In the competitive world of sports, the smallest advantage can make an enormous difference in the outcome of a contest. A supplement that could improve an athlete's strength, speed, or endurance could make the difference between tenth place and first place in a race. Supplements advocated for these purposes are discussed in the article Sports and Fitness Support: Enhancing Performance.

Supplements could conceivably play another helpful role for athletes: aiding recovery from the “side effects” of intense exercise. While exercise of moderate intensity is almost undoubtedly a purely positive activity, high-intensity endurance exercise, such as running marathons, can cause respiratory infections. In addition, all forms of exercise, when carried to the extremes, can cause severe muscle soreness, which may in turn get in the way of training. Herbs and supplements advocated for these problems are the subject of this article.

For information on natural treatments intended to aid recovery from injuries caused by sports, see the Sports Injury article.

Extremely intense exercise, such as training for and running in a marathon, is known to lower immunity, and endurance athletes frequently get sick after maximal exertion. Vitamin C might help prevent this, although not all studies agree.

According to a double-blind, placebo-controlled study involving 92 runners, taking 600 mg of vitamin Cfor 21 days prior to a race made a significant difference in the incidence of sickness afterwards.1 Within 2 weeks after the race, 68% of the runners taking placebo developed symptoms of a common cold, versus only 33% of those taking the vitamin C supplement. As part of the same study, nonrunners of similar age and gender to those running were also given vitamin C or placebo. Interestingly, for this group, the supplement had no apparent effect on the incidence of upper respiratory infections. Vitamin C seemed to be specifically effective in this capacity for those who exercised intensively.

Two other studies found that vitamin C could reduce the number of colds experienced by groups of people involved in rigorous exercise in extremely cold environments.2 One study involved 139 children attending a skiing camp in the Swiss Alps, while the other enrolled 56 military men engaged in a training exercise in Northern Canada during the winter months. In both cases, the participants took either 1 g of vitamin C or placebo daily at the time their training program began. Cold symptoms were monitored for 1 to 2 weeks following training, and significant differences in favor of vitamin C were found.

However, one very large study of 674 US Marine recruits in basic training found no such benefit.2 The results showed no difference in the number of colds between the treatment and placebo groups.

What’s the explanation for this discrepancy? There are many possibilities. Perhaps basic training in the Marines is significantly different from the other forms of exercise studied. Another point to consider is that the Marines didn’t start taking vitamin C right at the beginning of training, but waited 3 weeks. The study also lasted a bit longer than the positive studies mentioned above—it continued for 2 months. Maybe vitamin C is more effective at preventing colds in the short term. Of course, another possibility is that it doesn’t really work. More research is needed to know for sure.

For more information, including dosage and safety issues, see the full Vitamin C article.