|
Health Options
Alan Titchenal |
Study warns against high
Last week, a study on the risks of high-dosage vitamin E was published in the Annals of Internal Medicine. It concluded that taking vitamin E at a dose of 400 IUs or greater "may increase all-cause mortality and should be avoided."
doses of vitamin EQuestion: How was this study done?
Answer: This study was based on a summary of 19 studies. The individual results were seemingly contradictory, with some indicating benefit and others showing harm from vitamin E supplementation. Dr. Edgar Miller from the Johns Hopkins School of Medicine and his colleagues combined the data from more than 135,000 study participants. The pattern that emerged was a greater number of deaths in the people taking higher doses of vitamin E.
The researchers considered 400 IUs to be the cutoff for high-dose vitamin E but indicated that their analysis showed that mortality risk started to increase at doses above 150 IUs per day.
Q: Does this study have any significant limitations?
A: Virtually all studies have limitations. This type of meta-analysis study evaluates the data from a mixed bag of studies in hopes that the combined data provide a broader perspective. But many of the studies were conducted on people with health problems. Several were conducted with those at high risk of cardiovascular disease. Others focused on smokers or those with health problems such as Alzheimer's disease, Parkinson's disease and age-related vision loss.
Consequently, many of the subjects were likely being treated with various pharmaceutical drugs, which in combination with high-dose vitamin E could produce effects entirely different than those in a healthy person not taking drugs.
This study does raise the flag of caution, indicating that adequate intake of vitamin E is likely preferable to high-dose intake.
Q: If you have been taking high doses of vitamin E, should you be concerned?
A: This study indicates that if you are being treated for specific health problems, you should discuss your supplement use with your physician. If you are taking vitamin E supplements for preventive reasons, it might be wise to limit your intake to 100 IUs per day until more is known about ingesting large doses.
Q: What are good food sources of vitamin E?
A: Since vitamin E is a fat-soluble vitamin, its richest sources are foods such as nuts, seeds and vegetable oils. Some green vegetables, such as spinach and broccoli, and fruits such as mangos and papayas also contribute significant amounts.
See the Columnists section for some past articles.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S. are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, UH-Manoa. Dr. Dobbs also works with the University Health Services and prepares the nutritional analyses marked with an asterisk in this section.