Heavy multivitamin use linked to prostate cancer

While regular multivitamin use is not linked with early or localized prostate cancer, taking too many multivitamins may be associated with an increased risk for advanced or fatal prostate cancers, according to a study in the May 16 issue of the Journal of the National Cancer Institute.

Researchers have wondered what impact multivitamin use might have on cancer risk. A research team from the National Cancer Institute in Bethesda, Md., and colleagues followed 295,344 men enrolled in the National Institutes of Health-AARP Diet and Health Study to determine the association between multivitamin use and prostate cancer risk.

After five years of follow-up, 10,241 men were diagnosed with prostate cancer, including 8,765 with localized cancers and 1,476 with advanced cancers.

The researchers found no association between multivitamin use and the risk of localized prostate cancer. But they did find an increased risk of advanced and fatal prostate cancer among men who used multivitamins more than seven times a week, compared with men who did not use multivitamins.

The association was strongest in men with a family history of prostate cancer and men who also took selenium, beta-carotene, or zinc supplements.  For example, men who used a zinc supplement in addition to heavy multivitamin use were more than four times as likely to develop fatal prostate cancer than men who used only a multivitamin daily or less than daily.

This "could be due to nonessential, potentially harmful trace elements contained in zinc supplements, such as cadmium, a known carcinogen," the researchers said.

The researchers say that excessive intake of certain individual micronutrients that are used in combination with multivitamins may be the underlying factor that is related to risk and not the multivitamins themselves.

 "Because multivitamin supplements consist of a combination of several vitamins and men using high levels of multivitamins were also more likely to take a variety of individual supplements, we were unable to identify or quantify individual components responsible for the associations that we observed," the authors write.

While similar smaller studies have also suggested a link between high-dose multivitamin use and prostate cancer - further studies are needed.

 

According to the Canadian Cancer Society, prostate cancer is the most common form of cancer for Canadian men.  It is estimated that 1 in 8 men will develop prostate cancer in their lifetime - usually after the age of 60, while 1 in 27 will die from the disease.