Risks and side effects

Like drugs, dietary supplements have risks and side effects. They can usually be used safely within certain dosage guidelines. But, unlike drugs, dietary supplements are mostly self-prescribed with no input from informed medical sources like doctors, nurses, or pharmacists.

There’s a lot of wrong information out there. Even for those who are usually well informed, it can be hard to find reliable information about the safe use and potential risks of dietary supplements.

As part of its function to monitor supplement safety, the US Food and Drug Administration (FDA) tracks reports of illness, injury, or reactions from supplements. And supplement makers are now required to report serious harmful effects to the FDA. Between October 2010 and March 2011, an average of around 120 adverse events were reported each month, and the numbers appear to be growing.

Exposures to supplements (such as vitamins, herbs, protein powders, and botanicals) accounted for more than 29,000 calls to US poison control centers in 2009. Of these calls, more than 3,000 were reportedly treated in health care facilities. About 500 were described as moderate to severe outcomes, and there was one death.

Most people who suffer unexpected side effects, illnesses, or drug interactions from dietary supplements don’t call a poison control center or the supplement manufacturer. This means that the numbers we have are likely to be very low estimates of actual events.

Used properly, certain dietary supplements may help reduce the risk of some diseases, reduce discomfort caused by certain drugs or conditions, or simply make you feel better (improve your quality of life). But taking dietary supplements can be risky, especially for people who are getting cancer treatment.

Special problems for people getting cancer treatment

There are several ways that supplements can cause problems for people during cancer treatment. For example, some dietary supplements can cause skin sensitivity and severe reactions when taken during radiation treatment. People who are getting radiation treatments should talk to their doctors before taking any supplement.

People getting chemotherapy may be at higher risk for drug interactions if they take dietary supplements. There is also concern that antioxidants might interfere with cancer cell-killing treatments. Cancer experts often recommend that patients avoid dietary supplements altogether until their cancer treatment is over. But if you decide to take supplements anyway, be sure to let your doctor know exactly what you are taking.