Poor carbohydrate quality is associated with impaired lung function: A population-based cross-sectional analysis

Diet quality, particularly carbohydrate composition, may influence lung function; however, population-based evidence remains limited. This study aimed to examine the association between carbohydrate quality, assessed by the carbohydrate-to-fiber (CH:Fiber) ratio, and pulmonary function in U.S. adults. In fully adjusted models, each unit increase in CH:Fiber ratio was associated with lower forced vital capacity (FVC) (β = -0.03 L, 95% CI: -0.04 to - 0.02, P <.001) and FEV1 (β = -0.02 L, 95% CI: -0.03 to - 0.01, P <.001). Associations with peak expiratory flow and FEF25% to 75% were weaker but directionally consistent. Stronger inverse associations were observed among older adults, current smokers, and individuals with chronic bronchitis. Poor carbohydrate quality, indicated by a higher CH:Fiber ratio, is independently associated with lower lung function in U.S. adults. Diets emphasizing fiber-rich carbohydrate sources may support respiratory health. Future prospective studies and dietary intervention trials are needed to clarify causal relationships and elucidate the biological mechanisms linking carbohydrate quality to pulmonary function. We analyzed data from 11,414 adults aged ≥ 18 years from National Health and Nutrition Examination Survey 2007 to 2012 with valid dietary and spirometry data. Dietary intake was assessed using 24-hour recalls, and CH:Fiber ratio was calculated as total carbohydrate (g/day) divided by total dietary fiber (g/day). Lung function outcomes included FEV1, FVC, FEV1/FVC ratio, peak expiratory flow, and FEF25% to 75%. Multivariable linear regression models were applied, with subgroup and interaction analyses performed.