Patients may have questions about taking antioxidants.
If you take a trip down the vitamin/mineral aisle in a pharmacy or the cereal aisle in the supermarket, you will notice that antioxidants are promoted as necessary for a healthy body. Some products say that they are “high in antioxidants” or that they have “50% more antioxidants.”
Antioxidants are highly promoted by media, some physicians and dietitians, and nutritional industries for a variety of reasons. They are said to help slow the aging process or help prevent vision loss, cancer, heart disease, strokes, and other chronic diseases.
Once it was thought that antioxidants were harmless, but researchers are learning that it might be possible to get too much of a good thing. Very little is known about how much a person should get or about the long-term consequences of gigantic doses of antioxidants.
What Are Free Radicals?
The body generates hundreds of substances called “free radicals” when converting food to energy. Other free radicals are extracted from food or breathed in from the air, and some are generated by the sunlight’s action on the skin and eyes.
Once formed, these toxic compounds can start a chain reaction like dominoes. Cells may function poorly or die. Resulting oxidative stress is associated with more than 200 diseases.
The scavenger free radical molecules are missing an electron in their outer shells and will do anything to fill them, including stealing electrons from your body’s cellular structures. Such cellular thievery may damage DNA, proteins (enzymes), and cell membranes. When these cells are damaged, your body is damaged, creating the foundation for disease and accelerated aging.
What Are Antioxidants?
Antioxidants are molecules which can safely interact with free radicals and terminate the chain reaction before vital molecules are damaged. Although there are several enzyme systems within the body that disarm free radicals, the principal antioxidants are vitamin E, beta-carotene, vitamin C, and selenium.
When these antioxidants neutralize free radicals by donating an electron particle they are left with a small problem. The antioxidants are now missing an electron and have become free radicals themselves. The body cannot manufacture these antioxidants, so they must be supplied in your diet.
Does Research Support Use of Antioxidants?
In theory, antioxidants have the potential to improve or prevent a number of chronic diseases. But using them does not mean that they will resolve your health problems. Research has not offered a lot of support so far for taking vitamin C, vitamin E, or beta-carotene to provide protection against heart disease, cancer, or other chronic conditions.
Several studies showed no difference in major cardiovascular events and cancer when patients took either vitamin E or a placebo. Only 1 study in Israel showed a marked reduction in coronary heart disease among people with type 2 diabetes.
A beta-carotene study showed that the antioxidant provided no protection against heart disease or stroke. A study of vitamin and mineral supplements (vitamin C, vitamin E, beta-carotene, selenium, and zinc) showed no decrease in overall rates of cardiovascular disease.
Unfortunately, few trials have gone on long enough to show a benefit in cancer patients. Several beta-carotene trials have shown no benefit on cancer.3,6
One trial using selenium showed a reduction in cancer risk and all-cause mortality among men but no apparent benefit for women.1
Another selenium trial in patients with skin cancer provided some hope by demonstrating significant reductions in cancer and cancer mortality, including colon, lung, and prostate.9
The one bright spot for antioxidant vitamins is a trial where patients taking vitamin C, beta-carotene, and zinc received some protection from antioxidants against the development of advanced age-related macular degeneration, but not cataracts.
The Bottom Line
To date, randomized, placebo-controlled trials are at best inconclusive but generally don’t provide strong evidence that antioxidant supplements have a substantial impact on diseases such as cardiovascular events and cancer. But antioxidants continue to be added to breakfast cereals, energy bars, sodas, sports drinks, and other processed foods. Often claims have stretched and distorted data. It appears that antioxidants aren’t the magical solution they are sometimes hyped to be.
Mr. Brown is professor emeritus of clinical pharmacy and a clinical pharmacist at Purdue University College of Pharmacy, Nursing, and Health Sciences, Department of Pharmacy Practice, in West Lafayette, Indiana.
The Nutrition Source. Antioxidants: beyond the hype. Harvard School of Public Health website. www.hsph.harvard.edu/nutritionsource/what-should-you-eat/antioxidants/. Accessed June 3, 2012.
Lee IM, Cook NR, Gaziano JM, et al. Vitamin E in the primary prevention of cardiovascular disease and cancer: the Women’s Health Study: a randomized controlled trial. JAMA. 2005;294:56-65.
Lonn E, Bosch J, Yusuf S, et al. Effects of long-term vitamin E supplementation on cardiovascular events and cancer: a randomized controlled trial. JAMA. 2005;293:1338-1347.
Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto miocardico. Lancet. 1999;354:447-455.
Milman U, Blum S, Shapira C, et al. Vitamin E supplementation reduces cardiovascular events in a subgroup of middle-aged individuals with both type 2 diabetes mellitus and the haptoglobin 2-2 genotype: a prospective double-blinded clinical trial. Arterioscler Thromb Vasc Biol. 2007:ATVBAHA.107.153965.
Hennekens CH, Buring JE, Manson JE, et al. Lack of effect of long-term supplementation with beta-carotene on the incidence of malignant neoplasms and cardiovascular disease. N Engl J Med. 1996;334:1145-1149.
Hercberg S, Galan P, Preziosi P, et al. The SU.VI.MAX Study: a randomized, placebo-controlled trial of the health effects of antioxidant vitamins and minerals. Arch Intern Med. 2004;164:2335-2342.
Cook NR, Albert CM, Gaziano JM, et al. A randomized factorial trial of vitamins C and E and beta-carotene in the secondary prevention of cardiovascular events in women: results from the Women’s Antioxidant Cardiovascular Study. Arch Intern Med. 2007;167:1610-1618.
Duffield-Lillico AJ, Reid ME, Turnbull BW, et al. Baseline characteristics and the effect of selenium supplementation on cancer incidence in a randomized clinical trial: a summary report of the nutritional prevention of cancer trial. Cancer Epidemiol Biomarkers Prev. 2002;11:630-639.
A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta-carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8. Arch Ophthalmol. 2001;119:1417-1436.
A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E and beta-carotene for age-related cataract and vision loss: AREDS report no. 9. Arch Ophthalmol. 2001;119:1439-1452.