Approximately 30 percent of Americans take an antioxidant supplement daily, likely due to their reputation for preventing cancer and increasing longevity. While antioxidant intake has been widely believed to increase longevity due to their role in stabilizing free radical damage associated with aging, scientific evidence has failed to prove that antioxidants directly increase longevity. Further, antioxidant supplements may not be effective in cancer prevention like the antioxidants obtained from fruits and vegetables and may actually be harmful.
Antioxidants Stablize Free Radicals
Antioxidants play a role in the pathophysiology of cancer. They help prevent the free radical damage that is associated with cancer by stabilizing free radicals. Common dietary antioxidants that are also available in supplement form include beta-carotene; selenium; and vitamins C, E and A. Although antioxidants play a role in cancer, the American Dietetic Association does not recommend supplemental antioxidants for cancer prevention.
Antioxidant Supplementation May Increase Mortality
The Beta-Carotene and Retinol Efficacy Trial, or simply CARET, was a large double-blind clinical trial in which participants who were smokers, former smokers or exposed to asbestos were randomly assigned to take a beta-carotene and vitamin A supplement or a placebo. After a median follow-up of four years, lung cancer incidence was 28 percent higher and all-cause mortality rate was significantly higher in participants who took beta-carotene supplements. The CARET study was halted early due to significant increases in cancer incidence and mortality.
Obtain Antioxidants From Food Sources
A panel of renowned scientists performed a major review of peer-reviewed literature that is published in the World Cancer Research Fund and American Cancer Research Institute Policy Report on Food, Nutrition and Physical Activity. They found that fruit and non-starchy vegetables are protective against some cancers possibly due to the other bioactive components they contain. Bioactive food components are nonessential molecules capable of modulating metabolic processes. Bioactive food components likely act together and not in isolation in modulating processes. This may explain why antioxidant supplementation has not been shown to be as effective in cancer protection as fruit and vegetables.
Aim for More Fruits and Vegetables
No states in the U.S. reach the Healthy People 2010 national objective for fruit and vegetable consumption. People should consume at least five daily servings of fruits and vegetables to reach antioxidant recommendations as opposed to vitamin supplementation. Antioxidant supplements should not be recommended as a preventive measure for cancer, especially in high-risk groups, such as smokers. While antioxidants from fruit and vegetables protect against cancer, no clear link between antioxidant intake and longevity has been established.
References
- "Annals of Internal Medicine"; The Prevalence of High Intake of Vitamin E From Use of Supplements Among U.S. Adults; E.S. Ford, et al.; July 2005
- "American Journal of Epidemiology"; Fruit, Vegetable and Antioxidant Intake and All-Cause Cancer and Cardiovascular Disease Mortality in a Community-Dwelling Population in Washington County; J.M. Genkinger, et al.; December 2004
- "Morbidity and Mortality Weekly Review"; Fruits and Vegetable Consumption Among Adults, United States, 2005; March 2007
- "Nutrition Review"; The Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study in Finland; J. Blumberg, et al.; July 1994
- "Journal of the American Dietetic Association"; Vegetables, Fruit and Cancer Prevention: A Review; K.A. Steinmetz, et al.; October 1996
- "American Journal of Clinical Nutrition"; Increased Green and Yellow Vegetable Intake and Lowered Cancer Deaths in an Elderly Population; G.A. Colditz, et al.; January 1985
