Your parents may still tell you to take your vitamins, but doing so may not reduce your risk of cancer.
A recent study that found calcium and vitamin D supplements do not reduce the odds of developing breast cancer is the latest to deflate the cancer-prevention claims of some vitamin proponents.
A federal science panel last month had concluded there is no evidence for recommending certain vitamin supplements for cancer prevention. Even the Council for Responsible Nutrition, a supplement trade association, will not say vitamins prevent cancer.
"There is no vitamin or mineral supplement proven to reduce the risk of cancer," said Eric Jacobs, a senior epidemiologist and vitamin specialist with the American Cancer Society.
However, many doctors continue to recommend daily multivitamins for general health. And some experts say certain supplements may yet prove to be a help in the fight against cancer, once scientists can work out the right amounts and better ways to study their effects.
"I do think there is a fundamental issue of finding the optimal dose of essential nutrients," said Dr. Walter Willett, a professor of epidemiology and nutrition at the Harvard School of Public Health.
Experts say more research is needed.
"More than half of Americans are taking dietary supplements, mostly multivitamins, but scientists aren't certain about their benefit," said Dr. J. Michael McGinnis, who chaired the National Institutes of Health panel that critiqued supplemental vitamins.
"For something used so widely, at such expense, among Americans, there is simply a need for much better information," he said.
Scientists once suspected vitamin E and beta-carotene prevented lung cancer after a study showed people who took supplements appeared to have lower cancer incidence.
But a larger, more scientifically rigorous study found 50 milligrams a day of alpha-tocopherol, a form of vitamin E, had no effect on lung cancer incidence. And 20 milligrams of beta-carotene, a precursor of vitamin A, actually increased lung cancer incidence in smokers by 18 percent. Health officials now warn smokers not to take beta-carotene supplements, reports AP.