Multivitamins Under Fire: Boosting Cancer Risks in Men

Written By: Gloria Tsang, RD

Title: Founding Registered Dietitian

Alumni: University of British Columbia

Last Updated on:

Although physician-scientists and supplement manufacturers are often at odds, they don’t spend much time sparring over multivitamins. Health experts mostly don’t publicly support or refute multivitamin supplementation, reasoning that even if they don’t help, they won’t hurt either. However, the latest Harvard publication is among the first to recommend that men toss their multivitamins away.

Multivitamins and Cancer Link in Men

In the March 2008 issue, Harvard Men’s Health Watch notes that recent studies have linked multivitamin use to prostate cancer. More specifically, studies have linked high intake of folic acid to colon polyps, the precursors of colorectal cancer. Researchers speculate that a higher intake of folic acid, which was first added to grain products in the 1990s, may have contributed to an increase in colorectal cancers in the mid-90s.

Possible Culprit? Multi + Folic Acid Fortification

What does all of this have to do with multivitamins? Now that folic acid is added to so many grain products, a healthy diet combined with a multivitamin could boost a person’s daily folic acid intake to 1,000 mcg or more, potentially increasing the risk of colorectal cancer.

In December 2007, researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging cast doubt on the benefits of folic acid fortification in the Tufts Journal. They found that since the United States and Canada started fortifying enriched-grain products with folic acid in the mid-90s, cases of neural tube defects have decreased significantly – by as much as 50% in some studies. However, during the same period, 15,000 more cases of colorectal cancer were recorded in the United States and 1,500 more in Canada each year.

The Bottom Line

In light of this research, Harvard Men’s Health Watch suggests that the average man give up the multivitamin, at least until scientists solve the puzzle of folic acid and cancer. Ensure to speak with your doctor about starting or stopping your multivitamins.

As for the ladies taking multivitamins, since fortified foods are widely available, the National Institutes of Health panel of experts recommended choosing a multivitamin with amounts less than 100% of the daily value (% DV) of the included ingredients to avoid overdose.


cancer, folic acid, men's nutrition, multivitamins


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