Antioxidant Supplements May Have Limited Value
Protection Against Disease May Be Best Derived From Healthy Diet
Nov. 22, 2004 -- Once widely considered a panacea for protecting against diseases associated with aging, antioxidant supplementation is increasingly under fire. Earlier this month researchers reported that taking vitamin E at high doses may do more harm than good. Now new research suggests that low-dose antioxidant supplementation is of only limited value.
Supplementation with small doses of vitamin E, vitamin C, beta-carotene, selenium, and zinc did appear to lower the risk of cancer in men. But French researchers concluded that the observed benefits could easily be derived from eating a balanced diet that includes fruits and vegetables.
Findings from the large Supplementation With Antioxidant Vitamins and Minerals study are reported in the Nov. 22 issue of the journal Archives of Internal Medicine.
"Supplementation may be effective in men (and not women) because of their lower baseline status of certain antioxidants, especially beta-carotene," researcher Serge Hercberg, MD, PhD, and colleagues write. "The present study reinforces the general recommendations of a lifelong diversified diet that includes an abundance of foods rich in antioxidant nutrients."
Clinical Evidence for Vitamin E
Millions of Americans take vitamin E and other antioxidant nutrients with the belief that they will help them live longer and healthier lives, but the scientific evidence to back up the belief is contradictory.
Recent reviews of studies with vitamin E supplementation in patients with heart disease have not shown vitamin E to be effective in preventing heart attacks. However, observations continue to show that eating fruits, vegetables, and other antioxidant-rich foods, or taking antioxidant supplements can protect against heart disease and certain cancers.
The majority of studies on antioxidants and disease prevention have involved much higher doses of the nutrients than are found in the typical diet. The average U.S. diet, for example, supplies around 10 international units of vitamin E, but disease prevention studies generally involve dosages of 400 IU or higher.
In this study, Hercberg and colleagues investigated whether antioxidant supplementation at levels that more closely mimic the nutrient intake provided by a healthy diet helps prevent cancer or heart disease in middle-aged people.
Roughly 8,000 French women between the ages of 35 and 60, and 5,000 men between the ages of 45 and 60 took part in the study. Participants took either placebo pills or an antioxidant formulation consisting of 120 milligrams of vitamin C, 45 IU of vitamin E, 6 milligrams of beta-carotene, 100 micrograms of selenium, and 20 milligrams of zinc.
After 7.5 years, researchers found no differences between the antioxidant group and the placebo group in terms of heart disease, cancer incidence, or death from all causes. However, when the researchers looked at cancer incidence according to gender, supplementation did appear to protect men but not women from developing cancer. Men were 31% less likely to develop cancer than women.
On average, the men had lower levels of antioxidants in their blood at study entry than did the women, and the researchers conclude that this could explain the difference in protection.
"The ineffectiveness of supplementation in women may be due to their better baseline antioxidant status," they wrote.