Ergogenic and Antioxidant Effects of Corinthian Currant
Condition: Athletic Performance; Oxidative Stress; Inflammation
MeSH terms: Inflammation
Study type: Interventional

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.
    

Intervention name(s): Corinthian currant; Glucose drink; Water ingestion
Intervention type(s): Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): Supplementation of 1.5 g CHO/kg BW in the form of Corinthian currant prior to exercise; Supplementation of 1.5 g CHO/kg BW in the form of glucose drink prior to exercise; Supplementation of 7ml/kg BW prior to exercise
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Other
Keywords: raisins; carbohydrates; antioxidant capacity; substrate oxidation; prolonged cycling