Report Warns Against Taking Large Vitamin Doses for Prevention
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However, food should be a sufficient source of antioxidants, says the report. Those who take supplements may wonder whether certain types or forms are preferable. "It doesn't have any impact on the upper limit, but if you are going to take a supplement, it really should be taken with a meal [to be better absorbed]," says panelist Maret Traber, PhD, a nutritionist at Oregon State University.
For vitamin C, the daily recommendation is 75 mg for women and 90 mg for men. These numbers actually represent a 50% increase for men and a 25% jump for women. Smokers should get another 35 mg of C daily, as the antioxidant may counter the damage smoking does to cells, according to the report. The suggested upper limit, however, is 2,000 mg daily of vitamin C for adults. Fruits and vegetables are a good source of C.
With vitamin E, the guidance is 15 mg of the substance daily, and it can be most efficiently obtained from foods containing alpha-tocopherol such as nuts, seeds, liver, and leafy green vegetables. This is a 100% increase over the previous level. The suggested upper limit for vitamin E is 1,000 mg per day.
The recommendation for selenium is 55 micrograms per day in foods like seafood or liver. The safe upper limit is 400 micrograms daily. Suggested levels for beta-carotenes and carotenoids, found in many plants, weren't included in the report, because the authors say there's doubt the nutrients actually are antioxidants.
Doubts or not, many people are taking supplements, and not necessarily with their doctor's knowledge or advice -- even for serious conditions like heart disease. Many are taking "huge doses of vitamin E," says Ernst Schaefer, MD, a professor of medicine and nutrition at New England Medical Center and Tufts University.
"All I can do to my patients is to say, 'Look, I'm data driven. I'm not saying that these things don't help you, but in fact we have to be guided by [research],'" Schaefer tells WebMD.
The IOM report also focuses on the need for more research to determine whether antioxidants really work. Meanwhile, the report is being generally well received.