Widespread vitamin and mineral use among cancer survivors

5 February 2008

A review of scientific literatature by researchers at Fred Hutchinson Cancer Research Center and published Feb. 1 in the Journal of Clinical Oncology, has determined that cancer survivors are using many vitamins and mineral supplements, despite inconclusive evidence about the benefit of doing so.

"Can vitamin and herbal supplements reduce the adverse effects of cancer treatment, decrease the risk of cancer recurrence or improve a patient's chances of survival? We don't really know. Research into these matters has been minimal," said senior author Cornelia (Neli) Ulrich, Ph.D., an associate member of the Hutchinson Center's Public Health Sciences Division. "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," she said.

A review of 32 studies conducted between 1999 and 2006 found that many of the nation's 10 million adult cancer survivors use nutritional supplements. The researchers (Cornelia Ulrich, PhD and Christine Velicer, PhD) found that 64-81% of cancer survivors overall reported using vitamins or minerals (excluding multivitamins), whereas in the general population only 50% of adults reported taking dietary supplements.

Survivors of breast cancer reported the highest use (75-87%), whereas prostate-cancer survivors reported the least (26-35%). Factors associated with the highest level of supplement use overall included a higher level of education and being female.

The researchers also found that many people (14-32%) start taking vitamins and supplements after they have been given a cancer diagnosis.

"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 cancer survivors who use supplements do not let their doctors know; 31-68% of cancer patients and survivors who use supplements may not disclose this information or their doctors may fail to record it in their charts.

"This is disconcerting and suggests that many physicians may not recognize the importance of understanding whether their patients are taking supplements," Ulrich said.

Knowing about supplement use is crucial, she continues, because of potential adverse effects. "Evidence clearly suggests the need for caution," Ulrich said. "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."

Until research clarifies the effects of vitamin use in cancer survivors, the authors urge health care professionals to communicate openly 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," the authors wrote.

References
Fred Hutchinson Cancer Research Center. Study finds widespread vitamin and mineral use among cancer survivors, although benefits of such use remain unclear. Accessed 8 Feb 08