Physicians have been warning for years that vitamin and mineral pills are not only useless for most Americans but potentially hazardous. Megadoses of a number of vitamins commonly included in multivitamins, for example, can be toxic, even life-threatening.

But do many Americans actually take hazardous doses of vitamins?Apparently not, according to a survey of U.S. vitamin use by the National Cancer Institute.

Working from 1987 data on 22,080 adults, the researchers calculated that 51 percent had taken vitamin pills in the past year but that "few, if any, individuals were consuming nutrients in amounts considered toxic."

"Although vitamin and mineral supplementation is a common health habit," the researchers concluded, "it appears not to pose a significant health risk for most of the population."