One in four American adults, including Areh Howell, take high doses of vitamin E every day.
"I take vitamin E for cardiovascular protection," said Howell.
But a new study suggests the supplements may do more harm than good. Researchers at Johns Hopkins University looked at data from 19 different vitamin E studies and came to a startling conclusion.
"People assigned a high dose of vitamin E supplementation had a higher risk of dying. All caused death. All caused mortality, than those who were assigned a placebo or a sugar pill," said Dr. Edgar Miller, lead researcher at Johns Hopkins University.
The increased risk of death, about five percent, was associated with daily doses of 400 international units or higher. Why those mega-doses may be harmful is unclear but the cause may lie in vitamin E's affect on the body's blood clotting ability.
“Vitamin E does increase bleeding time, and it has been in other smaller trials and in one of the largest trials included in our analysis, an increased risk of hemorrhagic stroke," said Miller.
"I've known that too much of certain vitamins are harmful to you," said Howell, "so I am really not too surprised. I guess, I thought 400 was safe."
On average, people get about 10 IU of vitamin E from their diets, and 30 to 60 IU from a typical multi-vitamin.
The study found no increased risk from those lower dosages, but said more research is needed. The study also recommends the government revise its nutritional guidelines, which currently sets a vitamin E ceiling of 1,000 IU per day.