Multivitamins may not slow colon cancer

Taking a multivitamin is unlikely to help colon cancer patients in battling the disease, suggests a new study.

"There is widespread belief among cancer patients that taking multivitamins will help to treat their cancer and prolong life," lead researcher Dr. Kimmie Ng of the Dana-Farber Cancer Institute, in Boston, told Reuters Health in an e-mail.

Because 26 to 77 percent of cancer survivors report using the supplements, Ng and her colleagues wanted to see what impact, if any, these multivitamins really had on colon cancer recurrence and survival.

The team followed more than 1,000 individuals who had recently undergone surgery for advanced (stage III) colon cancer, which, combined with rectal cancer, is the third most diagnosed cancer in both men and women in the U.S.

About half of the patients reported multivitamin use during, and six months after, completion of their chemotherapy, report the researchers in the Journal of Oncology. (The study was partially funded by Pfizer, makers of a popular brand of multivitamins, as well as a colon cancer therapy.)

The study found no improved survival or extension of time to disease recurrence among those taking multivitamins compared to nonusers, even after adjusting for other relevant factors such as age and family history of cancer.

Of course, the finding doesn't rule out the possibility that certain vitamins might still be helpful in fighting off cancer. Some earlier studies have hinted at a protective effect from vitamin D, for instance, although at much higher doses than those found in standard multivitamins.

The 400 IU of vitamin D in multivitamins are unlikely to significantly increase levels of the vitamin's active form in the blood, noted Ng.

"This current study adds to a growing body of research that questions the purported benefit of multivitamin use," she said. "And it underscores the need to investigate the use of individual vitamins, such as vitamin D, which may, in fact, provide real benefit."

The results don't specifically address the question of whether vitamins can help to prevent cancers either, noted Ng.

Marian L. Neuhouser of Fred Hutchinson Cancer Research Center in Seattle led a recent Women's Health Initiative study that found no benefit of multivitamins in cancer prevention. She noted in an e-mail to Reuters Health that the take-home message from both studies is similar: "Multivitamins do not prevent cancer and they do not improve cancer prognosis."

However, Neuhouser added that the results from the new study can really only be applied to colon cancer patients.

Enthusiasm for multivitamins is nevertheless "dampened," said Ng, given her negative results on top of already conflicting evidence for the use of multivitamins in cancer prevention.