By Alexander Michels, 541-737-5085

Contact: Balz Frei, 541-737-5078 or

April 28, 2015

A press release from the American Association for Cancer Research (AACR) annual meeting in Philadelphia recently set off a wave of coverage about vitamin supplements increasing the risk for certain cancers in certain people. The comments originated from Dr. Tim Byers from the University of Colorado Cancer Center, as part of a presentation about the harms of over-supplementation with vitamins and minerals. At the Linus Pauling Institute, we would like to make clear that, while Dr. Byers’ statements were correct, they were not put into the proper context and lead to highly misleading headlines in the popular press. You certainly should not abandon your vitamin and mineral supplements without knowing the entire story behind these claims.

Vitamins – as their name implies – are essential for life. Without them, our body cannot function normally; we suffer from poor health, and eventually develop disease and die. However, just like any other molecule–even water or oxygen–taking too much of a good thing can be bad. As the famous quote attributed to Paracelsus states, “Poison is in everything, and no thing is without poison. The dosage makes it either a poison or a remedy.” Vitamins and minerals taken at doses recommended by the Institute of Medicine, also known as the Recommended Dietary Allowance or RDA, are the “remedy”; the same vitamins and minerals taken at doses far exceeding the RDA may have adverse health effects and, hence, could become a “poison.” The supplementation trials in human subjects that Dr. Byers quoted in his presentation have shown that only certain vitamins taken in excess of the RDA increased the risk of certain cancers, possibly by promoting the proliferation of cancer cells that already were present in these subjects.

What should not be ignored is that the scientific evidence supports the use of multivitamins (containing the recommended levels of vitamins and essential minerals) in the prevention of cancer. One of the largest, longest, and most carefully conducted human trials on multivitamins, the Physicians’ Health Study II, showed that the daily consumption of these supplements over 11 years reduced total cancer incidence by 8%, better than any pharmaceutical drug to date. This could translate into 130,000 fewer cancer cases in the U.S. every year. The Physicians’ Health Study II also showed that long-term use of multivitamins is completely safe, without any adverse health effects observed.

To give Dr. Byers proper credit, his words did support the position of the Linus Pauling Institute:  “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.”

Don’t read the headlines, focus on the evidence and decide for yourself!

Also, see the responses from our colleagues on why journalism on nutrition topics is failing you and how vitamins are easy targets for misinformation.

Image credit: bradley j