Vitamin C Supplements May Be Harmful

June 15 -- A new laboratory study suggests vitamin C supplements may actually help produce toxins that can damage DNA, which could be a first step in the development of cancer cells.

In the study appearing today in the journal Science, researchers from the University of Pennsylvania found the nutrient can act as a catalyst to help make a toxin that can injure the body's genetic code.

ABCNEWS' Dr. Tim Johnson said the study is too preliminary for anyone to jump to conclusions about vitamin C supplements, although people should not overuse them.

"There is a study showing that in the test tube — and I stress, in the test tube — that vitamin C may actually cause the DNA damage and that might increase the risk for cancer. I stress the might," said Johnson on ABCNEWS' Good Morning America.

The lead author of the study, Ian Blair, said the research does sound a warning about the use of vitamin C pills, but the findings do not mean that vitamin C causes cancer.

Don't Go Overboard

Johnson said the bottom line, when it comes to this study, is to acknowledge that we should not overdo any supplements. "I think it says to us, let's get our vitamins from a good, balanced diet and not take megadoses of supplements," he said.

In the study, researchers analyzed the effects of vitamin C on lipid hydroperoxide, a compound produced in the body from fat in the diet. Lipid hydroperoxide can be converted in the cell into agents, called genotoxins, that can damage DNA. The researchers found that vitamin C was highly efficient in converting lipid hydroperoxide into the gene-damaging toxins.

Johnson said that because the results of the study come from laboratory tests involving chemicals in glass lab dishes, the same action may not occur in living animals.

Vitamin C pills grew in popularity in the 1970s after Linus Pauling, a Nobel Prize-winning chemist, said large doses of the vitamin were good for people.

Today doctors have different ideas about whether or not vitamin C supplementation is a good idea. Some say large doses have not been proven to be beneficial in clinical studies.