About a third of American adults take some type of multivitamin on a regular basis. In nearly every case, the goal is better health, even though there is no firm evidence to support this hope. The absence of benefit is one thing, but the presence of harm is another: A 2007 report in the Journal of the National Cancer Institute concluded that there was an increased prostate cancer risk among men using multivitamins, reports the October 2007 issue of Harvard Men’s Health Watch.

When scientists further explored this finding, they found no link between multivitamin use and the risk of developing localized prostate cancer. But they did find that men who take multivitamins more than once a day were 32% are more likely to develop advanced prostate cancer and 98% more likely to die from the disease.

However, the study had its limitations. For example, it was not designed to determine whether multivitamins actually caused cancer; it did not ascertain which multivitamins were taken; and the results failed to establish a relationship between dose and response. Moreover, other studies have shown no connection between prostate cancer and multivitamins. Faced with this contradictory information, scientists know they need more studies, and several are already under way.

Meanwhile, what should you do? Harvard Men’s Health Watch suggests that a good diet and other lifestyle changes may help lower your prostate cancer risk. As for vitamins, the new study cautions against excessive multivitamin use, but it does not show harm from a daily supplement that sticks to the recommended daily amounts of the standard vitamins. Above all, the new study adds to the growing body of evidence that tells us not to count on supplements.