Vitamin C Pills May Injure DNA

W A S H I N G T O N, June 14, 2001 -- The vitamin C pills taken by millions of health-conscious people may actually help produce toxins that can damage their DNA, a step toward forming cancer cells, a laboratory study suggests.

In a study appearing Friday in the journal Science, Universityof Pennsylvania researchers said they found in test tubeexperiments analyzing the action of vitamin C that the nutrient canact as a catalyst to help make a toxin that can injure DNA, thebody's genetic code.

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

"Vitamin C can do some good things, but it can do some badthings as well," Blair said. "If you really wanted to becautious, you just wouldn't use supplementation [vitamin pills]."

Instead of pills, Blair said people can get all the nutrientsthey need through a balanced diet, particularly fruits, vegetablesand grains.

Understanding Vitamin C

Balz Frei, a professor at the Linus Pauling Institute at OregonState University, said the Blair study "is an important finding inunderstanding the chemistry of vitamin C." He cautioned that theresults come from a test tube study, which involves chemicals inglass lab dishes, and that the same action may not occur in livinganimals.

In the study, Blair and his colleagues analyzed the effects ofvitamin C on lipid hydroperoxide, a compound produced in the bodyfrom fat in the diet. Lipid hydroperoxide can be converted in thecell into agents, called genotoxins, that can damage DNA.

Blair said his group found that vitamin C was highly efficientin converting lipid hydroperoxide into the gene-damaging toxins.

"Just because you damage DNA doesn't mean you'll get cancer,"Blair said. "The cell has an exquisite repair mechanism forlesions in the DNA."

Blair said the research may explain the failure of studies thathave attempted to show vitamin C can protect against cancer.

"There are two camps — people who think vitamin Csupplementation is good for you and those who think it is bad foryou," he said. "There is a paucity of any scientific evidencethat it is really good for you."

The Pills Pauling Swore By

Vitamin C supplementation includes not just pills, but also theaddition of artificial forms of the nutrient to foods, such asjuices, cereals and even candies.

The popularity among health-conscious Americans for poppingvitamin C pills was boosted by Linus Pauling, a Nobel-prize-winningchemist who advocated large doses of the vitamin. He routinely took15 grams daily and was 93 years old when he died in 1994.

However, Frei, a nutrient expert at the institution named forPauling, said such large doses of vitamin C have not been proven tobe beneficial in clinical studies.

"The Linus Pauling Institute does not endorse megadoses," Freisaid. "Our advice is to eat a healthy diet rich in fruits andvegetables."

Vitamin C is an antioxidant. It neutralizes oxygen freeradicals, which are metabolic products in the cell that can damageDNA. Some researchers have speculated that because of itsantioxidant action, large doses of the vitamin could preventcancer, strengthen the immune system and prevent the common cold.

Clinical studies, though, have been disappointing, said Frei.

"Vitamin C does not prevent a cold," he said, although somestudies suggest the nutrient may hasten recovery.

Vitamin C can help patients lower high blood pressure, and Freisaid some studies have suggested that "people in a diseasestate," such as an infection, may be helped by vitamin C.

Asked if healthy people benefit from vitamin C supplements, hesaid: "I don't think we could say that."

The Institute of Medicine, an arm of the National Academy ofSciences, recommends that women need 75 milligrams of vitamin Cdaily and 90 milligrams for men. Smokers need an additional 35milligrams. These are levels easily achieved by a balanced diet.

Much more than that is generally useless, said Frei. A healthybody can absorb about 200 milligrams a day and the surplus iscarried away with urine.