Antioxidant Supplements: Yes or No?

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It has been proclaimed that antioxidant supplements help prevent cardiovascular disease, slow the deterioration of mental function with age, prevent cancer and even slow or reverse the aging process itself. The most popular antioxidants are vitamin C, vitamin E and beta-carotene.

Beta-carotene was shown to significantly increase the risk of dying from lung cancer and from all causes combined in two large prospective studies back in the 1990s.1,2 A recent randomized, controlled clinical trial examined the impact of taking 500 mg of vitamin C, 400 IU of vitamin E and 15 mg of beta-carotene for nearly 7 years in a group of more than two thousand elderly subjects. A battery of 6 cognitive function tests was performed at the beginning and at the end of 7 years in those taking the supplements and those taking placebos. The researchers observed no benefit in any of the cognitive tests in those taking the antioxidant supplements. The results of this study seriously question any claim that antioxidant supplements can slow the loss of mental function that is all too common in older Americans.3

Vitamin C Supplements Promote Cardiovascular Disease

A study of about 2,000 older women with diabetes examined the impact of taking vitamin C supplements on their risk of dying from cardiovascular disease (CVD). Serum vitamin C levels are often on the low side in people with diabetes, and many have assumed extra vitamin C may be beneficial for those with diabetes. However, in this study it was shown that those who took supplements of vitamin C (300 mg or more per day) were more than twice as likely to die from CVD as those who did not take vitamin C supplements. This same study found no association between vitamin C intake from foods and CVD, nor did it find an increased risk of CVD in women who took vitamin C supplements but did not have diabetes. The results of this study demonstrate that vitamin C supplements promote heart attacks and strokes in postmenopausal women with diabetes.4 Based on this study, at least those with diabetes should be discouraged from taking vitamin C supplements.

Vitamin E Increases All-Cause Mortality

The most popular of all the antioxidant supplements in the United States today is vitamin E. This is despite growing evidence that it has little or no benefit and clear evidence that it may promote hemorrhagic strokes and also interferes with the beneficial effects of statins and niacin to slow the progression of atherosclerosis. Despite this, an estimated 22% of Americans 55 years and older are taking supplements of vitamin E in the hopes that it will prevent cardiovascular disease and help them live longer. A large meta-analysis of 19 of the best-controlled studies on vitamin E supplements in people 47 to 84 years of age found no evidence that vitamin E supplements were beneficial.5 Indeed, the results of this analysis of 19 clinical trials with more than 135,000 subjects found that there was a small increased risk of dying from all causes combined in those who took vitamin E supplements. Nine of the 11 clinical trials that used 400 IU or more of vitamin E found an increased risk of dying. The study found an overall increased risk of dying with vitamin E supplements containing 150 IU or more.

Bottom Line:

The belief that antioxidant supplements can improve the health and longevity of most Americans has now been largely discredited. This does not mean that supplements of antioxidants should always be avoided. However, unless there is good-quality scientific evidence as to who would likely get more benefit than harm from taking antioxidant supplements, the best course is to encourage all people to get plenty of natural antioxidants simply by eating plenty of whole foods such as fruits, vegetables, whole grains and beans. Refined grains, sugars, fats and oils have all or most of their beneficial phytochemicals (many with antioxidant effects more potent than vitamins C and E) removed.

 

By James Kenney, PhD, RD, LD, FACN.

References:

1. N Engl J Med 1994;330:1029-35

2. N Engl J Med 1996;334:1150-5

3. Neurology 2004;63:1705-7

4. Am J Clin Nutr 2004;80:1194-200

5. Ann Intern Med 2005;142:00-0000

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