The Use of Antioxidant Vitamins For Exercise Performance
The effect of exercise on the body could perhaps be seen as a case of “tough love.” Exercise actually causes damage to the body at the cellular level, something that can be felt at the human level as sore muscles after an intensive exercise bout. This damage is necessary to stimulate the body to rebuild stronger and more efficient muscle tissue. Improvements in physical performance, and the health benefits of exercise, therefore only arise after the body is damaged by exercise.
The cellular damage is caused by oxidative stress. In the case of exercise, the oxidative stress is caused by the intensive energy use by muscles. As antioxidant vitamins are capable of reducing levels of oxidative stress, it is thought that muscle pain can be reduced. Less muscle pain after exercise allows athletes to train harder. Various studies have therefore investigated whether antioxidant supplements provided at levels higher than what can be obtained through the diet can affect exercise performance. The authors Draeger et al. aimed to summarize studies conducted with antioxidant vitamins on physical performance.
The authors identified a few small studies have been conducted in both trained athletes and untrained volunteers. This is an important distinction to make, because people who exercise regularly have higher levels of antioxidant enzymes in their body, which are produced in response to exercise. Untrained volunteers have a naturally lower antioxidant capacity. They found two studies conducted in trained athletes that showed a positive response to supplementation with vitamins C , E and pro-vitamin A beta-carotene. In contrast, in untrained volunteers the placebo group out-performed people supplemented with vitamin C, and vitamin E.
Unfortunately, some studies did not measure the baseline nutritional status of the participants. This is important because supplementation with antioxidants to improve the oxidative capacity of the body is only likely to be beneficial if the baseline antioxidant level provided by the diet is low. Athletes from a wide range of different disciplines have been found to be deficient in some nutrients due to high nutrient needs and strict schedules. Deficits have been found for zinc in swimmers, a large range of micronutrients in soccer players, female athletes in general and handball players, vitamin D for athletes, dancers, and elite athletes in a wide range of recent studies. It is difficult to find trends in the data as such, however it seems that low intakes or levels are likely to be found for folic acid and vitamin D, and less so for the antioxidant vitamins such as vitamin C. Correcting nutrient deficiencies should be the focus of nutritional therapy. The supply of extra antioxidants is only likely to be effective when baseline intakes are too low.
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