I read an article in the NY Times that surprised me about this subject.
I'll quote some of it, and you can google the article if interested
FEB 12, 12:01 AM
Why Vitamins May Be Bad for Your Workout
By GRETCHEN REYNOLDS
Many people take vitamins as part of their daily fitness regimens, having heard that antioxidants aid physical recovery and amplify the impact of workouts. But in another example of science undercutting deeply held assumptions, several new experiments find that antioxidant supplements may actually reduce the benefits of training.
Antioxidants became popular dietary supplements largely because they were said to sop up free radicals, the highly reactive oxygen molecules that are generated during daily activities. Physical exertion, through its breakdown of oxygen, results in the creationof large numbers of these molecules, which, in excess, can lead to cell death and tissue damage. So it seems logical that reducing the number of free radicals produced by exercise would be desirable.
Enter antioxidants, which absorb and deactivate free radicals. While the body creates its own antioxidants, until recently many researchers believed that we produce too few natural antioxidants to counteract the depredations from free radicals created during exercise. So many people who exercise began downing large doses of antioxidants such as vitamins C and E, even though few experiments in people had actually examined the precise physiological impacts of antioxidant supplements in people who work out.
For a study published last week in The Journal of Physiology, researchers with the Norwegian School of Sport Sciences in Oslo and other institutions gathered 54 healthy adult men and women, most of them recreational runners or cyclists, and conducted a series of tests, including muscle biopsies, blood draws and treadmill runs, to establish their baseline endurance capacity and the cellular health of their muscles.
Then they divided the volunteers into two groups. Those in one group took four pills a day, delivering a total dose of 1,000 milligrams of vitamin C and 235 milligrams of vitamin E. Members of the second group got identical placebo pills.
Finally, they asked all of the participants to complete a vigorous 11-week training program, consisting of increasingly intense interval sessions once or twice per week, together with two weekly sessions of moderately paced hour-long runs. By the end, all of the volunteers were more fit than they had been at the start, with their maximum endurance capacity increasing by an average of about 8 percent.
But their bodies had responded quite differently to the training. The runners who had swallowed the placebo pills showed robust increases of biochemical markers that are known to goose the creation of mitochondria, the tiny structures within cells that generate energy, in cells in their bloodstream and muscles. More mitochondria, especially in muscle cells, means more energy and, by and large, better health and fitness. The creation of new mitochondria is, in fact, generally held to be one of the most important effects of exercise.
But the volunteers who had consumed the antioxidants had significantly lower levels of the markers related to mitochondrial creation. The researchers didn’t actually count the specific populations of mitochondria within their volunteers’ muscles cells, but presumably, over time, those taking the antioxidants would see a smaller uptick in mitochondrial density than among those not taking them.
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I didn't get to the comments on the article, so there may be some interesting takes found in those.