here's more worrisome news about vitamins: Taking too many may increase men's risk of dying of prostate cancer.

A study, being published Wednesday, doesn't settle the issue. However, 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.

Karla Lawson of the U.S. National Cancer Institute in Bethesda, Md., and other 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 five per cent 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 Wednesday's Journal of the U.S. National Cancer Institute.

Here's the twist: 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 tumour appeared, and then could spur its growth.

While similar but smaller studies have also suggested a link, more rigorous research is needed, the National Cancer Institute scientists caution.

This newest study involves men who voluntarily took vitamins, and those at greatest risk — perhaps because they had a family history of the disease — may have been more likely to take the pills in hopes of avoiding their fate.

Individual supplements
Since multivitamins contain a combination of vitamins and men who took high doses of the pills were also more likely to take a variety of individual supplements, the researchers said they were unable to tell which components or how much increased the risk, the researchers said.

The findings "add to the growing evidence that questions the beneficial value of antioxidant vitamin pills in generally well-nourished populations, and underscore the possibility that antioxidant supplements could have unintended consequences for our health," Dr. Goran Bjelakovic, of the University of Nis in Serbia, and Dr. Christian Gluud, of Copenhagen University Hospital in Denmark, wrote in an accompanying editorial.

Prostate cancer is the most common cancer found in men and the second-most deadly, after lung cancer. Every day, 12 Canadian men die of prostate cancer.