Vitamin C Megadoses Hamper Cancer Treatments in Mice (HealthDay)

WEDNESDAY, Oct. 1 (HealthDay News) -- Large doses of vitamin Ccould reduce the effectiveness of anticancer drugs, according to a newstudy that focused on laboratory cancer cells and mice.

The finding raises questions about whether human patients might sufferthe same effects, the study authors said.

"There's a possibility that taking supplemental vitamin C could have adetrimental effect on cancer treatment," said study author Dr. Mark L.Heaney, associate attending physician at Memorial Sloan-Kettering CancerCenter in New York City.

However, there's no indication that smaller doses of vitamin C, such asthose found in food and ordinary multivitamins, might be a problem, hesaid.

Vitamin C has not traditionally been considered a hindrance to cancertreatment. In fact, some scientists -- including the late Linus Pauling -- have long viewed vitamin C as a potential cancer fighter. Recent researchhas suggested that vitamin C could help prevent cancer, but it's not clearwhy.

The vitamin, found in fruits and vegetables, also has a reputation as atreatment or preventive for a variety of ailments, including colds.

In the new study, Heaney and his colleagues gave doses of vitamin C tomice with tumors before they underwent chemotherapy. While the type ofvitamin C given to the mice isn't available over the counter, it's theequivalent of a 2,000-milligram dose for humans, Heaney said. That's theequivalent of the vitamin C found in 75 six-ounce glasses of orange juice.Supplements packing that much vitamin C are found in health stores, hesaid.

The researchers found that the vitamin C reduced the effectiveness ofthe chemotherapy by about 30 percent to 70 percent.

Heaney theorized that it's possible that vitamin C may disruptchemotherapy's killing processes and provide protection to the cancercells.

The findings were published in the October issue of the journalCancer Research.

Heaney said the next step is to launch studies with people, but, headded, it may be a "hard sell" to convince patients to take high-dosevitamin C supplements if it appears they counteract chemotherapy.

For now, he said, "What I recommend to my patients is that theycontinue to eat a well-balanced diet that has vitamin C, and that theydon't take supplemental vitamin C. I think a multivitamin is fine."

Dr. Chí Van Dang, who directs the Institute for Cell Engineeringat Johns Hopkins University School of Medicine, said the new study appearsvalid, "although some conclusions are based on small numbers of animals. Alarger number of animals could settle whether there is a real trend ornot."

Scientists should take the study seriously, he added, but the otherside of the equation must be examined, too. "Additional studies arenecessary regarding whether vitamin C as a single agent could preventcancer or the recurrence of cancer once treated."

Pamela Mason, scientific adviser and spokeswoman for the HealthSupplements Information Service, said, "The study concluded that vitamin Creduced the effectiveness of anticancer drugs in laboratory cell culturesand in mice with implanted cancer cells. Though the researchers said thattheir findings could have implications for human beings treated withanticancer drugs, they also added that this needs to be tested in a properclinical trial."

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