Many vulnerable people who are at risk for heart disease, and even those who are not at risk, routinely take antioxidants to ward off heart attacks and other cardiovascular problems. Alternative medicine practitioners and vitamin companies advise people to take antioxidants, such as vitamin A, vitamin E, and vitamin C, both as a preventative nutrient as well as a treatment after heart disease has been diagnosed. The disease-fighting hypothesis is based on the fact that oxidized low-density lipoprotein (LDL, a.k.a. "bad cholesterol") is taken up by the arteries, leading to plaque formation. The underlying belief behind the supplement regimens is that antioxidants can prevent such oxidation. Theoretically, this makes sense but has yet to be proven clinically.
Some animal studies have demonstrated improved cardiovascular health, leading to large cohort studies, also lending support to this hypothesis. One cohort study, the Lipid Research Clinics' Primary Prevention Trial, demonstrated that men with high vitamin A concentrations in their blood experienced a 36% reduction in their risk for cardiovascular disease. In two studies done in 1993 and published in the New England Journal of Medicine, men and women with high vitamin E intakes also experienced a reduction in risk associated with cardiovascular disease. These two studies became widely quoted and well known around the world. Magazines, newspapers, the vitamin industry, and many websites spread the information like wildfire.
However, medical claims should never be based on population studies but rather on randomized trials, which have thus far failed to confirm any strong correlation between antioxidants and treatment or prevention of cardiovascular disease. Population studies are a good starting point for detecting possible relationships, but the hypothesized relationships must hold up under the high standards put forth by scientific methodology. Although randomized trials have not supported the hypothesis in this case, it does not necessarily mean that there is absolutely no benefit in taking antioxidants as a treatment for heart disease. More comprehensive studies need to be done, however, before medical professionals sanction antioxidants as a cure. As for prevention, obtaining antioxidants as part of a varied diet may be more helpful.
A new report in the Lancet this week suggests antioxidant supplements may be useless and at high doses possibly even dangerous.
The Lancet study examined fifteen randomized trials, each with at least 1,000 subjects who already suffered from some degree of cardiovascular disease or were at high risk of developing it. Results suggested that vitamin A supplements in the form of beta carotene actually increased the rate of death from cardiovascular disease by 0.3% and that vitamin E did not significantly lower cardiovascular death rates. Vitamin C was not included in this study. These results come as a shock to some people who have been touting vitamin E and vitamin A as miracle workers for some years now. Many of the trials included in this examination are well known within the medical community, but these studies taken individually have done little to convince consumers that there are no benefits to taking antioxidants to prevent heart attacks. Hopefully, when looked at as a whole, the studies will make more of an impression.
Just as population studies should not be taken as infallible, the Lancet study should not be taken as the final word. The study examined research using only synthetic vitamins (supplements); results using natural forms of the antioxidants, such as those in food, may show different results. In addition to the actual vitamins, food contains other nutrients that work synergistically. Lifestyle factors, such as exercise and stress levels, were also not accounted for in this study, though they often play a role in disease development a future study, for instance, may examine the possibility that cigarette smoke destabilizes vitamin A, in turn leading to abnormal growths and tumors. Many of the subjects in the Lancet study were indeed smokers. Another complicating factor in the current study that should be taken into account in future ones is the power of high doses of vitamin E to reduce the efficacy of statin drugs often given to patients with high cholesterol.
There is still much that is left unknown even with our new insights. Very high doses of vitamin E were given in the study, and it is possible that lower doses would prove beneficial. In addition, it is possible that antioxidants are more effective in preventing heart disease than treating it, or that they are effective in halting the early stages of heart disease. The studies that were examined in the Lancet looked at patients who already had heart disease, whereas the earlier population studies looked at healthy adults to see if they would develop the disease.
As the American Dietetic Association states, "food and nutrition misinformation can have harmful effects on the health and economic status of consumers." Many Americans may be taking very high doses of antioxidants in the belief that it will save their lives, when in reality it may harm them. The routine use of vitamin E is not supported by research and should not be practiced by patients. Eating a varied diet, exercising, and not smoking are well-established guidelines for a healthy and long life. Instead of a magic pill, people should think about their overall diet and physical activity.
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| Responses:
June 18, 2003 It's unfortunate that the title of your article was not "A Cure for Heart Disease? Not SYNTHETIC Antioxidants, It Seems." However, as your article states, "The study examined research using only synthetic vitamins (supplements); results using natural forms of the antioxidants, such as those in food, may show different results." There are many fine and efficacious natural food supplements on the market and this article appears to impugn all of them. Unfortunately, as with most issues such as this, vested interests are often at play. What about the high level of antioxidants of many French people? As written, this article contradicts the decades of consistent "heart healthy" reports from France. Dan Feldt, MS, MPH |
