Could your daily vitamin pills increase the risk of cancer?

Dietary supplements may increase the risk of cancer if you take too many of them, according to an investigation by University of Colorado Cancer Center doctor Tim Byers, who presented his work to the American Association for Cancer Research (AACR) annual meeting. 

He assessed research going back 20 years ago when it was first noted that people who ate more fruits and vegetables were less likely to develop cancer. Byers wanted to see if taking extra vitamins and minerals would reduce cancer risk even further.

“We studied thousands of patients for 10 years who were taking dietary supplements and placebos. We found that the supplements were actually not beneficial for their health. In fact, some people actually got more cancer while on the vitamins,” he said.

One trial exploring the effects of beta-keratin supplements showed that taking more than the recommended dosage increased the risk for developing both lung cancer and heart disease by 20%.

A trial last year suggested that Vitamin E and Selenium, which had been hoped would reduce the risk of developing prostate cancer, actually did the opposite.

Folic acid, which was thought to help reduce the number of polyps in a colon, actually increased the number in another trial.

“This is not to say that people need to be afraid of taking vitamins and minerals,” says Byers. “If taken at the correct dosage, multivitamins can be good for you. But there is no substitute for good, nutritional food.”

Byers says that people can get the daily recommended doses of vitamins and minerals in their diets by eating healthy meal and that many adults who take vitamin supplements may not need them.

“At the end of the day we have discovered that taking extra vitamins and minerals do more harm than good,” says Byers.

Bill Condie

Bill Condie

Bill Condie is a science journalist based in Adelaide, Australia.

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