Link Found Between Cancer and Dietary Supplement Use

Taking over-the-counter supplements beyond the recommended amount could increase cancer risk.

Excessive use of over-the-counter supplements may carry an increased risk of cancer, according to the results of a recent study.

The study, presented at the annual American Association for Cancer Research meeting, indicates that taking more than the recommended amount of over-the-counter supplements can actually cause harm.

"We are not sure why this is happening at the molecular level but evidence shows that people who take more dietary supplements than needed tend to have a higher risk of developing cancer," researcher Tim Byers, MD, MPH, said in a press release.

The study noted that research began 20 years ago after it was observed cancer is less prevalent in people who eat more fruits and vegetables. The researchers sought to evaluate if taking extra vitamins and minerals could even further reduce the risk of cancer.

"When we first tested dietary supplements in animal models we found that the results were promising," Dr. Byers said. "Eventually we were able to move on to the human populations. We studied thousands of patients for ten years who were taking dietary supplements and placebos."

The actual results of excessive supplement use, however, was an unexpected outcome.

"We found that the supplements were actually not beneficial for their health,” Dr. Byers noted. “In fact, some people actually got more cancer while on the vitamins.”

An examination of the effects of beta-carotene supplements found that taking more than the recommended dosage increased the risk for both lung cancer and heart disease by 20%. In a different trial, the use of folic acid, previously thought to aid in reducing the number of colon polyps, actually increased the number of polyps.

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

The researchers concluded that many adults who use supplements don’t need them, while people can consume the daily recommended doses of vitamins and minerals by eating healthy food.

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