High-fiber diet may lower odds of asthma

Adherence to a high-fiber diet may aid in mediating systemic inflammation and decrease the risk for respiratory morbidity, including asthma, according to study results published in the Annals of the American Thoracic Society.

Muhammad A. Saeed, MD, research associate in the division of pulmonary, critical care and sleep at the College of Medicine at the University of Nebraska Medical Center, and colleagues analyzed data from 13,147 adults (aged 20-79 years; 69.5% non-Hispanic white; 54.5% nonsmokers; 7.8% with current asthma) who participated in the National Health and Nutrition Examination Survey 2007-2012 to examine the association between dietary fiber intake and asthma, respiratory symptoms and inflammation. Participants had complete information on individual fiber intake, total calorie intake, BMI, smoking status and socioeconomic level.

The lowest fiber intake was categorized as less than 10.46 g per day and the highest intake as more than 21.2 g per day.

Researchers observed an association between lower-fiber intake and increased risk for asthma (OR = 1.4 for lowest quartile vs. highest quartile of intake; 95% CI, 1-1.8; P = .027). The researchers also reported significant interactions between fiber and sex and race/ethnicity, with stronger associations for women and non-Hispanic white individuals.

Compared with high-fiber intake, lower intake was associated with increased risk for wheeze (OR = 1.3; 95% CI, 1-1.6; P = .018), cough (OR = 1.7; 95% CI, 1.2-2.3; P = .002) and phlegm (OR = 1.4; 95% CI, 1.1-2; P = .021).

Those with a lower-fiber intake had 1.6 times higher odds of having high serum C-reactive protein compared with those with high-fiber intake (OR = 1.6; 95% CI, 1-2.5; P = .0139).

“These findings support dietary guidelines by the U.S. Department of Health and Human Services recommending that Americans consume 20 to 35 g per day of both soluble and insoluble fiber,” the researchers wrote. “Further research is required to shed light on the mechanism of action of a high-fiber diet in reducing systemic inflammation and respiratory morbidity and large prospective trials in healthy populations are needed to validate the preventative properties of high-fiber diets and supplements.”