Getting an adequate amount of fiber each day may help middle-aged people breathe easier, and appears to benefit non-smokers and smokers alike.

Among 11,897 men and women, those with the highest daily fiber intake had better lung function and were less likely to have chronic obstructive pulmonary disease, or COPD, report Dr. Stephanie J. London and colleagues.

COPD includes conditions like emphysema and chronic bronchitis, which obstruct airflow to the lungs. Though smoking is the major risk factor for poor lung function and COPD, the researchers found the highest dietary fiber intake appeared to similarly protect both smokers and nonsmokers.

Most previous research looked at associations between antioxidant vitamins, or fruit and vegetable intake and lung function. “Our data suggest that perhaps it is fiber that is important,” said London, of the National Institute of Environmental Health Sciences, at Research Triangle Park, North Carolina.

The investigators analyzed information on dietary intake and the results of lung function tests from U.S. men and women, between 44 and 66 years old, who participated in the Atherosclerosis Risk in Communities Study between 1987 and 1989.

Nearly 15 percent of the study participants had COPD, they report in the American Journal of Epidemiology.

After separating participants by their average total fiber intake per day, the investigators found that those in the highest fifth of fiber intake (26.7 grams) had significantly better lung function than those in the lowest fifth (9.5 grams). The researchers report similar associations from cereal and fruit fiber, but not from vegetable fiber.

Moreover, the beneficial links remained even after accounting for other factors that may impact lung function such as dietary intake of vitamins C, D, and E; omega-3 polyunsaturated fatty acids; or cured meat; as well as weight, diabetes status, ethnicity, age, gender, and smoking status.

This study adds weight to some recent evidence that fiber protects lung function, London said. According to the National Academy of Sciences, adequate daily total fiber intake ranges from 30 to 38 grams for middle-aged men and from 21 to 25 grams for middle-aged women.

SOURCE: American Journal of Epidemiology, March 2008