TUESDAY, July 19, 2005 (HealthDay News) -- Many Americans still take high daily doses of vitamin E despite mounting evidence that the vitamin offers no health benefit and could be dangerous, a new study finds.
The researchers found that just over 11 percent of American adults routinely consume at least 400 IUs of vitamin E on a daily basis. Another 26 percent of American adults take supplements that include lower amounts of the vitamin.
Reporting in the July 19 issue of Annals of Internal Medicine, the authors referred to a range of recent studies that suggested vitamin E supplementation in doses at or exceeding 400 IUs may increase the risk for premature death from chronic illness such as heart disease and cancer.
"Basically, what we're trying to do is let folks know that many Americans are still consuming too much vitamin E, and that too much is really not that good," said study co-author Ali H. Mokdad, of the Chronic Disease Center at the Centers for Disease Control and Prevention in Atlanta.
Vitamin E supplements in the 400 IU range far exceed the current federally recommended dietary allowance (RDA) guideline set to reflect the daily nutritional needs of most healthy men, women and children. The RDA for vitamin E --according to the National Institutes of Health (NIH)-- is 22.5 IUs for adults.
The NIH points out that vitamin E deficiency is rare, noting that the nutrient is found naturally in many food sources such as plant oils (including vegetable oil and margarine), leafy green vegetables, whole grain cereals, liver, egg yolks, milk, nuts, seeds and butter.
Mokdad and his colleagues analyzed vitamin E supplementation data among more than 4,600 white, black and Mexican-American adult men and women who had been included in the 1999-2000 National Health and Nutrition Examination Survey.
All the participants had completed interviews and questionnaires on their daily dietary intake, and all underwent blood tests and neurological, fitness and oral health evaluations.
The researchers found that daily vitamin E intake routines above 400 IUs were similar for men and women, and that such supplementation increased with age -- particularly among white adults over the age of 60.
White adults were also generally more likely to take vitamin E supplements, as were those patients with a history of heart disease, stroke or diabetes.
Those who regularly took vitamin E supplements were also more likely to ingest supplements that included vitamin C and beta-carotene. The researchers suggested that this combination of supplements further added to the potential harmful effects related to the ingesting of high doses of vitamin E.
The authors concluded that high-dosage vitamin E supplementation is common, and that concerns about the practice should be raised by health-care professionals who could advise their patients of potential health risks.
They noted, however, that dangerous supplementation habits are so widespread that doctors themselves are often practicing similar risky supplement routines -- complicating efforts to promote accurate public health information about vitamin E.
Both Mokdad and his colleague, Dr. Umed A. Ajani, said that the exact mechanism by which high-dose vitamin E supplementation poses health risks is not yet fully understood. However, they emphasized, the danger is real.
"We know there is an increased risk, and at this point this affects a sizeable proportion of the U.S. population," Ajani said.
Mokdad suggested that now-discredited research that had been widely publicized more than a decade ago had led many people to erroneously conclude that vitamin E supplementation was beneficial and protective -- and that more was better.
"There was this theory that antioxidants such as vitamin E will lead to less blockage in the arteries," said Mokdad. "But there have been several clinical trials since that show that, in reality, this is not true. Unfortunately there was a lot of media attention given to the antioxidant theory, and it seems people haven't kept up with the most recent data that showed, in fact, that it may harm you a little bit."
Both Mokdad and Ajani agreed that vitamin supplementation overall is ripe for abuse and poorly understood.
"It's not controlled, it's easily available, and it makes people feel good that they're doing something for themselves," Mokdad said. "Unfortunately, it's thought of as an easy solution for a major problem with poor diets. And that's why we're trying to get this public health message out there -- that you need to get out of this mentality that a pill will sort out our problems."
"There may be some supplements out there that are good for people to take now and then," Ajani added. "But in the case of vitamin E, the research does not support any benefit, and in fact it may harm you."
Dr. Jay Brooks, chief of hematology/oncology at the Ochsner Clinic Foundation in New Orleans, concurred.
"Everyone thinks that taking vitamins and supplements is perfectly OK to do," Brooks said. "But these are active drugs, and we don't understand completely what they do. So, I do not recommend to any of my patients to be taking extra dosage of vitamins, unless they're involved in a research study."
"I know of no disease . . . that can be prevented or treated by taking vitamin E," Brooks added. "So, I don't take it personally to prevent prostate cancer or other diseases. We just don't know if it works, and it may actually be detrimental."
For more on vitamin E, check out the The National Institutes of Health's Office of Dietary Supplements.