also been shown to enhance endurance performance by arange of 3–7% (Paton et al., 2015; Talanian & Spriet, 2016). Whenconsidering short-term, supramaximal tasks, the ingestion of
3–6 mg/kg BM of caffeine taken 50–60 min preexercise relates
to performance gains of >3% for anaerobic activities of 1–2 min induration (Wiles et al., 2006). Therefore, there is support for highperformance track-and-ﬁeld athletes in the longer sprints, middle
distance, and endurance/ultraendurance events to consider competition use of caffeine. Furthermore, shifting the “social” intake of
caffeine to target its effects to training sessions may help toimprove the quality of some workouts, particularly if rehearsing
competition practices or undertaking sessions in a fuel-depleted
state (Lane et al., 2013).

Creatine Monohydrate
Creatine monohydrate (CM) supplementation increases muscle
creatine and phosphocreatine stores, sustaining exercise that isotherwise limited by the inability of phosphocreatine resynthesis tokeep pace with exercise fuel demands, for example, single andrepeated bouts of high-intensity exercise (<150 s duration), with themost pronounced effects evident during tasks <30 s (Branch, 2003;
Lanhers et al., 2017). Indeed, creatine supplementation received
widespread attention in 1992 when the ﬁrst report on successful
loading protocols (Harris et al., 1992) was published at the sametime as anecdotes emerged from the Barcelona Olympic Games
regarding its use by gold-medal winning British track-and-ﬁeld
sprinters. In addition, chronic training adaptations, such as leanmass gains and improvements to muscular strength and power,
have also been noted with both direct and indirect mechanisms
proposed (Table 2). Less commonly, performance advantages forendurance athletes have also been suggested, including suchIJSNEM Vol. 29, No. 2, 2019

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Figure 1 — A pragmatic approach to making decisions about supplement use to optimize function and performance in athletes. Adapted from “IOCconsensus statement: Dietary supplements and the high-performance athlete,” by R. J. Maughan, L. M. Burke, J. Dvorak, D. E. Larson-Meyer, P. Peeling,
S. M. Phillips, : : : L. Engebretsen, 2018a, International Journal of Sport Nutrition and Exercise Metabolism, 28(2), pp. 104–125.

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Table 2

Roles and Challenges of Evidence-Based Performance Supplements
Challenges around use in track-and-field events(Burke, 2017)

Supplement Mechanism of action
Caffeine

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Creatinemonohydrate

Nitrateβ-Alanine

Sodiumbicarbonate• High degree of individual variability includes potential for negative
Caffeine acts as an adenosine receptor antagonist, with many
response, minimal response, positive response, and super response;
effects on different organs and systems. Actions include increases
thorough practice is needed.
in epinephrine release, improvements in neuromuscular function,
vigilance and alertness, and a masking of pain and perception of • Repeated use for events within the same day (e.g., heptathlon anddecathlon) requires careful planning of the timing and amount ofeffort during exercise (Burke, 2008; Spriet, 2014).
doses, including whether a top up dose is even needed.
• Use on successive days (e.g., heats and ﬁnals of many events inmajor meets) requires consideration of the effect on sleep andoverall recovery, especially when the ﬁrst event has a late-nightschedule.
• Interactions with the efﬁcacy or side effects of other supplements
used concurrently needs careful consideration and experimentation;
this is a likely scenario in many events (see Table 3).
Supplementation with creatine monohydrate increases muscle • Weight gain of 1–2 kg associated with creatine supplementation(Buford et al., 2007) may be counterproductive for weight-sensitive
creatine stores and augments the rate of PCr resynthesis,
events, such as jumps and distance races. However, a low-dose
thereby enhancing short-term, high-intensity exercise capacity
approach that avoids the CM “loading phase” may avoid such
(Buford et al., 2007) and the ability to perform repeat highissues (Rawson et al., 2011).
intensity bouts. Chronic effects of increased muscle size andstrength might be explained by indirect beneﬁts (allowing the • Interactions with the efﬁcacy or side effects of other supplements
used concurrently needs careful consideration and experimentation
athlete to train harder) as well as the direct beneﬁts of(see Table 3). Indeed, there has been lengthy but unclear
upregulation of cellular signaling and protein synthesis due to
speculation that the independently achieved performance beneﬁtschanges in cellular osmolality (Safdar et al., 2008). Beneﬁts ofof creatine supplementation might be negated by caffeine
additional muscle storage of glycogen and water might be of
supplementation (Trexler & Smith-Ryan, 2015).
interest to endurance events (Twycross-Lewis et al., 2016).
• As for caffeine, responsiveness to nitrate supplementation is
Nitrate enhances NO bioavailability via the NO3−–nitrite–NO
pathway, which plays an important role in the modulation ofindividual, and protocols for repeated use within the same day needskeletal muscle function (Jones, 2014). This pathway augments
planning. Furthermore, various research suggests a lack of response
exercise performance via an enhanced function of Type II muscle
for athletes with a well-developed aerobic capacity (i.e., VO2max>60 ml/kg; Jones, 2014).
ﬁbers (Jones et al., 2016a), a reduced ATP cost of muscle force
production, an increased efﬁciency of mitochondrial respiration, • Interactions with the concurrent use of other performance supplements
require consideration; at present, this has been investigated in relation
increased blood ﬂow to the muscle, and a decrease in blood ﬂow
to use with caffeine with unclear results (Burke, 2017).
to VO2 heterogeneities (Bailey et al., 2010).
β-Alanine is a rate-limiting precursor to carnosine, an endogenous • Concurrent use of β-alanine and sodium bicarbonate
supplementation is logical when maximal buffering capacity is
intracellular (muscle) pH buffer during exercise (Lancha Juniorneeded; however, literature support for combined beneﬁts is
et al., 2015). Chronic, daily supplementation increases skeletal
premature.
muscle carnosine content (Saunders et al., 2017).
• Potential for gut disturbances is high risk in running-based events,
Sodium bicarbonate acts as an extracellular (blood) buffer,likely due to the increased sodium content and large ﬂuid intake
aiding intracellular pH regulation by raising the extracellularrequired to consume the supplement.
pH and HCO3− concentrations (Katz et al., 1984; Lancha• Protocols for repeated use within the same day or successive days
Junior et al., 2015). The resultant pH gradient between theneed planning.
intracellular and extracellular environments leads to efﬂux
of H+ and La− from the exercising muscle (Katz et al., 1984; • Interactions with the concurrent use of other performance
Mainwood & Worsley-Brown, 1975).
supplements require consideration; concurrent use with caffeine
supplementation has been investigated in other sports and often
seen to counteract the beneﬁts of the former due to gastrointestinalside effects (Burke, 2017).

Note. PCr = phosphocreatine; CM = creatine monohydrate; NO = nitric oxide; ATP = adenosine triphosphate.

beneﬁts as enhanced glycogen storage and thermoregulation secondary to the changes in the cellular environment associated withthe additional storage of creatine and water (Cooper et al., 2012;
Kreider et al., 2017); however, the potential negative inﬂuence ofminor weight gain from such mechanisms should be considered in
the context of event-speciﬁc performance requirements (see Table 2).
Effective supplementation protocols generally encompass a“loading phase” of ∼20 g/day (divided into 4 equal 5 g doses/day),for 5–7 days, followed by a “maintenance phase,” typicallyinvolving a single daily CM dose of 3–5 g for the duration of
the supplementation period (Hultman et al., 1996). Alternative
approaches propose lower doses of CM (2–5 g/day), consumed forapproximately 4 weeks (Rawson et al., 2011), based on the conceptthat low doses of CM provided over an adequate time period canincrease muscle creatine levels (Hultman et al., 1996). Of note,
consuming CM concurrently with a mixed protein/carbohydrate
source (∼50 g of protein and carbohydrate) may enhance muscle
creatine uptake via insulin stimulation (Steenge et al., 2000), while
it takes ∼4–6 weeks following the cessation of supplementation formuscle stores to return to baseline levels.
No negative health effects have been noted with the long-term
use of CM (up to 4 years) when appropriate loading protocols arefollowed (Schilling et al., 2001), and in some instances, potential
anti-inﬂammatory effects are proposed (Deminice et al., 2013).
Therefore, creatine supplementation consumed according to thepreviously mentioned protocols shows strong efﬁcacy for bothIJSNEM Vol. 29, No. 2, 2019

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Table 3 Performance Supplements That May Achieve a Marginal Performance Gain in Track-and-Field Eventsas Part of a Bespoke and Periodized Training and Nutrition Plan
Event
Sprints: 100 m, 100-m hurdles, 110-m hurdles, and 200 m
Sustained sprints: 400 m and 400-m hurdles
Middle distance: 800 m, 1,500 m, 3,000 m, and steeple chaseLong distance: 5,000 m, 10,000 m, cross-country, 20-km race walk, half
marathon, marathon, 50-km race walk, and mountain/ultra running
Jumps and throws: high jump, long jump, triple jump, pole vault, discus throw,
hammer throw, javelin throw, and shot put
Multievents: heptathlon and decathlon

Caffeine

Creatine

✓
✓
✓
✓

✓
✓

✓

✓

✓

✓

Nitrateβ-Alanine

Bicarbonate

✓
✓

✓
✓

✓

✓

✓
✓

✓

Readers are referred to Burke et al. (2019), da Costa et al. (2019), Slater et al. (2019); Stellingwerff et al. (2019), and Sygo et al. (2019).

acute and chronic performance gains, where power, strength, andshort-repeated bouts of high-intensity exercise are encountered.

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NitrateNitrate supplementation has been shown to promote improvements
in exercise tasks that predominately stress the aerobic energy
system, such as time to exhaustion (4–25% increased performance)and sport-speciﬁc events (1–3% increased performance) lasting<40 min (Jones, 2014; McMahon et al., 2017). In addition, nitrate
supplementation is proposed to enhance Type II muscle ﬁber
function (Bailey et al., 2015) resulting in the improvement (3–5%)
of high-intensity exercise efforts (Thompson et al., 2015; Wylie
et al., 2016). Current evidence is equivocal for such beneﬁt to
exercise tasks lasting <12 min (Reynolds et al., 2016; Thompson
et al., 2016), although more work is needed in this area.
Nitrate-rich foods include leafy green and root vegetables(i.e., spinach, rocket, celery, beetroot, etc.), although beetroot juice
is the more popular supplement choice for exercise settings(McMahon et al., 2017). Acute performance beneﬁts are generally
seen within 2–3 hr following a NO3− bolus of 5–9 mmol (310–560 mg) (Hoon et al., 2014; Peeling et al., 2015); however, chronic
periods of NO3− intake (>3 days) also appear beneﬁcial to performance (Thompson et al., 2015, 2016).
There appears to be few side effects or limitations to nitrate
supplementation other than the potential for minor gastrointestinal
upset in some gut-sensitive athletes. In addition, an upper limit tothe beneﬁts of NO3− consumption has been shown (i.e., no greater
beneﬁt from 16.8 mmol [1,041 mg] vs. 8.4 mmol [521 mg]; Wylie
et al., 2013), and it might also be considered that performancegains appear harder to obtain in elite athletes, with limited to no
beneﬁts generally seen in athletes with a maximal oxygen uptake(VO2max) > 60 ml/kg (Jones, 2014). Therefore, individual trials of
this supplement prior to use in competition are recommended toensure its use is effective.

β-Alanineβ-Alanine supplementation is associated with the improved tolerance for maximal exercise in the range of 30 s to 10 min (Saunders
et al., 2017), with small but potentially meaningful performance
beneﬁts (∼0.2–3%) shown during both continuous and intermittent
exercise tasks of this duration (Baguet et al., 2010; Chung et al.,2012). β-Alanine supplementation increases the muscle content ofcarnosine, an intracellular dipeptide with buffering, antioxidant,
and anti-inﬂammatory properties. Of these effects, enhanced buffering is believed to explain the main performance beneﬁt.

β-Alanine dosing strategies typically involve the consumption of
3.2–6.4 g/day, ingested via a split-dose regimen (i.e., 0.8–1.6 g every
3–4 hr) over an extended supplement time frame of 4–12 weeks(Saunders et al., 2017). Regardless, a positive correlation between themagnitude of muscle carnosine change and performance beneﬁt
remains to be established (Saunders et al., 2017). Of note, theeffectiveness of this supplement has also been shown in well-trained
athletes (Bex et al., 2014; Saunders et al., 2017), although theperformance margins for improvement are evidently smaller(Bellinger, 2014). A possible negative side effect of skin paresthesia
should be considered, although sustained release tablets are noted toprevent this outcome and are reported to result in lower urinary loss ofthe supplement, possibly resulting in improved whole-body β-alanine
retention (Decombaz et al., 2012). Finally, large interindividual
variations in muscle carnosine synthesis have been reported withthe use of β-alanine (Stautemas et al., 2018), and therefore, anindividualized approach to supplementation must be considered.

Sodium Bicarbonate
Sodium bicarbonate (NaHCO3) supplementation is proposed toenhance the performance (∼2%) of short-term, high-intensity
sprints lasting ∼60 s in duration, with a reduced efﬁcacy as theeffort duration exceeds 10 min (Carr et al., 2011a). In contrast to
β-alanine supplementation, which achieves a chronic elevation in
intracellular buffering capacity, NaHCO3 ingestion (consumed at adose of 0.2–0.4 g/kg BM) achieves an acute increase in extracellular/
blood buffering (Carr et al., 2011a) with peak blood bicarbonate
levels occurring after 75–180 min (when consuming 0.3 g/kg BM
NaHCO3), which appear to decrease by 3-hr postsupplementation(Jones et al., 2016b). However, split doses (i.e., several smaller
doses) taken over a 30- to 60-min time period (Krustrup et al., 2015)or serial loading with three to four smaller doses per day for two tofour consecutive days prior to an event (Burke, 2013) has been
proposed as methods to overcome the well-established gastrointestinal distress associated with this supplement. Further strategies
used to minimize gastrointestinal distress include the coingestionof NaHCO3 with a small carbohydrate-rich meal (∼1.5 g/kg BM
CHO; Carr et al., 2011b) or the use of the less effective but more
gut-friendly sodium citrate as an alternative (Requena et al., 2005).
In summary, despite the relatively robust evidence base tosupport the consideration for use of these ﬁve supplements by welltrained athlete populations, the potential side effects and negative
individual tolerance must be considered, and therefore, any supplement use should be thoroughly trialed in training before competition. Notwithstanding, as can be seen in Table 2, there arepotential challenges for the use of these supplements within

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track-and-ﬁeld events, including issues of repeated use and thepotential for interaction when several potentially useful supplements
are used together (Burke, 2017). The current literature relevant tosuch use is not well understood and requires more research.

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Therapeutic Nutritional Supplements
and Prophylactic Aids
In the context of this review, “therapeutic/prophylactic supplements” are considered as nutritional aids that can be used either to(a) correct a deﬁciency, (b) assist in the possible prevention ofillness and/or injury, or (c) help in the recovery from the stress ofphysical workloads via an anti-inﬂammatory effect. For instance, itis well known that iron deﬁciency can impair hematologic adaptation, which left untreated can negatively impact on athletic performance (Garvican et al., 2011). However, nutritional correction ofthis issue via various intervention strategies has been regularly
shown to have a positive impact on correcting the underlying
deﬁciency and enhancing athlete performance (Dawson et al.,2006; Garvican et al., 2011; Woods et al., 2014).
Regarding illness, there is strong evidence to suggest that
immunodepression can occur as a result of strenuous exercise(Castell et al., 2019; Peake et al., 2017), and a high incidenceof upper respiratory tract illness is frequently reported (Drew et al.,2018; Nieman, 1994), before and particularly after endurance
events. Low-energy availability has been identiﬁed as a key
nutritional factor in such illness (Drew et al., 2018; Heikura
et al., 2018); however, the provision of nutritional supplements
to alleviate exercise-induced immunodepression and to aid more
rapid recovery in athletes has also been well studied. Sometimes
certain supplements initially appear promising, but further intensive investigation fails to provide sufﬁcient evidence of consistentbeneﬁcial effects on some aspects of exercise-induced immunodepression. As different nutritional supplements become unfashionable, whether targeting immunodepression or performance,others take their place; however, the pros and cons of theseneed to be carefully studied. For instance, probiotic supplementation has been investigated in recent years (as have prebiotics), withpreliminary evidence of positive effects on immune function (Coxet al., 2010) that might support the consistency of training andcompetition. However, the effects of such supplementation are
dependent on appropriate doses of live bacteria of speciﬁc strains(e.g., Lactobacillus, Biﬁdobacterium), and larger studies are stillneeded to provide deﬁnitive evidence that probiotics beneﬁt theimmune function of athletes. Glutamine and branched chain aminoacids, which are often marketed to support bodybuilding andpostexercise recovery, also have an unclear role in supporting
immune function in athletes (Bermon et al., 2017). Clearly, immunonutrition is an emerging and important area for considerationin the use of dietary supplements for athlete populations, and assuch, the reader is directed to recent reviews in this area (Bermon
et al., 2017; Castell et al., 2019), in addition to the comprehensive
paper on feeding the immune system (Calder, 2013).
With respect to the inﬂammatory response, there is a growing
body of work that is investigating anti-inﬂammatory and antioxidant aspects of various foods and supplements. For instance, foodpolyphenols possess strong antioxidant and anti-inﬂammatory
properties (Tsao, 2010) that may be beneﬁcial to exercise recovery.
Speciﬁcally, the high-anthocyanin content of tart Montmorency
cherries is proposed to reduce the inﬂammatory and oxidative
stress responses to strenuous exercise, such as a marathon(Dimitriou et al., 2015; Howatson et al., 2010), or consecutive
days of intermittent high-intensity activity (Bell et al., 2014). Thismay be particularly relevant to the heavy training loads of manyhigh-performance athletes, as well as the competition recovery inmultievents in track-and-ﬁeld athletics or the programs of middledistance runners with heats and ﬁnals across several events at major
competition. Other anti-inﬂammatory nutrients include ﬂavonoids
such as quercetin and green tea extract, plus ﬁsh oil, each of which
may have a beneﬁcial effect on delayed onset muscle soreness(Ranchordas et al., 2018). Consumption of highly colored vegetables/fruit is often advised; this advice is appropriate for elite
athletes (previously mentioned), as these ﬂavonoids (including
blueberries, blackcurrants, and cherries) have a beneﬁcial effecton exercise-induced inﬂammation, muscle damage, and illness(Bermon et al., 2017). In addition, it is proposed that some ofthese foods may also have the ability to reduce exercise-induced
oxidative stress; however, there is currently some controversy
about whether high-dose antioxidant supplementation (in theform of pills, powders, and tablets) is advisable to alleviate
exercise-induced generation of reactive oxygen/nitrogen species.
Emerging evidence suggests that antioxidant supplementation
mitigates important exercise-induced adaptations, which may
also extend to the immune system (Bermon et al., 2017).
In summary, there are various roles for nutritional supplements
for what may be considered “therapeutic applications”; however,much more work is needed in this area to assess the efﬁcacy ofthese supplements and to determine their true effect on athletic
performance.

Disadvantages of Sports Foods
and Dietary Supplements
The decision to take a supplement will always involve an attempt togain a functional advantage, in most cases being health protection/
improvement, physique management or enhanced recovery, or adirect performance enhancement. Contrary to these potential beneﬁts,
is the consideration that the supplement inherently possesses certain
risks against its use; such risks can be divided into three categories.

Risks of Labeled Content
All supplements worldwide are legally bound to be sold in
packages that contain a listing of the ingredients. Some national
legislations may be stricter than others in setting and enforcing
the list of permitted ingredients in supplements, but any consumer,
and certainly, athletes who consider taking supplements to support
their athletic performance should not consume a product withingredients that cannot be recognized in a basic Internet search.
A so-called “proprietary-blend” listing exotic names and claiming
commercial Intellectual property cannot be considered a transparent listing of ingredients.
Even when supplement contents are clearly listed, they cannot
necessarily all be considered safe. In many countries, the regulations
covering supplements do not require speciﬁc testing before going tomarket but rely on notiﬁcation of adverse events to remove unsafe
products from sale. This has led to the inclusion of toxic substancesin highly popular products, for example, the bodybuilding andweight loss supplement OxyELITE Pro (USPlabs, Hermosa
Beach, CA) was found to be associated with at least one death anda cluster of serious liver complications, attributed to the ingredient
1,3-dimethylhexanamine (also known as DMAA; Johnston et al.,2016). This was subsequently removed from the list of ingredientsIJSNEM Vol. 29, No. 2, 2019

Sports Foods and Supplements for Athletics

that may be included in supplements across many countries. Even
where some ingredients might have been considered to be “safeuse,” basic toxicology laws dictate that any substance has thepotential to lead to health-deteriorating effects when used bysome individuals in speciﬁc scenarios or doses. For athletes, thisis often preceded by decreased performance.

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Risks of Undeclared or Unlabeled Content
Despite existing legislations, some supplements have been found tocontain contaminants or health hazards, such as molds, glass, oranimal feces (Benedict et al., 2016; Katz, 2013). A speciﬁc risk forcompetitive athletes is the undeclared presence of substances thatare banned under the World Anti-Doping Agency (WADA) antidoping code. Of course, these substances are sometimes identiﬁed
on product labels, but athletes are either unaware that they arebanned or are confused by technical/chemical names. For example,
DMAA is a banned substance and has been included in supplements under a variety of other names including geranium oil/extract or geranamine; this no doubt contributed to many publicized and less well-known cases of anti-doping rule violations.
This risk of inadvertent doping from supplement use has been
known for at least 30 years but is still very much present (de Hon &Coumans, 2007; Geyer et al., 2004; Martinez-Sanz et al., 2017).
Indeed, the list of prohibited substances that have been detected insupplements includes stimulants, anabolic agents, selective androgen receptor modulators, diuretics, anorectics, and β2 agonists(Martinez-Sanz et al., 2017). When the amounts of banned substances in supplements are large enough to generate a direct effect(e.g., stimulant symptoms), this is an obvious sign of potential
contamination to a consumer and sometimes an indicator of intentional but undeclared manufacturing practices (Geyer et al., 2008;
Parr et al., 2007, 2008). But the risks of unintentional contaminationfrom adulterated raw ingredients or cross-contamination of machinery, even by the most careful manufacturers, should not be underestimated and will never be zero (Judkins et al., 2010; Maughan
et al., 2018b). Because of the ever-improving analytical capabilities
in antidoping laboratories, trace amounts of prohibited substances
can be found in biological samples taken at doping control. As aresult, it cannot be stressed enough that athletes need to be awarethat the WADA rules of strict liability mean that the detection of aprohibited substance in an athlete’s specimen will be treated as
an anti-doping rule violations, irrespective of the intentions behindit (Abbott, 2004; Hughes, 2015). Furthermore, it should also be
understood that coaches, support personnel, parents, friends, andanyone else involved in the life of an athlete can also be implicatedin an anti-doping rule violations, with WADA imposed sanctions(i.e., suspensions from sport) applicable. Using only products thathave been audited by a third-party testing program and found to be
free of banned substances will help to lower, but not completely
eliminate, this risk. However, the general avoidance of the high-risk
multi-ingredient supplements promoted as preworkouts or weightloss and bodybuilding products is recommended.

205

especially when ﬁnite resources could have been used in otherareas of the preparation of an elite athlete’s life. Finally, concerns
have been raised that supplement use may be a stepping stone totaking other substances, including those prohibited by antidoping
regulations (Backhouse et al., 2013). With this in mind, attention
should be directed toward the ethical challenges of athlete productmarketing and the inﬂuence of such approaches on encouraging
undue supplement use, especially on young/developing athletes.
In summary, the very real risks of taking supplements should be
carefully considered by competitive athletes. Of note, Castell et al.
(2015) published an A–Z Guide on 140 nutritional supplements inexercise and health; this includes efﬁcacy tables ranging from those
supplements shown to be ergogenically effective to those banned by
WADA as being harmful or illegal. Readers might ﬁnd it useful toconsult this book prior to embarking on a course of supplements.

Conclusion: A Pragmatic Approach to
Making Decisions about Supplements
In the past, athletes and coaches often worked in a parallel universeto their expert groups (e.g., governing bodies of sport) and service
teams (e.g., sports scientists, dietitian, and physicians) with regard
to performance supplements, with the former favoring supplement
use based on their interest in performance gains and the latter being
risk averse and dismissive of such products. The modern landscape,at least for high-performance athletes, has seen a uniﬁcation ofeffort and intent, with many parties now working together to take apragmatic approach to managing a risk:beneﬁt audit around the useof sports foods, therapeutic/prophylactic supplements, and performance supplements. This has been led by organizations such as
the International Olympic Committee and the Australian Instituteof Sport, that have produced expert statements (Maughan et al.,2018a) and education resources (Burke & Cato, 2015) to guide aproactive but evidence-based consideration of the use of theseproducts. In the case of sports foods, track-and-ﬁeld athletes are
guided to seek the expertise of an appropriately qualiﬁed sports
nutrition professional who can help them balance the expense ofusing these specialized products with the scenarios in which
they offer genuine performance beneﬁts. Therapeutic/prophylactic
supplements should involve the expertise of a sports physician,especially when a diagnosis of medical issues and nutrient deﬁciencies is needed. A decision-tree approach to the use of performance supplements (Figure 1), especially in collaboration withsports science/nutrition experts, will help to ensure that any
products that are used are appropriate to the athlete’s age andmaturation in their event, integrated into the athlete’s plan according to evidence-based protocols and appropriate scenarios, andchosen on the basis of being at low risk of contamination withbanned or harmful ingredients. Ultimately, it is pertinent that sports
foods and nutritional supplements should only be considered wherea strong evidence base supports their use as safe, legal and effective
and that such supplements are trialed thoroughly by the individual
before committing to use in a competition setting.

Noncontent-Related Risks
Some ﬁnal concerns or issues regarding use of supplements andsports foods need to be considered. First, athletes should realizethat any beneﬁt of legal supplementation is bound to be small.
Expecting too much of an intervention that addresses only the top
end of one aspect of athletic performance may lead to disappointments and distract from other, more powerful, aspects of elite
athletic training. Second, expense must also be considered,

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