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WASHINGTON - Vitamin C supplements may significantly reduce the effectiveness of several anti-cancer drugs, according to a new study published Wednesday.
In tests on isolated cancer cells in the laboratory, researchers found that 30 to 70 per cent fewer of the cells were killed if pretreated with vitamin C.
In studies of cancer cells in mice, studies found that tumours grew more rapidly if the animal was treated with chemotherapy and also given vitamin C supplements.
Researchers suggest that similar effects may occur in human patients.
"The use of vitamin C supplements could have the potential to reduce the ability of patients to respond to therapy," said Mark Heaney, an Associate Attending Physician at Memorial Sloan-Kettering Cancer Center, and lead author of the study.
Past studies have suggested vitamin C could be beneficial to cancer patients because it is an antioxidant. In August, a study showed that injected high does of vitamin C reduced the size of tumours and slowed cancerous growths by about 50 percent in laboratory mice.
The new research shows that a number of chemotherapy drugs produce "oxygen free radicals." According to the study's theory, vitamin C could "sop up the radicals," keeping cancer cells alive despite chemotherapy treatment.
Heaney said that he suspects vitamin C is good for cells in normal tissue, and extends cell life by protecting the all-important mitochondra, the cell's "power plant" that keeps it running.
"But that isn't what you want when you are trying to eliminate cancer cells," said Heaney.
All cancer therapy drugs work to disrupt the mitochondria, to push for cell
death.
The study notes that cancer patients should eat a healthy diet, including foods rich in vitamin C.
The study is published in the October 1 edition of Cancer Research. - AFP/ra
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