Warning: Too Many Dietary Supplements May Increase Cancer Risk


A large-scale study has shown that over-supplementation could be very bad for our health. (Photo: Corbis) 

Could it be possible that too many vitamins and minerals can bring about various forms of cancer? Yes, according to a large-scale study delivered during the American Association for Cancer Research (AACR) Annual Meeting 2015.

The research presented at this conference dates back 20 years, when scientists discovered that a diet rich in fruits and vegetables was shown to keep cancer at bay. Then study experts shifted their focus to over-the-counter supplements, assuming that consuming extra vitamins and minerals would also produce anti-cancer benefits.

First came the testing on animals and the results were encouraging. Scientists then studied thousands of patients—over 300,000—who were given either dietary supplements or a placebo over a 10-year period.

And their findings were alarming.

“We show that not only is supplementing your diet with vitamins that are found in a healthy diet unlikely to decrease your risk of developing cancer, but in some cases, taking more than the recommended daily allowance of these supplements can increase cancer risk,” lead investigator Tim Byers, MD, MPH from the University of Colorado Cancer Center tells Yahoo Health.  “More specifically, taking more than the recommended daily allowance of folic acid, Vitamin E and beta-carotene were all shown to increase cancer risk.”

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One trial showed that taking more than the required amounts of beta-carotene— which is known for its ability to improve immunity and enhance vision — in supplement form increased the risk for developing both lung cancer and heart disease by 20 percent. Men who took an excess of vitamin E were at a higher risk of being diagnosed with prostate cancer. And while folic acid — a B vitamin— was considered a possible remedy for reducing the number of polyps in the colon, it increased the number in another trial.

“There really is no strong hypothesis explaining why these dietary supplements increase cancer risk,” states Byers. “It may have to do with the body’s overall nutrient balance, in this case ‘imbalance.’ Or it may have to do with specific effects of over-consumption of specific supplements.”

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So should we avoid the vitamin aisle altogether? “Unfortunately, few Americans eat a well-balanced diet and hope to make up for this by taking dietary supplements,” says Byers. “My recommendation is to get your nutrients from a healthy diet. If you take vitamins or other dietary supplements, choose products that stay within the recommended daily allowance.”

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