Multivitamins No Magic Bullet for Cancer Patients
October 13, 2010
By Melissa Weber
Can a simple multivitamin improve a cancer patient’s survival odds? Many seem to think so. As many as 3 out of 4 patients say they take multivitamins, believing that a daily dose of extra vitamins and minerals will bolster their immune system and make treatment more effective.
It may sound reasonable enough. But experts say it isn’t clear cut.
“Research seems to be pretty consistent that multivitamins do not seem to improve prognosis or survival after cancer treatment,” says Kim Robien, PhD, RD, a cancer and nutrition researcher with the University of Minnesota School of Public Health in Minneapolis.
But researchers have only scratched the surface of this complex topic. According to Robien, few studies have looked at the effects of multivitamins during and after cancer treatment. “Many questions have yet to be answered,” she says.
To take or not to take?
Multivitamins may not help—but they also probably don’t hurt, according to a recent study in colon cancer
patients reported in the Journal of Clinical Oncology
. Taking a multivitamin during and after treatment for stage 3 colon cancer didn’t reduce the risk of the cancer coming back, nor did patients live any longer compared with nonusers. Even so, researchers didn’t find any evidence that the supplement interacted with chemotherapy or had any other harmful effects, says the study’s leader, Kimmie Ng, MD, a gastrointestinal oncologist at Dana-Farber Cancer Institute in Boston.
“The majority of my patients end up asking at some point during their initial consultation whether they should be taking a multivitamin,” Ng says. “After doing this study, I now tell patients that although it isn’t detrimental to your outcomes, we have not been able to find any proof that it will improve your survival or the rate of cancer recurrence.”
Helpful in the face of eating difficulties
Without such proof, Robien says the only time multivitamins may truly be needed is when patients are unable to eat a well-balanced diet for a week or longer. “When people experience severe nausea, vomiting, or mucositis as a result of treatment… multivitamins are important for preventing nutrient deficiencies.”
But patients shouldn’t rely on multivitamins, Robien cautions, because they don’t provide the calories, protein, fat, and fiber the body needs to recover from cancer treatments. She says multivitamins are only as good as the nutrients that scientists have identified and isolated in order to put into tablet form. Whole foods, meanwhile, contain chemical components that researchers have yet to identify.
For patients unable to eat a diet with enough nutrients, the American Cancer Society suggests a standard multivitamin and mineral supplement that contains about 100% of the daily requirements.
Beware high doses
But don’t go overboard. Research shows that the risk of some cancers may rise in the setting of large—or “mega”—doses of individual nutrients, such as folic acid and beta carotene.
Other nutrients, particularly vitamins A, D, and K, stay in the body longer and can reach toxic levels when taken in very large doses.
More answers on the way
Researchers are ramping up their pursuit of which lifestyle and diet behaviors patients and survivors can adopt to improve their chances of survival. For metastatic colorectal cancer patients, for example, Ng and her colleagues plan to test whether adding vitamin D supplements to chemotherapy can improve survival. “Out of all the nutrients, I think vitamin D is the most interesting and has the most promising data for perhaps providing a real benefit,” Ng says.
Vitamin supplements may also someday be packed with a personal touch. Just as doctors are “personalizing” cancer medicine to match specific characteristics of the tumor, scientists hope to customize vitamin regimens to match a patient’s genes. From a simple blood sample, researchers can analyze a patient’s DNA to pinpoint variations in their genes. If those variations change the blood levels—and consequently, the action—of certain vitamins, doctors could ideally improve cancer outcomes, says Ng, who is currently testing how alterations in a patient’s DNA affect levels of vitamin D in the blood.
But concrete recommendations from such studies are still far in the future. For now, patients must wait for research to catch up with widespread use. At M.D. Anderson Cancer Center in Houston, clinical nutrition supervisor Linda Pataki, RD, LD, tells her patients it’s safe to take a standard multivitamin, but “it’s not a magic wand.”
“I’m an advocate for getting nutrients from the diet,” Pataki says. “If they can meet their vitamin and mineral needs through healthy food choices… that’s what I recommend for people to do.”
Citations: “Multivitamin Use Is Not Associated With Cancer Recurrence or Survival in Patients With Stage III Colon Cancer: Findings From CALGB 89803.” Published ahead of print on Aug. 30, 2010 in the Journal of Clinical Oncology. First author, Kimmie Ng, Dana-Farber Cancer Institute.
“Nutrition and Physical Activity During and After Cancer Treatment: An American Cancer Society Guide for Informed Choices.” Published in the November/December 2006 issue of CA: A Cancer Journal for Clinicians. First author, Colleen Doyle, American Cancer Society.
ACS News Center stories are provided as a source of cancer-related news and are not intended to be used as press releases.