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Antioxidants Cut Asthma Risk in Children

Reduction most dramatic among those exposed to secondhand smoke

FRIDAY, Feb. 13, 2004 (HealthDayNews) -- Children with high levels of antioxidants such as beta carotene and vitamin C have lower rates of asthma, a new study finds.

The reduction in asthma prevalence proved most dramatic among children exposed to secondhand smoke, Cornell University researchers report in the February issue of the American Journal of Respiratory and Critical Care Medicine.

"This study raises the possibility that dietary intervention may be something to consider for prevention or treatment of asthma," says study author Patricia Cassano.

Children with higher levels of a third antioxidant -- selenium, a mineral nutrient -- also had lower prevalence of asthma, researchers found.

Cassano, an assistant professor of nutritional epidemiology, and other experts stress the study does not establish a cause-and-effect relationship between the antioxidants and reduction in asthma. The findings, Cassano says, suggest the need for further research to understand if increases in antioxidants could prevent asthma's onset, its progression or both.

The Cornell researchers focused on 6,153 children, aged 4 to 16, who took part in the third National Health and Nutrition Examination Survey, conducted by the U.S. Centers for Disease Control and Prevention from 1988 to 1994. The researchers looked at results of a health exam, a household questionnaire on whether asthma had been diagnosed, and blood tests measuring antioxidant levels and exposure to cigarette smoke.

Children with higher levels of selenium had a 10 percent reduction in asthma prevalence compared with other children. In children exposed to secondhand smoke, the reduction associated with selenium climbed to 50 percent.

Higher beta carotene levels in children also were associated with a reduction in asthma -- by 40 percent among those exposed to secondhand smoke and by 10 percent among those not exposed to smoke. Higher vitamin C levels, too, were associated with reducing asthma, by about 40 percent for those exposed to smoke and by 10 percent for others.

Beta carotene is found in fruits and vegetables such as carrots, mangos and oranges. Vitamin C is plentiful in oranges and other citrus fruits, as well strawberries, red and green peppers, broccoli and Brussels sprouts. Selenium can be found in liver, cereals, grains, fish and some nuts. Supplements containing antioxidants also are available, but too much selenium can be toxic, the researchers note.

Another antioxidant, vitamin E, had little or no association with asthma prevalence regardless of smoke exposure.

Cassano says more research is needed to determine whether and how an increase in some antioxidants might reduce the occurrence of asthma.

Other research has linked chronic asthma and low levels of antioxidants in the lungs, and has suggested that drugs could be developed that fight asthma by preventing the decline of antioxidants during asthma attacks, experts say.

"I agree that antioxidants play a role in inflammation, and there might be a role for using these agents" in asthma patients, says Dr. Marianne Frieri, director of allergy and immunology at Nassau University Medical Center in East Meadow, N.Y.

With higher levels of antioxidants, "you can potentially help certain forms of asthma," says Frieri, who's also a professor of medicine at the Stony Brook University, part of the State University of New York. But, she adds, asthma has many different triggers.

The American Lung Association estimates that 6.3 million U.S. children under 18 have asthma, the leading serious chronic illness among children. The number of cases of asthma has been on the rise, but the reason why remains unclear.

Dr. Jerry Shier, a doctor at the Asthma and Allergy Center in Montgomery County, Md., calls the Cornell study "provocative" and says the possible relationship between antioxidants and asthma deserves further study.

"Everyone's looking for a reason why we should have this increase [in asthma cases], and this is one area -- nutrition," says Shier, an assistant clinical professor at George Washington University School of Medicine. "Has our diet changed, leading to an increase in asthma?"

More information

For more on asthma, visit the American Lung Association or the National Institute of Allergy and Infectious Diseases.

SOURCES: Patricia Cassano, Ph.D., assistant professor, nutritional epidemiology, Cornell University, Ithaca, N.Y.; Marianne Frieri, M.D., Ph.D., director, allergy and immunology, Nassau University Medical Center, East Meadow, N.Y., and professor, medicine, Stony Brook University, part of the State University of New York; Jerry Shier, M.D., Asthma and Allergy Center, Montgomery County, Md., and assistant clinical professor, George Washington University School of Medicine, Washington, D.C.; February 2004 American Journal of Respiratory and Critical Care Medicine
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