High-fiber diet linked to lower lung disease risk

Mature grain, ready for harvesting, stands in a farmer's field near Goulburn, about 80km (50 miles) northeast of Canberra December 15, 2009.

NEW YORK (Reuters Health) - People who get enough fiber in their diets, particularly from whole grains, may have a lower risk of developing chronic lung disease than those who eat few high-fiber foods, a new study finds.

The study, of more than 100,000 U.S. adults followed between 1984 and 2000, found that those with the highest fiber intake at the outset had a lower risk of developing chronic obstructive pulmonary disease (COPD), a group of lung disorders that includes emphysema and chronic bronchitis.

Out of the 111,580 study participants, 832 were diagnosed with COPD during the study period, for a rate of less than one percent. Of those cases, 234 were diagnosed among the one-fifth of study participants with the lowest fiber consumption; while 107 cases were seen among the one-fifth with the highest fiber intake.

When the researchers accounted for a number of other factors -- including smoking, age, weight and exercise habits -- the group with the highest fiber intake still had a one-third lower risk of COPD than the group that consumed the least fiber.

The findings do not prove that fiber-rich foods help prevent COPD, according to the researchers, led by Dr. Raphaelle Varraso of the French national health institute

INSERM.

Smoking is the primary risk factor for COPD, and the extent to which diet may contribute to or help prevent the disease is still being studied.

However, experts already recommend that people try to bulk up their diets with fiber: men are advised to get anywhere from 30 to 38 grams per day, while women should strive for 21 to 25 grams.

In this study, the group with the highest fiber intake typically got about 28 grams per day -- suggesting that the recommended amount of fiber might be enough to have an effect on COPD risk.

"For COPD prevention, the most important public health message remains smoking cessation," Varraso's team writes in the American Journal of Epidemiology, "but our data suggest that diet, another modifiable risk factor, might also influence COPD risk."

The findings are based on data from two large U.S. studies of physicians, nurses and other health professionals. Participants completed detailed dietary questionnaires in 1984 or 1986, and again every few years thereafter. They also periodically reported on other lifestyle habits and any newly diagnosed medical conditions.

Overall, high fiber intake was related to a lower COPD risk. When the researchers analyzed the association between COPD and specific fiber sources -- grains, fruits and vegetables -- only fiber from grains was independently linked to lower odds of the lung disease once smoking and other factors were taken into account.

It is makes sense that fiber could have some effect on COPD risk, according to the researchers. The nutrient, they note, has both antioxidant and anti-inflammatory properties that could affect the development of chronic lung disease.

Still, Varraso's team points out, it is always difficult for studies to weed out the possible health effects of any single nutrient in the diet.

And the fact that grain fiber, in particular, was linked to COPD raises the possibility that components of whole grains other than fiber are at work, the researchers note. The complexity with which different food components interact is why experts usually emphasize the importance of a balanced, varied diet over any one nutrient.

SOURCE: American Journal of Epidemiology, online February 19, 2010.