 |
The study at hand used plain ascorbic acid, no quack supplements with "advanced vitamin C". |
While people tend to believe that vitamin C is good for anything, the evidence that it actually does anything good is relatively scarce. Against that background I am happy to tell you that a group of Greek researchers from the
School of Physical Education and Sport Science, the
European University Cyprus and the
Aristotle University of Thessaloniki have now finally confirmed what many of you probably thought was a long-established fact: "[L]ow vitamin
C concentration is linked with decreased physical performance and increased oxidative stress and that vitamin
C supplementation decreases oxidative stress and might
increase exercise performance only in those with low initial
concentration of vitamin C." (Paschalis. 2014)
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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) |
Using a placebo-controlled crossover design, the 20 selected subjects performed aerobic exercise to exhaustion (oxidant
stimulus) before and after vitamin C supplementation for 30 days.
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). |
As you can see in
Figure 2 there were measurable differences in the response to the acute exhaustive exercise protocol (an
oxidant stimulus), the subjects in both groups performed before and after vitamin C or placebo
supplementation for 30 days. The data in
Figure 2 does yet also show that the subjects who had been randomly assigned to the vitamin C supplement group had lower baseline VO2max levels. A fact that raises the question whether this is the result of a lower vitamin C intake or whether the vitamin C intake correlates with an unhealthier lifestyle that left the subjects unfit and with low vitamin C levels.
 |
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). |
So what, to supplement with antioxidants or not? I have voiced my opinion often enough and still people ask me time and again whether it "may not be a good idea to..." Against that background I will not repeat myself, but quote someone else, Scott K. Powers and Kurt J. Sollanek who wrote an extensive review of the literature for one of the latest issue of the
Sports Science Exchange: "Exercise promotes radical production in the working muscles and
prolonged/intense exercise can produce an imbalance between
radical production and muscle antioxidants altering the “redox
balance” and resulting in oxidative stress. To protect against radical
mediated damage, muscle cells contain endogenous antioxidants
to scavenge radicals.
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).
Unfortunately, this question is hard to answer based on the available research on vitamin C. While we have conflicting results with respect to its ability to impair the adaptational response to exercise (Close. 2014), there is very little evidence that it will actually have beneficial effects on any meaningful performance parameters. In fact, a study by Huck et al. that was published in the scientific journal
Nutrition in 2013 is probably what comes closest to the results of the study at hand.
 |
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) |
In said study Huck et al. observed that the provision of 500mg of vitamin C as an adjunct to exercise and diet in obese individuals lead to significant reductions in heart rate and the ratings of perceived exertion during exercise. The data in in
Figure 3 does yet also tell you that there were no beneficial effects on VO2max, which best reflects the adaptational response to exercise.
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.
Bottom line: Just like the researchers had expected, they found higher resting levels
of oxidative stress and decreased exercise performance
in the individuals with low baseline values of vitamin C
compared to those with high vitamin C values.
 |
Figure 3: Rel. changes in PGC-1α in
cytosolfractions in the vitamin C and E group and
the placebo group of a randomized controlled antioxidant + exercise study by Paulsen et al. (2014) - find out what boosts PGC-1α | here. |
Since the provision of 1g of vitamin C oxidative stress, it is thus not surprising that there was a concomitant increase in exercise performance. What is "surprising", though, is that the latter was "marginally" and clearly "non-signifiant." Furthermore, it was observed only in those individuals with a poor initial vitamin C status. In that, it is a novel finding that you do not need to suffer from hypovitaminosis C (<23µmol/L) or vitamin C deficiency to be
derive acute benefit from vitamin C supplementation as regards to redox
status and physical performance. Previous studies which combined the provision if vitamin C with chronic exercise training, however, indicate that the ingestion of anti-oxidants can blunt the intra-cellular adaptive responses to exercise (Paulsen. 2014) - an effect that obviously couldn't be confirmed or negated in the study at hand, because it lacks a chronic exercise component |
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References:
- 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.