Vitamin E does not prevent heart attacks and cancer and can actually be harmful when taken in large doses, a top medical journal reported Tuesday. In a seven-year study of thousands of patients with heart disease and diabetes, researchers found that not only did vitamin E supplements fail to prevent heart attacks and cancer, but that they may actually increase the risk of heart failure.
"In conjunction with its lack of efficacy, the potential for harm suggested by our findings strongly supports the view that vitamin E supplements should not be used in patients with vascular disease or diabetes," wrote lead researcher Dr Eva Lonn of the Population Health Research Institute at McMaster University in Hamilton, Canada.
The study was published in the Journal of the American Medical Association (JAMA). It involved 9,541 patients over the age of 55 at 267 study centers in North America and Europe.
All patients had vascular disease or diabetes and were given either a placebo or a daily dose of 400 IU of natural source vitamin E. The initial study ran for just over five years. It was extended for a further two years during which time 3,994 patients continued the study and 730 agreed to passive follow-up.
Earlier studies in epidemiology and experimental biology had suggested that antioxidants such as vitamin E could prevent cell damage and the development of cancerous cells. It had also suggested that antioxidants could reduce the build-up of cholesterol in arterial walls.
"This report effectively closes the door on the prospect of a major protective effect of long-term exposure to this supplement," wrote Dr B. Greg Brown and Dr John Crowley in an accompanying editorial.
They added that this study further shows that the antioxidant craze of the 1990s - when it became popular to use vitamin E, C, and beta carotene supplements in the hopes of warding off cancer and heart attacks - does not actually offer people any real benefits.