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Antioxidants: Antidote to Aging?

antios The secret to lasting youth may not lie in a pill or potion, but in produce! Carrots, spinach, and broccoli—among other vegetables—contain compounds known as antioxidants.

Antioxidants and Free Radicals in the Body

As the body uses oxygen, free radicals—oxygen molecules that are missing electrons—are formed. These free radicals are unstable molecules that can cause damage to cells. This cell damage is thought to build up over time and may lead to aging and disease. Everything from cancer and heart disease to wrinkles and cataracts may be attributed to the action of free radicals. Environmental factors such as exposure to radiation and tobacco smoke may also increase the number of free radicals in the body.

Antioxidants are compounds that work to deactivate free radicals. The best known antioxidants are vitamins A, E, C and beta-carotene, but there are many others, including selenium, lutein, and lycopene.

Research Shows Mixed Results

The ability of antioxidant supplements to prevent disease has not been widely supported by scientific evidence. Some observational studies (which track participants without making changes to their diet or treatments) have found reduced risk of certain diseases with a higher intake of fruits and vegetables that contain antioxidants. However, clinical trials have not shown any benefit.

One exception is the National Eye Institute study of age-related eye disease. It found that a combination of antioxidants and zinc reduced age-related macular degeneration (AMD) by 25% in people who had intermediate or advanced AMD in one eye. The risk was reduced by about 17% when antioxidants were used alone.

Too Much of a Good Thing?

Some studies have suggested that for certain people, over consumption of antioxidants can be harmful. Studies of beta-carotene in humans were stopped in 1994, after results suggested that people at risk for cancer were at even greater risk after taking high doses of synthetic beta-carotene. A 2005 meta-analysis (an analysis of the results of multiple studies) suggests that taking more than 400 IU/day of vitamin E may also be harmful to one's health.

Benefits of Dietary Changes Are Clear

Though the jury is still out on the role of antioxidant supplements as disease and age fighters, consuming more antioxidant-rich fruits and vegetables has well-documented benefits in improving health, aside from their antioxidant contents.

Antioxidant Recommended Amount* Good Food Sources
Vitamin C Women: 75 mg Men: 90 mg Smokers: extra 35 mg Citrus fruits; vegetables such as broccoli, cauliflower, and kale
Vitamin E 15 mg Fortified cereals, vegetable oils, nuts, mangoes, and wheat germ
Selenium 55 micrograms (mcg) Tuna, ham, brown rice, whole wheat bread
Vitamin A Women: 700 REA** Men: 900 REA As retinol: Eggs, liver, vitamin A-fortified milk As beta-carotene: Yellow-orange or dark-green leafy vegetables and fruits, such as kale, beet greens, spinach, carrots, sweet potatoes, pumpkin, papaya, apricots, parsley, and basil
*Recommended amounts are given as dietary reference intakes (DRIs), which replace recommended dietary allowances (RDAs); these are the government's recommendations for good health. **REA = retinol equivalents; a measurement of vitamin A that includes the two major forms of vitamin A found in foods: retinol and beta-carotene. There is no separate DRI set for beta-carotene.

Are Supplements Necessary?

The American Heart Association and the American Cancer Society do not endorse antioxidant supplements for the general population, but they do recommend a diet with plenty of antioxidant-rich fresh fruits, vegetables, and whole grains. You should also discuss any antioxidant use with your doctor before you begin.

  • American Heart Association

    http://www.heart.org/HEARTORG/

  • National Cancer Institute

    http://www.cancer.gov/

  • National Institute on Aging

    http://www.nia.nih.gov/

  • Canadian Cancer Society

    http://www.cancer.ca/

  • Canadian Cardiovascular Society

    http://www.ccs.ca/

  • Antioxidant Supplements for Health: An Introduction. National Center for Complementary and Alternative Medicine website. Available at: http://nccam.nih.gov/health/antioxidants/. Updated May 2010. Accessed July 8, 2010.

  • Calvagna, M. Selenium. EBSCO Health Library website. Available at: http://www.ebscohost.com/healthLibrary/. Updated February 2009. Accessed July 8, 2010.

  • Food and Nutrition Information Center. US Department of Agriculture website. Available at: http://www.usda.gov/. Accessed June 30, 2008.

  • The heart outcomes prevention evaluation study investigators, vitamin E supplementation and cardiovascular events in high-risk women. N Engl J Med. 2000;342:154-160.

  • Luchsinger JA, Mayeux R. Dietary factors and Alzheimer's disease. Lancet Neurol. 2004;3(10):579-87.

  • Meydani M. Nutrition interventions in aging and age-associated disease. Ann N Y Acad Sci. 2001;928:226-235.

  • Miller ER, Pastor-Barriuso R, Dalal D, Riemersma RA, Appel LJ, Guallar E. Meta-analysis: high-dosage vitamin E supplementation may increase all-cause mortality. Ann Intern Med. 2005;142(1):37-46.

  • Stanner SA, Hughes J, Kelly CN, Buttriss J. A review of the epidemiological evidence for the 'antioxidant hypothesis'. Public Health Nutr. 2004;7(3):407-422.