Risks and side effects of dietary supplements

Like drugs, dietary supplements have risks and side effects. But sellers aren’t required to do research studies in people to prove that a dietary supplement is safe. And 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 required to report serious harmful effects to the FDA. Early numbers are reported on the FDA website. Recent FDA information shows that the number of reports has continued to climb each calendar year:

    2010: 1,009 reports of dietary supplement adverse events

    2011: 2,047 reports of dietary supplement adverse events

    2012: 2,844 reports of dietary supplement adverse events

Exposures to supplements (such as vitamins, herbs, protein powders, and botanicals) accounted for more than 100,000 calls to US poison control centers in 2013. Of these calls, more than 8,000 people were reportedly treated in health care facilities. More than 1000 cases were reported to poison control centers as having moderate to severe outcomes. This did not include electrolyte and mineral supplements, which accounted for another 2,500 people treated in health facilities, with 350 moderate to severe reactions and 2 deaths reported to poison control centers.

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 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). And most people can use dietary supplements safely within certain dosage guidelines. 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.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Last Revised: March 31, 2015

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