Antioxidants

Contributed By: Dick Raford, MD from cyclingforums


Over the last few years, we have been hearing more and more about antioxidants - vitamins (C, E, and beta carotene) that neutralize dangerous compounds known as free radicals. Although the focus of much of the discussion has been on cardiovascular health, there has been a suggestion that free radicals may contribute to a slow recovery after tough rides.

What is a free radical? It is a molecule with an unpaired electron, and a normal by product of all biologic systems (exercising or not). These free radicals are unstable and can produce cellular damage such as lipid peroxidation (damage of lipid membranes) and changes in membrane protein structure - both of which have been suggested as possible culprits in the development of heart disease and cancer. An antioxidant, as the name suggests, can neutralize free radicals before they interact with living tissue, detoxifying them into water and oxygen.

A review of studies on the role of anti-oxidants in exercise suggests that although exercise does increase the rate of lipid peroxidation (the formation of free radicals), there is also a rise in the natural antioxidant activity in the blood. And with regular training, the antioxidant defense system increases even further. There is little data as to which has the upper hand in this balancing act - the free radicals or the defenses. There has been speculation that the "weekend warriors" who do not have a regular training program, might be more susceptible to free radical damage. However, there is no convincing evidence that supplements of antioxidants are of any value in counteracting the potential effects of free radicals, for either competitive cyclists or recreational exercisers.

One study suggested that the use of antioxidants in the form of vitamins C, E, and beta carotene decreased muscle damage in a group of runners as compared to a control group, and there are numerous anecdotal reports that vitamin C taken before a ride diminished the amount of muscle soreness the next day. The only controlled studies were with 600 IU of vit E for 2 days before exercise (no effect) and a second with 3 grams of vit C per day for 3 days before and 4 days after an exercise bout (reduced soreness). However, none have suggested a positive effect of any of the antioxidant vitamins on actual exercise performance or the rate of postexercise recovery in athletes on a balanced diet.

There is considerable speculation on the long term benefits of antioxidants in general. A study of nurses and male professionals published in 1993 demonstrated a lower rate of heart disease in those taking Vit E supplements. And a study from China indicated that the use of a multivitamin, containing antioxidants among other things, lowered the cancer death rate by 13%. However a more recent study (1996) indicated the opposite, that patients at risk for lung cancer had a HIGHER cancer rate if they took beta carotene supplements, and the study was terminated early because of those results.

How about antioxidants in cardiovascular disease - an area where there has been considerable interest and research? The most recent study demonstrated no benefit of antioxidants over placebo in blunting the effect of atherosclerosis, and indeed even suggested some harm in that antioxidants appeared to blunt the effectiveness of a proven therapy (simvastatin-niacin). As an aside, there has been interest in the benefits of other vitamins (B vitamins and folate) in the treatment of coronary artery disease - via their effect on homocysteine metabolism. The evidence is strong enough that one of my cardiology partners routinely puts his post angioplasty patients on a multivitamin plus an additional 400 mcg of folic acid and 50 mg of vitamin B6.

The bottom line is that very little evidence to support the short term benefit of antioxidants for the competitive athlete - and plenty of controversy remains as to the long term health benefits. Although there is no evidence that they will do you any harm in the usual doses, megadoses have been reported to have side effects and actually decrease optimum physical performance.

As there is general agreement that the natural sources of these micronutrients appear to be more effective than the vitamins you can buy in a bottle, increasing the fruits and vegetables in your diet might be a good compromise if you feel you'd like to give them a try. And if you opt to go with reasonable doses of vitamin supplements, only your pocketbook would appear to be at risk.

  • Vit C
    • Food sources: citrus fruits, potato, broccoli, cauliflower, cabbage, watermelon, cantaloupe
    • RDA: 60 mg/day - 1 orange, 1/2 cup broccoli
    • Supplement: 250-500 mg/day
    • Warnings: More than 500 mg can cause diarrhea
  • Vit E
    • Food sources: vegetable oil, nuts, wheat germ, margarine, seeds, leafy greens, asparagus
    • RDA: 8-10 mg/day (4-5 oz of peanuts)
    • Supplement: 200-800 IU
    • Warnings: No serious side effects in the doses recommended
  • Vit A
    • Food sources: milk, cheese, egg, liver, fish oil
    • RDA: 800-1000 micrograms
    • Supplement: None; your body will convert B Carotene safely into Vit A
    • Warnings: Toxic (even lethal) at high doses
  • Beta carotene
    • Food sources: carrots, cantaloupe, squash, sweet potato, spinach
    • RDA: None, but 5 - 6 mg are suggested (1/2 carrot)
    • Supplement: 6-15 mg per day
    • Warnings: Not toxic but in high doses your may turn yellow (carotenemia) 

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