October 2, 2008

Vitamin C May Affect Anti-Cancer Drugs

In studies of cancer cells and mice, vitamin C appears to substantially reduce the effectiveness of anti-cancer drugs, U.S. researchers said.

Dr. Mark L. Heaney of the Memorial Sloan-Kettering Cancer Center in New York said the same mechanism may affect patient outcomes, although this premise needs to be tested.

Heaney and colleagues found that every chemotherapy drug tested did not work as well if cells were pretreated with vitamin C, as they did on untreated cancer cells. In the cell culture experiments, 30 percent to 70 percent less cancer cells treated with vitamin C were killed depending on the drug tested.

The study, published in Cancer Research, said that in an animal model system, while chemotherapy kept untreated cancer in check, tumors grew more rapidly in mice that were given cancer pretreated with vitamin C.

Heaney said that the amount of DHA used in the experiments resulted in an intracellular buildup similar to what could be seen in cancer patients using large supplemental doses of vitamin C.

Cancer patients should eat a healthy diet, which includes foods rich in vitamin C, it is use of large doses of over-the-counter vitamin C that is worrisome, Heaney said.