Antioxidants, an important compound our bodies use to combat disease, are made up of enzymes as well as vitamins A, C, and E. They protect our bodies against the dangerous effects of free radicals found in many things we can't avoid such as pollution, pesticides, ultra-violet radiation (from the sun) and even our metabolism. When your metabolism is increased with exercise, the production of free radicals rises, as does the need for more antioxidant protection. One doctor in the US, Kenneth Cooper, believes strenuous exercise such as marathon training can increase the risk of cancer because the exertion produces larger amounts of free radicals. He strongly supports the taking of antioxidant supplements to reduce this oxidative damage.

Other compounds under research include coenzyme Q10, L-carnitine, glutamine and branch chain amino acids (BCAA) including leucine, isoleucine and valine. Coenzyme Q10 is like a vitamin and helps convert food and supplements into energy our bodies can use. Since very little of this energy can be stored, coenzyme Q10 is needed to constantly renew the energy supply. The heart muscle is the biggest user of coenzyme Q10 and an adequacy of this compound is important for cardiovascular performance. The supplementation of coenzyme Q10 has been shown to increase angina sufferers' cardiac output and improve their exercise performance. As for well-trained athletes, one study in Spain showed that supplementing coenzyme Q10 actually increased the endurance time and speed of a group of elite male runners on a treadmill.

In the past decade, L-carnitine has been one of the most studied and used supplements. Some of its roles include the functioning of our metabolism, the elimination of waste and aiding our bodies to use fat as an energy source. During long-endurance athletic events, the body primarily uses fat (fatty acids) for energy. Studies have shown that an increase of L-carnitine in a supplement form causes an improvement in endurance. One study also showed an increase in the use of oxygen taken in and a reduction in the muscle soreness that happens between 24 and 48 hours after strenuous exercise by using L-carnitine.

BCAA promote protein synthesis and stop protein breakdown due to exercise. Studies have shown that by taking the acids before and during an endurance event, there was less muscle breakdown. It has even been shown to achieve weight loss in wrestlers who had to undergo very restricted diets in order to reach a competitive weight. Glutamine is the most abundant amino acid in the body and is important for immune functioning. After a tough workout, the level of glutamine is depleted, making you more at risk of infections. When glutamine was given to a group of marathoners following a race, 81 per cent remained free of infection versus only 49 per cent of the group who weren't given any supplement.

Even though research is starting to understand that supplements can lessen the damaging effects of intense exercise, there's still much to learn. Nearly all of these findings have only used short-term research and have mainly focused on subjects who were already deficient in these nutrients. It's not yet clear what the long-term benefits of supplementation are or the increases in performance in athletes who have adequate reserves.

And one other thing, before you go out and buy a load of supplements, remember that food is still the best way of acquiring these nutrients. Antioxidants found naturally in food work in harmony far better than any pill. Too much of one nutrient can be just as harmful as too little.