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Smokers could benefit from even a modest addition of vitamin C to their diet, according to study by UC Berkeley and USDA
03 Feb 2000

By Robert Sanders Public Affairs

BERKELEY-- A study published this week in the American Journal of Clinical Nutrition shows clearly that smoking depletes the body of vitamin C, a powerful antioxidant that protects the body from disease. However, the study suggests that moderate supplementation can help smokers boost their vitamin C levels significantly.

Antioxidants such as vitamin C, vitamin E and carotenoids are thought to help the body fight off diseases ranging from cancer to heart disease, and help stave off the degenerative effects of aging.

The study indicates, too, that previous research that found depleted vitamin E and carotenoids in smokers may have been measuring the effect of poor diet, not smoking.

The study, conducted by scientists at the University of California, Berkeley, and the U.S. Department of Agriculture's Western Human Nutrition Research Center (WHNRC) in Davis, was designed specifically to separate the effects of diet and smoking on antioxidant levels in the body.

"The first piece of advice for smokers is, of course, stop smoking," said study leader Lynn M. Wallock, PhD, a scientist at UC Berkeley and the WHNRC. "Barring that, smokers can benefit by improving their diet to include more fruits and vegetables, which contain a balance of antioxidants and other nutritional benefits, like fiber and carotenoids.

"Or, they can take vitamin C supplements. Even with modest vitamin C supplementation, smokers can improve their plasma vitamin C levels substantially. However, no regimen of diet or supplementation can make up for the adverse consequences of smoking."

The study was conducted by Wallock, Bruce N. Ames, professor of molecular and cell biology at UC Berkeley; Jens Lykkesfeldt, Stephan Christen and Harry H. Chang of UC Berkeley; and Robert A. Jacob of the Western Human Nutrition Research Center, which is located at UC Davis but operated by the USDA.

Because nonsmokers with a poor diet showed increased levels of antioxidants in their blood after taking vitamin C and E supplements in the study, the results hint also that supplements can improve the health of those with poor diets. Supplements, however, cannot provide all of the health benefits of fruits and vegetables, Wallock cautions.

The researchers screened hundreds of male volunteers to find smokers and nonsmokers with poor diets, looking specifically for low intake of fruits and vegetables. Anyone taking vitamin supplements was screened out.

The reason, Wallock said, is that many previous studies of smokers have not distinguished the effects of smoking from the effects of a poor diet, which is common among smokers.

"Smokers tend to have poor diets, so some effects that have been found may not be the result of smoking, but the result of not eating well," she said.

The volunteers selected for the study averaged 2.7 servings of fruits and vegetables per day, as compared to the 5-9 servings recommended by the National Research Council and a minimum of two servings of fruit and three of vegetables per day.

In baseline comparisons between the smokers and nonsmokers, smokers were found to have significantly lower vitamin C levels in blood plasma than did nonsmokers. However, vitamin E, beta-carotene and lycopene levels were not significantly different between smokers and nonsmokers with a poor diet. Lycopene is the major carotenoid found in tomato products, while beta-carotene is found in carrots and other orange or red fruits and vegetables.

Wallock and her team divided the 37 smokers and 38 nonsmokers into two groups. One received a combined supplement containing vitamins C and E and folate (272 mg vitamin C, 31 mg alpha-tocopherol, 400 micrograms of folic acid). The other group received placebos.

After three months, the smokers who took supplements had tripled their blood levels of vitamin C to bring them up to normal levels. Nonsmokers taking supplements benefited slightly, too.

Plasma levels of vitamin E rose in both smokers and nonsmokers, but the supplement ­ which contained a form of vitamin E called alpha-tocopherol - actually decreased levels of another form called gamma-tocopherol. Though Wallock said the health effects of this are uncertain, at least one study by Ames and Christen several years ago showed that gamma-tocopherol is nearly as potent an antioxidant as alpha-tocopherol.

Wallock continues to analyze results of the study, including the effects of supplementation on antioxidant levels in sperm.

The study was supported by the Tobacco Related Diseases Research Program, the National Institute of Environmental Health Sciences of the National Institutes of Health and the USDA Agricultural Research Service.


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