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High doses of vitamins C and E not harmful to athletes
High doses of vitamin C and E, both antioxidants, can inhibit the body’s adjustment to physical training, wrote German nutritionists last spring in the prestigious PNAS. But according to a broader Danish study, soon to be published in Medicine & Science in Sports & Exercise, the news is not so bad. The Danes did not discover a single negative effect of vitamin C or E. But they didn’t discover any positive ones either.
Physical exercise increases the production of free radicals – which are bad news on the health front. Dr Kenneth Cooper, inventor of the Cooper test and a strong proponent of physical exercise, was therefore a big supporter of antioxidant vitamins for endurance athletes. But recent studies indicate that they have no effect. According to these studies, the human body is perfectly capable of adjusting to an increase in the manufacture of free radicals on its own. Taking antioxidant vitamins can mess up the body’s ability to adjust. That was the line taken in the German research we mentioned above.
In the German study the researchers got their test subjects to do an hour of fitness training daily for four weeks, and gave them 1 gram vitamin C and 400 IE vitamin E. The Danes went for a more thorough approach. They got 11 young men to cycle every day for 12 weeks and to follow a high volume training programme. The test subjects in the experimental group took half a gram of vitamin C and 400 IE of vitamin E every day. The placebo group consisted of 10 test subjects who followed the same programme.
By the time the 12 weeks were up, the bodies of the subjects in the experimental group and the placebo group had adjusted to the training. However, there were no significant differences between the groups. The figure below shows the maximal oxygen consumption of both groups. This is a measure of stamina.
Analyses of muscle tissue showed that that the muscle cells in both groups had started to retain more glycogen. And taking antioxidant vitamins had no effect on this.
As a result of training, the mitochondria start to produce more enzymes that can convert fats, carbohydrates and proteins into energy. One of these is citrate synthase, a key enzyme in the citric acid cycle. The production of this enzyme rose by a similar amount in both groups.
Muscle cells respond to continuous training by producing more protective enzymes. One of these is manganese superoxide dismutase. The figure below shows that the production of this enzyme increased by similar amounts in both groups.
After the worrying news from Germany, supplements users in the western world will probably receive the Danish publication with a sigh of relief. However, the Danes themselves regard their findings as an argument for athletes not to use vitamins C and E.
"Considering that the health conscious part of the population generally consumes a balanced diet, rich in fruits and vegetables, our data suggest that this population will not experience any effect - positive or negative - from moderate daily vitamin supplements on training adaptation in response to strenuous endurance training", concluderen ze. "In conclusion, healthy people who just exercise regularly should be more critical towards antioxidant supplements."
Source:
Med Sci Sports Exerc. 2009 Dec 14. [Epub ahead of print].
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