Hoping to protect themselves against heart disease, cancer and other ailments, millions of Americans swallow vitamin E supplements daily.

That practice may have been a waste of money and, according to new research, 10% more likely to lead to an early grave for those who take a daily dose of 400 international units, as opposed to those who do not take the supplement.

Vitamin E's popularity has grown as people increasingly supplement their diets with antioxidants in hope of warding off disease. However, new evidence points toward removing the bottle from the medicine cabinet.

At the levels most often taken in hopes of preventing cellular damage, vitamin E pills appear to do more harm than good, Dr. Edgar R. Miller, a Johns Hopkins University researcher, reported at the American Heart Association's annual scientific sessions.

In an evaluation of 19 studies involving nearly 136,000 people in the past decade, Miller found no risk with a dose of 200 units a day or less, but he found significant problems when people took 400 units or more daily. Most people take between 400 and 800 international units, he said.

It is unclear why large amounts of vitamin E may hasten death, and the results of this study may not be easily translated to young, healthy people because the majority of those in the trials were at least 60 and had pre-existing conditions such as heart disease.

Vitamin E is found naturally in vegetable oils, nuts (particularly almonds) and green, leafy vegetables. It also is common in breakfast cereals.

National guidelines say that 22.5 units from regular dietary intake is an adequate amount for most people. The Institute of Medicine guidelines, which do not recommend supplements, set the maximum safe amount at 1,500 units.

Several experts have suggested that that number needs to be lowered.

While the cardiology community is aware of the risks, "Word hasn't seemed to seep out to the U.S. public, who are still taking vitamin E," said Dr. Robert Eckel, president-elect of the American Heart Association.

In a news release, the trade group Council for Responsible Nutrition questioned the findings. It said the science was not strong and recommended that no changes be made to guidelines on maximum daily levels of vitamin E.