Exercise and Antioxidants

In recent years, antioxidants have received positive attention with regards to anti-aging. Furthermore, there is positive evidence that they provide protection against various disease states such as cataracts, diabetes and many cancers. Due to the possibility of enhancement of performance, recovery and protection against free radicals, antioxidants have received much attention in the sports world.

Free radicals are chemical species with one or more unpaired electrons in their outer orbit that makes them highly reactive. Physical activity produces an increase in oxygen consumption reflecting the muscle’s use of oxygen to provide energy in the form of ATP (adenosine triphosphate). As oxygen use increases so does the production of free radicals. There is concern that the increase in free radicals generated during strenuous exercise may exceed the body’s antioxidant defense system, and therefore athletes should take antioxidant supplements.

This is an interesting concept, because it has been found that on the one hand, regular physical exercise enhances the antioxidant defense system and protects against exercise induced free radical damage. However, the level of intensity and duration also requires attention: Intense exercise, particularly in untrained individuals, overrides the defense system, resulting in increased free radical damage. Furthermore, endurance exercise increases oxygen utilization up to 20 times as much as the resting state. Increased oxygen utilization means an increase in the generation of free radicals, with the concerned result of muscles and tissues damage.

Antioxidant supplementation was once perceived as being harmless. However, there is increasing evidence of interactions and potential toxicity. For example, vitamin C and beta-carotene are considered antioxidants at normal concentrations, but at higher concentrations they become harmful substances called prooxidants.

Degree of conditioning of the athlete, intensity of exercise, and diet are thus among the factors determining the extent of exercise induced free radical damage. This article focuses on how effectively can athletes defend against the increased free radicals resulting from exercise and whether antioxidant supplementation is necessary.

In general, the role of overall antioxidant supplementation in a well-nourished athlete is controversial. It is not possible to directly measure free radicals in the body. Most studies measure the by-products that result from free radical reactions because if the generation of free radicals exceeds the antioxidant defenses then more of the by-products will be evident. The results of many studies are conflicting.

Other than vitamin C, E, which positively shows protection against exercise induced oxidative damage, there is no clear scientific evidence that most antioxidant supplements aid in defense against exercise induced oxidative damage. Vitamin E also demonstrated enhanced recovery following intense exercise.>

Athletes adapting to high altitude training (such as skiing or mountaineering), vitamin E might be a beneficial supplement because it did demonstrate less free radical damage and decline in anaerobic threshold in one particular placebo-controlled study on mountaineers.


Antioxidant supplementation is sure to remain a debatable issue because of its hint at performance and health-enhancing roles. However, taking chemicals without a complete understanding of all of their effects may disrupt balance in our bodies. Until more definitive research data is available, the following are recommendations for those athletes considering supplementation:

  • Your diet is also capable of providing the necessary components for an inherent antioxidant system. Eating 5 servings of fruit or vegetables per day along with a balanced exercise program will ensure this.
  • Weekend warriors should strongly consider a more balanced approach to exercise. Failing that, consider supplementation but be aware that very little is known about the long term consequences of antioxidant supplementation.
  • For extremely demanding races (such as an endurance events), or when adapting to high altitude, consider taking a vitamin E supplement (100 to 200 IU, approximately 10 times the RDA) per day for several weeks up to and following the race.
  • Continuously research FDA recommendations, but be wary of advertising and media hype.
  • Remember that other than exercise-induced, free radicals can also be generated from smog and other environmental sources. Do not exercise in areas with significant air pollution.


Herbert, V. Viewpoint: Does mega-C do more good than harm, or more harm than good? Nutr. Today, Jan/Feb: 28-32, 1993