February 11, 2008

Supplement Use Widespread Among Cancer Patients and Survivors

Photo of a man looking at a bottle of vitamins

Researchers have found that, while vitamin and mineral supplement use is widespread among cancer patients and survivors, up to 68% of physicians may not know when their patients are using them. The finding highlights the need for doctors to discuss supplement use with their cancer patients.

Many cancer patients and survivors believe that vitamin supplements can reduce treatment side effects, decrease the chances of cancer recurrence and improve their survival. However, studies addressing these topics are inconsistent or inconclusive—and many doctors worry that supplements can interact with cancer treatments or have other unintended consequences.

Drs. Christine M. Velicer and Cornelia M. Ulrich of the Fred Hutchinson Cancer Research Center wanted to investigate how widespread this problem might be. With funding from NIH's National Cancer Institute (NCI), the researchers analyzed 32 studies published between 1999 and 2006 that addressed vitamin and mineral supplement use among U.S. adult cancer patients and survivors. Their results were published in the February 1, 2008, issue of Journal of Clinical Oncology.

The researchers found extensive supplement use among cancer patients and survivors. In studies combining data from different types of cancer, 64-81% of survivors reported using some kind of vitamin or mineral supplements, and 26-77% reported taking multivitamins. Breast cancer survivors reported the highest use, with consumption of any vitamin or mineral supplements ranging from 67% to 87%, and multivitamin use ranging from 57% to 62%. In comparison, about half of all U.S. adults take vitamin or mineral supplements, and about a third use multivitamins.

The researcher also found that between 14% and 32% of survivors started using supplements after their diagnosis. Women and people with higher levels of education were more likely to use supplements. Strikingly, the study found that 31-68% of cancer patients and survivors who use supplements may not discuss it with their doctors.

Knowing about supplement use is crucial for doctors. Ulrich explained. "Some vitamins, such as folic acid, may be involved in cancer progression while others, such as St. John's wort, can interfere with chemotherapy. However, we really need more research to understand whether use of these supplements can be beneficial or do more harm than good."

This study highlights the need for more research into how dietary supplements affect cancer treatment, survival and quality of life. To that end, NCI is currently conducting a number of clinical studies into different food components, many provided as dietary supplements, to determine their impact on cancer prevention and therapy. In the meantime, it's important for doctors and cancer patients to discuss any supplement use.

—by Harrison Wein, Ph.D.

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