A new study suggests vitamin C taken in large doses can hamper the effectiveness of cancer drugs.
While the study focused on laboratory cancer cells and mice, it raises the question as to whether human patients might be subject to the same effects.
“There’s a chance, that taking vitamin C supplements can have a detrimental effect on cancer treatment,” said study author Dr. Mark L. Heaney, associated attending physician at Memorial Sloan-Kettering Cancer Center in New York City.
However, smaller doses of vitamin C, such as those found in common multivitamins and fruits and vegetables, does not appear to be an issue, he said.
Traditionally, vitamin C has not been considered a hindrance to cancer treatment. Quite the contrary, some scientists - including the late Linus Pauling – have long believed vitamin C has the potential to fight cancer.
Recent research suggested vitamin C can prevent cancer, although scientists are unsure why.
Vitamin C, an antioxidant, is found in fruits and vegetables and is also widely used as a powerful healing tool to treat many ills from colds to heart disease. It works by protecting cells from free radicals. A prolonged deficiency can lead to scurvy and death.
Researchers gave vitamin C to mice with tumors before they started chemotherapy treatment. The type of vitamin C used for the study is not readily available over-the-counter, but its equivalent to 2,000-mg dose for humans. Comparable to vitamin C found in 75 six-ounce glasses of orange juice. Supplements carrying that much of the vitamin can be found at health stores, he said.
Researchers concluded the vitamin had lowered chemotherapy effectiveness by 30 to 70 percent. They theorize that vitamin C may possibly disrupt the killing processes of chemotherapy and give protection to the cancer cells.
The next step is for researchers to launch clinical trials in humans, though, it may be difficult convincing patients to take high doses of vitamin C if it appears to counteract chemotherapy treatment, said Heaney.
“I recommend my patients continue eating a well-balanced diet that includes vitamin C, but that they don’t take any supplemental vitamin C. Multivitamins are fine,” he said.
While the new study appears to be credible, “the conclusions are drawn upon based on a small number of mice. A larger study would help to discern if this was a true trend or not,” said Dr. Chi Van Dang, director of the Johns Hopkins - Institute for Cell Engineering.
The study should be taken seriously by scientists. “But, additional studies are needed to find if vitamin C as a single agent can prevent cancer or the return of cancer once treated.”
The study is published in the October issue of the journal Cancer Research. #