Clinical trial NCT03288064: Ergogenic and Antioxidant Effects of Corinthian Currant
Official title: Effects of Corinthian Currant Supplementation on Redox Status, Inflammatory Markers, and Performance During Prolonged Exercise
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Athletic Performance
Oxidative Stress
Inflammation
Keywords: raisins
carbohydrates
antioxidant capacity
substrate oxidation
prolonged cycling
Lead sponsor: University of Thessaly
Sponsor class: OTHER
First posted: 2017-09-19
Enrollment: 11
Sex: ALL
Minimum age (years): 18
Maximum age (years): 45
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: OTHER

Brief summary: The purpose of the present study is to investigate the effect of pre-exercise supplementation of Corinthian currant on metabolism, performance and blood redox status during, and after an acute bout of prolonged exercise.

Methods: Eleven healthy male adults (18 - 45y) performed an acute bout of prolonged cycling in a crossover fashion. Each bout consisted of a 90 min constant-intensity (70 - 75% VO2max) submaximal glycogen depletion trial, followed by a time trial (TT) to exhaustion (95% VO2max), with a wash out period of 2 weeks between bouts. During each experimental condition and 30 min prior to exercise, participants consumed an isocaloric (1.5 g CHO/kg body mass) amount of randomly assigned Corinthian currants, glucose drink, or water. Blood was drawn at baseline, 30 min after the supplement consumption (pre-exercise) and at 30, 60, 90 min of submaximal trial, after TT, and 1 h after the end of exercise (post TT), for the assessment of metabolic changes and redox status alterations.

Detailed description: Aerobic exercise performance in events lasting more than one hour has been shown to improve with pre- or/and during-exercise consumption of carbohydrates (CHO) and athletes or recreationally exercised individuals are often advised to consume CHO before, and/or during exercise. The improvement in performance with CHO supplementation is due to the maintenance of blood glucose levels and the increased CHO availability for oxidation late in exercise that may preserve muscle glycogen. Apparently based on the above mechanisms, the dietary industry provides a wide variety of CHO supplements in different forms (sport drinks, sport gels, CHO bars, sport jellybeans, sport chews). Athletes at all levels use these supplements to optimize their performance during training or competitive events. However, these products are processed, and often expensive, in contrast with other natural foods that may provide an alternative for those preferring a healthier, though, equally effective choice.

Aerobic exercise and training relates with the production of reactive oxygen and nitrogen species (RONS), as indicated by the changes in the concentration of several by-products deriving from the oxidation of biomolecules, and the upregulation of antioxidant enzymes. Although RONS in low to moderate quantities are essential for optimized exercise performance and exercise-induced adaptations, yet, excessive production of RONS especially during exhaustive exercise, promote contractile dysfunction, muscle weakness and fatigue, and impaired recovery from exercise.Therefore, research has focused on nutritional strategies aimed at reducing these effects. There is evidence that treating with antioxidants, protects in part against free radicals-mediated damage in exercise. In regards with this prospective, the supplementation of antioxidants is a very common strategy to minimize RONS production and avoid the detrimental effects of oxidative stress in exercise. In the same way with CHO, natural foods could also provide an alternative antioxidant source for those seeking a more healthy option.

Corinthian currants or Corinthian raisins are small, dark purple colored, sun-dried vine products, produced from a special type of black grape (Vitis Vinifera L., var. Apyrena) and cultivated almost exclusively in the Southern of Greece. Corinthian currants are well known for their potential health benefits. They consist a high source of complex CHO (32.5% glucose, 32.1% fructose, 0.40% sucrose, 0.72% maltose), minerals (magnesium, iron, potassium, phosphorus, zinc) and vitamins (ascorbic acid, pyridoxine, riboﬂavin and thiamin) necessary for vitality, while they contain virtually no fat or cholesterol. Additionally, currants are considered as dried fruits with low to moderate glycemic index despite their high carbohydrate content. Therefore, Corinthian currant could be used as an alternative CHO source during exercise and provide a natural and healthy choice, equally effective to other commercial supplements on favorably affecting metabolism and/or improving performance.

Except for their high CHO content, Corinthian currants are also rich in polyphenols which are free radicals scavenging compounds and provide them with antioxidant properties. The rich antioxidant content renders Corinthian currant a potentially capable nutrient to boost an individual's antioxidant status in response to prolonged aerobic exercise. However, no study so far has addressed this potential role of Corinthian currants.

Therefore, the purpose of the present study was to investigate the effect of pre-exercise supplementation of Corinthian currants on metabolism and performance, as well as redox status in response to prolonged aerobic exercise. These responses were compared against glucose and water.

Eleven healthy well-trained male (n = 9) and female (n = 2) adults (18 - 45y) participated in the present cross over, randomized study. The participants visited the laboratory four times in total. During their ﬁrst visit, anthropometric characteristics assessment and baseline measurements were performed (body mass, standing height, percentage body fat, VO2max). Both the protocol for the assessment of VO2max, and the exercise protocol were performed on a cycle ergometer (Cycloergometer, Monark 834, ERGOMED C, Sweeden). During their second visit, the participants were randomly assigned to either Corinthian currant (1.5 g CHO/kg BW), or glucose drink (1.5 g CHO/kg BW), or water (6ml/kg BW) condition. After the assignment of the experimental condition, the participants performed the exercise protocol which consisted of 90 min of submaximal (70 - 75% VO2max) cycling, followed by a near maximal (95% VO2max) time trial to euxhastion. Fluid intake was kept constant at 7 ml/kg BW before the start of exercise, 3 ml/kg BW every 20 min during the 90-min exercise bout and 7 ml/kg BW within 15 min after the end of exercise. During their third and fourth visits, the participants repeated the experimental procedure after they had been assigned to one of the remaining two conditions. Between the first, second and third visit, there was a wash out period of two weeks. Blood samples were collected at baseline (before the CHO or water consumption), 30 min after CHO or water consumption (pre-exercise) and at 30 min, 60 min, 90 min of submaximal trial, after exhaustion (TT), and 1 h after the end of the exercise, for the assessment of GSH, catalase, uric acid , TAC, and TBARS.

Eligibility criteria: Inclusion Criteria:

* Normal BMI (18.5 - 24.99),absence of lower-limb musculoskeletal injury, absence of any metabolic disease, no drug/supplement consumption, and aerobic fitness (VO2max ≥ 40ml/kg/min at baseline testing).

Exclusion Criteria:

* Abnormal BMI (\<18.5, ≥25), presence of lower-limb musculoskeletal injury, presence of any metabolic disease, no drug/supplement consumption, and aerobic fitness (VO2max \< 40ml/kg/min at baseline testing).

Primary outcomes:
measure: Differences in time trial performance between conditions
timeFrame: After the 90 min submaximal exercise trial
measure: Differences in glucose concentration (GLU) between conditions
timeFrame: At baseline, pre-exercise, 30 min, 60 min, 90 min of submaximal exercise trial, after exhaustion, 1 h post exercise
measure: Differences in lactate concentration (LA) between conditions
timeFrame: AAt baseline, pre-exercise, 30 min, 60 min, 90 min of submaximal exercise trial, after exhaustion, 1 h post exercise
measure: Differences in oxygen consumption (VO2) during exercise between conditions
timeFrame: During the first 15 min of submaximal exercise trial until the desired steady state of VO2 (70% - 75%) was established, and every 25 min for 5 min thereafter
measure: Differences in carbon dioxide (CO2) during exercise between conditions
timeFrame: During the first 15 min of submaximal exercise trial until the desired steady state of VO2 (70% - 75%) was established, and every 25 min for 5 min thereafter
measure: Differences in respiratory quotient (RQ) during exercise between conditions
timeFrame: During the first 15 min of submaximal exercise trial until the desired steady state of VO2 (70% - 75%) was established, and every 25 min for 5 min thereafter
measure: Differences in ventilation (VE) during exercise between conditions
timeFrame: During the first 15 min of submaximal exercise trial until the desired steady state of VO2 (70% - 75%) was established, and every 25 min for 5 min thereafter
measure: Differences in charbohydrates oxidation during exercise between conditions
timeFrame: During the first 15 min of submaximal exercise trial until the desired steady state of VO2 (70% - 75%) was established, and every 25 min for 5 min thereafter
measure: Differences in fat oxidation changes during exercise between conditions
timeFrame: During the first 15 min of submaximal exercise trial until the desired steady state of VO2 (70% - 75%) was established, and every 25 min for 5 min thereafter
measure: Differences in complete blood count (CBC) due to exercise between conditions
timeFrame: At baseline, pre-exercise, 30 min, 60 min, 90 min of submaximal exercise trial, after exhaustion, 1 h post exercise
measure: Differences in reduced glutathione (GSH) (μmol/g Hb) due to exercise between conditions
timeFrame: At baseline, pre-exercise, 30 min, 60 min, 90 min of submaximal exercise trial, after exhaustion, 1 h post exercise
measure: Differences in oxidized glutathione (GSSG) (μmol/g Hb) due to exercise between conditions
timeFrame: At baseline, pre-exercise, 30 min, 60 min, 90 min of submaximal exercise trial, after exhaustion, 1 h post exercise
measure: Differences in thiobarbituric acid-reactive substances, TBARS (μM) due to exercise between conditions
timeFrame: At baseline, pre-exercise, 30 min, 60 min, 90 min of submaximal exercise trial, after exhaustion, 1 h post exercise
measure: Differences in protein carbonyls, (PC) (nmol/mg pr) due to exercise between conditions
timeFrame: At baseline, pre-exercise, 30 min, 60 min, 90 min of submaximal exercise trial, after exhaustion, 1 h post exercise
Secondary outcomes:
Other outcomes:
Locations:
city: Trikala
country: Greece
facility: School of Physical Education and Sport Science, University of Thessaly
state: Thessaly
Study officials:
affiliation: University of Thessaly
name: Athanasios Z Jamurtas, Professor
role: STUDY_CHAIR
References:
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citation: Jeukendrup AE, Killer SC. The myths surrounding pre-exercise carbohydrate feeding. Ann Nutr Metab. 2010;57 Suppl 2:18-25. doi: 10.1159/000322698. Epub 2011 Feb 22.
citation: Chiou A, Panagopoulou EA, Gatzali F, De Marchi S, Karathanos VT. Anthocyanins content and antioxidant capacity of Corinthian currants (Vitis vinifera L., var. Apyrena). Food Chem. 2014 Mar 1;146:157-65. doi: 10.1016/j.foodchem.2013.09.062. Epub 2013 Sep 19.
citation: Too BW, Cicai S, Hockett KR, Applegate E, Davis BA, Casazza GA. Natural versus commercial carbohydrate supplementation and endurance running performance. J Int Soc Sports Nutr. 2012 Jun 15;9(1):27. doi: 10.1186/1550-2783-9-27.