Tuesday, December 23, 2014

First Human Study to Confirm That Repleting Low Vitamin C Levels W/ 1g Vitamin C Boosts Aerobic Performance

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 | Comment on Facebook!
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