August 8, 2003

Secondhand smoke effects reduced by vitamin C

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VUMC investigators participated in a study that shows that a daily dose of vitamin C may help reduce risk by those exposed to secondhand smoke. Photo by Dana Johnson

Secondhand smoke effects reduced by vitamin C

People exposed to secondhand smoke may benefit from daily vitamin C supplements, according to a study published this week in the journal Nutrition and Cancer.

Dr. Jason D. Morrow, F. Tremaine Billings Professor of Medicine and Pharmacology, participated in the research, which was led by investigators at the University of California, Berkeley.

Daily doses of 500 milligrams of vitamin C reduced one measure of the harmful effects of secondhand smoke. Study participants were nonsmokers who were exposed to the smoke of at least one cigarette per day, five days a week, in an indoor setting, putting them at increased risk for lung cancer and heart disease.

The researchers measured blood levels of compounds called isoprostanes that are produced in the body when free radicals – highly reactive molecules derived from oxygen – attack the lipids that form cell membranes. Cigarette smoke contains large amounts of free radicals.

Morrow and Dr. L. Jackson Roberts II, professor of Pharmacology and Medicine, discovered the isoprostanes in 1990. They and others have established that the compounds are a reliable biomarker for free radical damage, also known as oxidant stress.

“The isoprostanes are the most accurate measure to assess oxidant stress in vivo in human beings, and a number of them possess potent bioactivity and likely mediate the pathophysiological consequences of oxidant stress,” Morrow said.

Elevated isoprostane levels – and the oxidant damage that produced them – have been linked to heart disease, cancer, atherosclerosis, and other chronic diseases.

Isoprostane levels dropped significantly in study participants taking vitamin C and in those taking a mixture of vitamin C, vitamin E, and the antioxidant alpha-lipoic acid, compared to the levels in participants taking daily placebo capsules.

“These results are very encouraging,” Marion Dietrich, Ph.D., a UC Berkeley researcher and lead author of the study, said in a news release. “They show that vitamin C may help protect nonsmokers from the oxidative damage caused by secondhand smoke.”

The researchers cautioned against misinterpreting the study’s findings.

“The message of the study is clearly not that taking vitamin C makes smoking or exposing others to smoke okay,” Gladys Block, Ph.D., professor of Nutritional Epidemiology at UC Berkeley and principal investigator of the study, said in the news release. “But, if you are in a situation where you cannot escape frequent exposure to secondhand smoke, it may be worthwhile to take vitamin C supplements as a precautionary measure. And, as always, eat a diet rich in fruits and vegetables.”

The research was supported by the University of California Tobacco-Related Disease Research Program, the National Cancer Institute, and the Burroughs Wellcome Fund.