Are Too Many Vitamins Bad for Your Health?

ByABC News
February 27, 2007, 11:35 AM

Feb. 27, 2007 — -- We tend to think of vitamins as healthy. But can you have too much of a good thing?

New research suggests this may be the case when it comes to supplements.

In a meta-analysis study published in the Journal of the American Medical Association, researchers reviewed 68 studies involving more than 200,000 patients to determine whether taking high-dose vitamin supplements -- in particular, beta carotene, vitamin A, vitamin C, vitamin E and selenium -- affected your risk of dying.

What they found was that some of these supplements actually increased risk of death by a small, but significant, amount.

Taking large doses of vitamin A increased the risk of death by 16 percent. Smaller increases were seen for vitamin E (4 percent) and beta carotene (7 percent).

Vitamin C and selenium did not appear to affect the risk of dying.

But exactly how the high doses of supplements affect the risk of death is not clear. The study authors speculate that perhaps the vitamins interfere with the body's defense mechanisms.

The researchers arrived at their conclusions by pooling the results from many different, previously published studies.

Because each of the studies involved in this meta-analysis was very different, though, it is hard to generalize the findings to one particular person, such as you or a family member.

Dr. Meir Stampfer, professor of nutrition and epidemiology at the Harvard School of Public Health, states, "The effects might well differ according to particular characteristics of the population, such as enhanced risk among smokers for beta carotene, but no increased risk among nonsmokers."

Select people should still take supplements. For instance, people who have had gastric bypass surgery need large amounts of vitamin A, says internist Dr. Tina Dobsevage, assistant clinical professor of medicine at Mount Sinai School of Medicine.

She says she also prescribes vitamins D and B12 to patients who have low blood levels of these nutrients.