Sept. 24, 2004 -- Vitamins and minerals may appear to be safe because they are sold as over-the-counter remedies. But a new study shows that vitamin supplements may affect chemotherapy -- for better or worse.
Patients may think supplements are safe because they're "natural" products, but there is growing evidence that they can intensify or weaken the effects of chemotherapy drugs, say the researchers.
With many supplements on the market, scientists don't yet know how each affects chemotherapy.
But the pool of knowledge has now expanded with a new study from the University of Vermont in Burlington.
In a small study of 49 women undergoing chemotherapy for breast cancer, researcher Richard Branda, MD, of the University of Vermont's department of medicine and Vermont Cancer Center asked the women what supplements they took.
The women were at various stages of their disease. Some were newly diagnosed; others had been battling breast cancer's advanced stages.
Most women (71%) in the study took supplements, and the average number of supplements taken was three. But some took as many as 20 different supplements per day. The three that were most commonly used were multivitamins, vitamin E, and calcium.
Supplementation with vitamins, especially vitamin E, has been recommended to decrease the toxicity of cancer drugs, according to the authors.
Much of the toxicity associated with chemotherapy is related to a decrease in cells that help fight infection, leaving victims susceptible to infection.
Those who reported taking a multivitamin or vitamin E supplement retained more of an important kind of infection-fighting cell than those not taking such supplements.
In contrast, women who said they took folate supplements lost more of those same cells than other participants.
Vitamin B-12 did not appear to affect the number of the infection-fighting cells, which are called neutrophils. Neutrophils are white blood cells that help fight infections. Their ranks may be thinned as a side effect of chemotherapy.
Experts don't know exactly how supplements affect chemotherapy.
"The beneficial effects of vitamin supplementation and herbal remedy use on the efficacy of chemotherapy and patient survival remain unclear," write the researchers.
Their work appears in the Sept. 1 issue of the journal Cancer.
Larger studies are needed to explore the topic further.
Meanwhile, it's a good idea to let your health-care provider know what supplements (including herbal remedies) you're taking.
The advice applies to everyone, not just women undergoing chemotherapy.
That way, providers can watch out for possible interactions with other medications and health conditions.