Antioxidants and Heart Disease

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The use of high-dose antioxidant supplements, such as vitamins E and C, and others like selenium and beta-carotene, have been widely touted in the popular press as being useful for treating and preventing heart disease. In theory, antioxidant supplements were believed to help slow or stop the clogging of arteries by blocking oxidative damage to cholesterol-rich particles believed to contribute to the growth of plaques that clog blood vessels. Preliminary observational research also suggested that people who took in more vitamin E from food and/or supplements were somewhat less likely to die of heart disease.

Recent studies put supplement theory to test

 

However, observational studies, by their very nature, are only suggestive, not conclusive. A correlation between taking antioxidants and better health could be caused by the fact that more health conscious people are more likely to adopt behaviors such as taking vitamin E and other antioxidants because they are being touted as “healthy” by the mass media. This effect is compounded when their doctors and other health professionals also jump on the bandwagon and suggest that such supplements are a good idea. In the last few years, more carefully designed clinical trials have begun to yield more scientifically accurate results. Unfortunately, the results of these placebo-controlled clinical trials with vitamin E and/or other antioxidants have not been encouraging for those who would like to believe such supplements can help prevent heart disease.

 

Angioplasty patients should avoid high-dose vitamins

 

At the Canadian Cardiovascular Conference 2000, Dr. Jean Claude Tardiff of the Montreal Heart Institute reported findings from a placebo-controlled trial of 317 patients who had undergone angioplasty. Those given high doses of antioxidants (Vitamin E -- 700 IU, Vitamin C -- 500 mg, and beta-carotene --30,000 IU) received no benefit. Dr. Tardiff said the antioxidant supplements tended “to make the arteries more fibrotic [increased growth of scar tissue]. High dosage multivitamins... adversely affect plaque composition after angioplasty.” The results of this study certainly mean that patients who have undergone angioplasty to help open clogged coronary arteries should be advised against taking high doses of vitamin E and other antioxidant supplements.

 

High-dose antioxidants found to increase plaque

 

More recently, a study looking at 160 patients, at increased risk of heart disease because of low HDL levels, examined the impact of these four options:

 

1. High-dose antioxidants (vitamins E and C, beta-carotene and selenium)

 

2. High-dose niacin plus a statin drug

 

3. High-dose antioxidants, niacin and the statin drug

 

4. A placebo

 

The good news was that after three years, those taking the combination statin plus high-dose niacin experienced, on average, a regression or shrinkage of the plaques clogging their arteries.

 

However, when this drug combination was taken with the antioxidant supplements, their favorable impact on atherosclerotic plaques was blunted. But overall, patients taking the high-dose niacin and statin combination fared better than those who did not. Much more progression of artery-clogging plaques occurred in all patients not taking the niacin and statin medications, whether or not they took antioxidant supplements.

 

In addition, patients taking the niacin plus statin drug experienced a marked reduction in heart attacks, strokes and other clinical events, but this benefit was reduced in those also taking the antioxidant supplements.1 The results of this study and early work by this same research group suggest that high doses of antioxidants have adverse effects on the level of the major protective component of HDL particles (the “good cholesterol” particles in the blood).

 

The bottom line

 

The results of these and other clinical trials certainly cast serious doubt on the safety and effectiveness of antioxidant supplements for treating and preventing cardiovascular disease.2 The results of clinical trials to date certainly suggest that high-dose antioxidant supplements are neither safe nor effective in treating patients at high risk of cardiovascular disease who are being treated with drugs and/or surgery.

 

Ongoing clinical trials with people at lower risk of cardiovascular disease should help clarify what risks and benefits antioxidant supplements have for the general public. In the meantime, it seems prudent to discourage most people from taking high doses of antioxidant supplements in order to prevent cardiovascular disease. Such supplements have not been proven to be effective in well-controlled studies, and there is even growing reason to question their safety.

 

One should not conclude that high doses of all food supplements are always a bad idea. Niacin, used in this study, is a form of vitamin B-3, and the dosage given is far in excess of the RDI, and yet it is currently the most effective way to raise low levels of HDL. High doses of niacin, either alone or combined with a statin drug, helps prevent heart disease.

At high doses, or “megadoses,” vitamins and other nutrients can act like drugs. This means they should be tested for safety and effectiveness before being prescribed or recommended. But high doses of niacin, like other drugs, even though effective, still require medical monitoring for safety. The popular press is being irresponsible in touting such supplements long before convincing evidence of either safety or effectiveness has been established scientifically. Given the public interest in nutrition, health professionals need to be careful not to jump on the bandwagon for the latest miracle cure before reliable scientific research establishes its safety and efficacy.

 

By Dr. James J. Kenney, PhD, RD, FACN.

 

References:

 

1. N Engl J Med 2001;345:1583-92

 

2. Curr Opin Lipidol 2001;12:49-53

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