Large doses of vitamin E - widely touted as an elixir of youth - do not protect against heart attacks and cancer and might actually raise the risk of heart failure in people with diabetes or clogged arteries, a study found.
The study, published in Wednesday's Journal of the American Medical Association, is just the latest to cast doubt on the safety and effectiveness of vitamin E supplements and other antioxidants.
The study was designed to examine whether vitamin E pills protect against heart attacks and cancer. Echoing other recent findings, it found no benefit against those conditions.
But the heart failure finding was unexpected and should prompt more research to confirm the results, said Dr. Eva Lonn, a McMaster University cardiology professor who led the study.
Lonn said it is unclear how vitamin E pills might be linked with heart failure, but she theorized that high doses might disturb the balance of beneficial, naturally occurring antioxidants.
Vitamin E has been touted in recent decades as a powerful weapon against aging, capable of protecting against everything from wrinkles to cancer and dementia. Preliminary research over the past 15 years has suggested that antioxidants fight the harmful effects of oxygen, warding off blood-vessel damage and cell abnormalities that can lead to cancer.
About 12 percent of U.S. adults - more than 20 million people - take vitamin E pills containing the same dose used in the study, and about 40 percent - almost 80 million - use supplements containing some amount of vitamin E, according to the industry.
Research released last week on nearly 40,000 healthy women showed no heart benefits from vitamin E pills. And a study reported at an American Heart Association conference in November found that people taking high doses were 10 percent more likely to die of any cause than those taking smaller amounts.
The JAMA study involved 7,030 patients with diabetes or cardiovascular disease other than heart failure.
Patients 55 and older who took about 400 milligrams of vitamin E every day for about seven years on average were 13 percent more likely to develop heart failure than those on dummy pills. Heart failure was diagnosed in 641 vitamin E patients, compared with 578 patients in the placebo group.
The dosage was typical of vitamin E pills widely available at health food stores and pharmacies but well above the recommended 15 milligrams daily for adults, which can be obtained from food.
Lonn said the findings pertain only to vitamin pills, not a diet containing vitamin E-rich foods, including nuts and leafy green vegetables.
"I don't think our study rules out in any way that a balanced diet rich in antioxidants would actually be beneficial," she said.
The study "effectively closes the door" on the theory that high doses have a major protective effect against cancer and narrowing of the arteries, University of Washington health specialists Dr. B. Greg Brown and John Crowley said in an editorial.
The study found no differences in the incidence of or deaths from breast, colon, prostate, oral and gastrointestinal cancer. The researchers said a slightly lower incidence of lung cancer in vitamin E users was probably only a chance finding.
Annette Dickinson, president of the Council for Responsible Nutrition, a trade group for vitamin supplement makers, said the study is "not the final word on vitamin E." She noted that a large National Cancer Institute study is examining whether vitamin E pills protect against prostate cancer.
By Lindsey Tanner