Do multivitamins work?

Multivitamins and their effect on atherosclerosis
There is no doubt that, in the test tube, antioxidants such as vitamins E and C, the vitamin A precursor beta-carotene, and the mineral selenium can reduce the free-radical damage that plays a role in the development of atherosclerosis. The B vitamins also have been presumed to have a protective effect because they are an important factor in lowering the levels of homocysteine in the blood, an independent cardiovascular disease risk factor. As we have already seen, studies of human populations have shown that higher concentrations of homocysteine are associated with an increased risk of heart disease. And many researchers have noted that populations with a low dietary intake of antioxidant vitamins show greater progression of atherosclerosis. Such observations, however, cannot prove cause and effect. People who have low antioxidant intake probably have numerous other lifestyle differences as well.

Proving cause and effect requires randomized controlled trials in which supplements are given to one group, and a placebo to another. So far, as we have seen, such clinical trials have not shown a major protective effect in terms of preventing the symptoms of heart disease. But there is always the lingering possibility that the trials have not been long enough.

That is exactly why researchers at Johns Hopkins Hospital in Baltimore decided to investigate whether supplements can slow the process leading to atherosclerosis, by peeking directly into the human body. These days there are a number of imaging techniques, including angiograms, ultrasound, MRI and CAT scans that can actually document the extent of hardening of the arteries. Dr. Eliseo Guallar and colleagues identified 11 randomized, controlled trials that involved giving patients antioxidant supplements or B vitamins and that monitored the status of their coronary arteries. Two of the antioxidants trials used only vitamin E; three used a combination of vitamin E and C; and the others used various combinations of vitamins E and C, beta-carotene and selenium. Several trials used only the B vitamins. In other words, all of the supplement methodologies that had been promoted to reduce cardiac risk were explored. The results were very disappointing. None of the vitamin combinations reduced the progression of atherosclerosis. Furthermore, the vitamins had no effect on preventing the closure of coronary arteries that had been opened up by balloon angioplasty. Based on the thorough evaluation of these well-controlled studies, the Johns Hopkins researchers conclude that the widespread use of vitamin-mineral supplements to prevent atherosclerosis is not supported by the scientific evidence.

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Excerpted from An Apple a Day: The Myths, Misconceptions and Outright Exaggerations about Diet, Nutrition and the Foods We Eat. Published by HarperCollins Publishers Ltd. Copyright 2007 by Dr. Joe Schwarcz. All rights reserved. Reprinted by permission of HarperCollins Publishers Ltd.