|The study at hand used plain ascorbic acid, no quack supplements with "advanced vitamin C".|
When they came up with the study design, Paschalis et al. simply assumed that the mythical ergogenic effect of vitamin C actually existed. To test this hypothesis, they screened 100 males for vitamin C baseline values in blood, picked the 10 individuals with the lowest and the 10 with the highest vitamin C values from their baseline sample and assigned them to two groups.
|Figure 1: Overview of the study design (Paschalis. 2014)|
An overview of the study design is shown in Fig. 1. All measurements were performed between 08:00 and 11:00 h after overnight fasting. Initially, to examine whether rest ing blood vitamin C concentration affects aerobic perfor mance, VO2max was assessed (using incremental cycling test to volitional exhaustion) and was compared in both the low and the high vitamin C groups (Monark, Vansbro, Swe den). More specifially, the protocol started with a 50 W load at 50 rpm and increased by 10 W every 2 min until volitional fatigue. The test was terminated when three of the following four criteria VO2max were met: (1) volitional fatigue, (2) a lower than 2 mL/kg/min increase in VO2 despite an increase in workload, (3) a respiratory exchange ratio greater than or equal to 1.10, and (4) heart rate within 10 bpm of the predicted maximal heart rate (220–age). Res piratory gas variables were measured using a metabolic cart (Quark b2, Cosmed, Italy), which was calibrated before each test using standard gases of known concentration. The VO 2max assessment was used as a reference value to cal culate the workload at the relative intensity of each subject and ensured that all subjects would cycle at similar relative intensity during the following aerobic exercise sessions.After the baseline testing had been done, the subjects within both the low and the high vitamin C groups received either placebo (3x333mg of lactose) or vitamin C supplementation (3x333mg of vitamin C), in a double-blind randomized crossover fashion (see Figure 1).
|Figure 2: Changes in VO2max (left) and redox status (right) in subjects according to initial vitamin C status before and after vitamin C supplementation for 30 days (Paschalis. 2014).|
|Illustration of the relationship between radicals and antioxidants in the determination of redox balance. An increase in radicals or antioxidants results in a disturbance in redox balance (Powers. 2004).|
Moreover, exogenous antioxidants obtained in the diet cooperate with endogenous antioxidants to form a supportive network of cellular protection against radical-mediated oxidative stress. In regard to exogenous antioxidants, a varied diet of fruits and vegetables is a sensible means of obtaining a balance of exogenous antioxidants. In contrast, because of the risk of negative consequences, consuming megadoses of antioxidants via supplements is not recommended" (Powers. 2014 | my emphases).
|Figure 3: Effects of 500mg vitamin C per day on selected parameters in a 4 week chronic exercise + diet supplementation in obese men and women (Huck. 2013)|
This results of stands in contrast to the study at hand, but in line with previous results of studies in athletes, where only more or less irrelevant reductions of the acute inflammatory response to exercise were observed (Nieman. 2000; Peters. 2001; Tauler. 2002). A response of which you as a SuppVersity reader know that it is an essential part of the signalling cascade that triggers the adaptational response to. If we eventually get back to the Paschalis study, it would thus appear that athletes who are usually consuming more than enough vitamin C in their diets and are not at particular risk of developing low serum vitamin C levels would see similar results as the "high vitamin C" subjects in the Paschalis study, i.e. none - even worse, in view of the potential negative effects on the training induced adaptations that could not become visible in the study at hand, because there was no exercise protocol involved, it could even harm their progress.
- Close, G. L., and M. J. Jackson. "Antioxidants and exercise: a tale of the complexities of relating signalling processes to physiological function?." The Journal of physiology 592.8 (2014): 1721-1722.
- Huck, Corey J., et al. "Vitamin C status and perception of effort during exercise in obese adults adhering to a calorie-reduced diet." Nutrition 29.1 (2013): 42-45.
- Nieman, David C., et al. "Influence of vitamin C supplementation on cytokine changes following an ultramarathon." Journal of Interferon & Cytokine Research 20.11 (2000): 1029-1035.
- Paschilis, V. et al. "Low vitamin C values are linked with decreased physical performance and increased oxidative stress: reversal by vitamin C supplementation." Eur J Nutr (2014). Ahead of print.
- Paulsen, Gøran, et al. "Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double‐blind, randomised, controlled trial." The Journal of physiology 592.8 (2014): 1887-1901.
- Peters, E. M., et al. "Vitamin C supplementation attenuates the increases in circulating cortisol, adrenaline and anti-inflammatory polypeptides following ultramarathon running." International journal of sports medicine 22.7 (2001): 537-543.
- Picklo, Matthew. "Supplementation with vitamin E and vitamin C inversely alters mitochondrial copy number and mitochondrial protein in obese, exercising rats (1030.5)." The FASEB Journal 28.1 Supplement (2014): 1030-5.
- Powers, Scott K., et al. "Dietary antioxidants and exercise." Journal of sports sciences 22.1 (2004): 81-94.
- Powers, Scott K., And Kurt J. Sollanek. "Endurance Exercise And Antioxidant Supplementation: Sense Or Nonsense?-Part." Sports Science 27.137 (2014): 1-4.
- Tauler, P., et al. "Diet supplementation with vitamin E, vitamin C and β-carotene cocktail enhances basal neutrophil antioxidant enzymes in athletes." Pflügers Archiv 443.5-6 (2002): 791-797.