Loading up on vitamins has been a constant source of controversy, with several studies suggesting that high doses of antioxidant supplements may cause more harm than good.

Vitamin E Danger

A Johns Hopkins University analysis of 19 previous studies found that vitamin E supplements are linked to an increased risk of death—and the higher the dose, the greater the risk.

After reviewing data on 136,000 patients, researchers say that the risk starts when taking daily doses of 150 international units (IU); at 400 IU daily, the risk of dying from any cause is approximately 10% higher than the risk for people who don't take these vitamin pills.

"People take significant amounts of vitamin E because they have a perception that it will provide some health benefit, and that this will help them live longer," says study author Dr. Edgar R. Miller, an associate professor of medicine. "But just the opposite could be the case."

The typical vitamin E intake through diet is approximately 10 IU, and multivitamin pills usually contain 30 to 60 IU of vitamin E.

Most experts continue to stress the importance of eating a diet that is rich in antioxidant vitamins-E, C and beta-carotene—because these foods also contain certain disease-fighting phytochemicals that are not found in vitamin pills.

Miller's study is another blow to the once-popular concept that extra doses of these antioxidants in supplement form would protect the body from dangerous free radicals that can cause cancer, heart disease and other conditions. In fact, this is just one of several studies that have shown the opposite effect.

The vitamin-supplement industry has attacked the methodology of Miller's research, charging that most patients involved in those studies had already been sick when they began vitamin E supplementation.

Beta-Carotene Concerns

Vitamin E is not the only antioxidant supplement that has come under increased scrutiny.

A previous study found that smokers who took high doses of beta-carotene had a higher risk of lung cancer and death compared with those who took a placebo.

Another study discovered that a higher risk of heart disease and cancer continued for years after women discontinued their use of beta-carotene supplements. For men, that increased risk disappeared shortly after stopping supplementation.

This may be because both beta-carotene and vitamin E are fat-soluble, allowing any excess to accumulate in fat-cell membranes. This could explain the adverse effects of betacarotene in women, who, on average, have a higher percentage of body fat than men.

However, another antioxidant nutrient—vitamin C—is water-soluble, and excess amounts are eliminated from the body via urine.

High doses of vitamin C, while not fulfilling the claims of its advocates, have not been shown to be dangerous.

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