Cancer survivors turn to supplements too soon, suggests review

By Lorraine Heller

- Last updated on GMT

Related tags: Cancer

Many cancer survivors report taking vitamin and mineral
supplements, despite inconclusive evidence of the benefits,
according to a review of scientific literature.

Conducted by researchers at Fred Hutchinson Cancer Research Center and published in the Journal of Clinical Oncology last week, the review involved 32 studies published between 1999 and 2006. The research was funded by the National Cancer Institute. The researchers found that 64 to 81 percent of the nation's 10 million adult cancer survivors reported using vitamins or minerals (excluding multivitamins), whereas in the general population only 50 percent of adults reported taking dietary supplements. However, despite the high incidence of supplement usage, the researchers cautioned that there is not yet enough evidence that vitamin and herbal supplements can reduce the adverse effects of cancer treatment, decrease the risk of cancer recurrence or improve a patient's chances of survival. "While supplement use may be beneficial for some patients, such as those who cannot eat a balanced diet, research suggests that certain supplements may actually interfere with treatment or even accelerate cancer growth,"​ said senior author Cornelia Ulrich, an associate member of the Hutchinson Center's Public Health Sciences Division. According to the review, survivors of breast cancer reported the highest use, of 75 to 87 percent. Prostate-cancer survivors reported the least use, of 26 to 35 percent. In general, patients most likely to take supplements were more highly educated. Also, females reported higher supplement use than males. The researchers also found that many people initiate the use of vitamins and supplements after cancer diagnosis; between 14 percent and 32 percent started taking them after learning they have cancer. "Cancer survivors report that they hope to strengthen their immune system with supplement use or gain a sense of control and empowerment,"​ Ulrich said. However, many of these patients self-prescribe the supplements, without informing their physicians of the decision. But according to the researchers, knowing about supplement use is crucial, she continues, because of potential adverse effects. "Evidence clearly suggests the need for caution. 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." ​The authors said that until such research is conducted, health care professionals need to communicate with their patients about supplement use. "A simple explanation that medical studies show supplement use may not always be beneficial may help cancer survivors make well-informed decisions,"​ they wrote.

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