Washington - There's more worrisome news about vitamins: Taking too many may increase men's risk of dying from prostate cancer.
The study, being published today, doesn't settle the issue. But it is the biggest yet to suggest high-dose multivitamins may harm the prostate, and the latest chapter in the confusing quest to tell whether taking various vitamins really helps a variety of conditions - or is a waste of money, or worse.
Government scientists turned to a study tracking the diet and health of almost 300,000 men. About a third reported taking a daily multivitamin, and 5 percent were heavy users, swallowing the pills more than seven times a week.
Within five years of the study's start, 10,241 men had been diagnosed with prostate cancer. Some 1,476 had advanced cancer; 179 died.
Heavy multivitamin users were almost twice as likely to get fatal prostate cancer as men who never took the pills, concludes the study in the Journal of the National Cancer Institute.
But overall, the researchers found no link between multivitamin use and early-stage prostate cancer.
The researchers speculate that perhaps high-dose vitamins had little effect until a tumor appeared, and then could spur its growth.
While similar but smaller studies have suggested a link, too, more rigorous research is needed, caution the National Cancer Institute scientists.