Dietary supplement use in cancer care: help or harm.

Conventional wisdom generally recommends complete avoidance of all dietary supplements, especially during chemotherapy and radiation. This interdiction persists, in spite of high rates of dietary supplement use by patients throughout all phases of cancer care, and can result in patients' perceptions of physicians as negative, thus leading to widespread nondisclosure of use. A review of the clinical literature shows that some evidence for harm does exist; however, data also exist that show benefit from using certain well-qualified supplements. Physicians should increase their knowledge base about dietary supplement use in cancer and consider all of the data when advising patients. Strategies that are patient-centered and reflect the complete array of available evidence lead to more nuanced messages about dietary supplement use in cancer. This should encourage greater disclosure of use by patients and ultimately increase safety and efficacy for patients choosing to use dietary supplements during cancer care.