Associations between Dietary Fat-Soluble Vitamins and Pulmonary Function and Airway Inflammation: A Cross-Sectional study

Background Pulmonary function and airway inflammation are key indicators of respiratory health. Dietary factors, particularly fat-soluble vitamins, may modulate these outcomes, yet their associations in general populations remain inadequately characterized. Methods We analyzed data from the National Health and Nutrition Examination Survey (NHANES) 2007–2012, including 9,328 adults. Fat-soluble vitamin intake (A, D, E, K) was assessed via 24-hour dietary recalls. Spirometry measures (FVC, FEV1, FEF25–75%) and fractional exhaled nitric oxide (FeNO) were used to assess pulmonary function and airway inflammation, respectively. Multivariable linear regression and generalized additive models were employed to evaluate associations, with adjustment for sociodemographic, lifestyle, and clinical factors. Results In fully adjusted models, vitamins A and D were positively associated with FVC ( β  = 0.04 mL and 3.72 mL per µg/day, respectively). Vitamins A and K were positively associated with FeNO ( β  = 1.1 ppb and 3.3 ppb per unit increase, respectively). Nonlinear inverted U-shaped relationships were observed for vitamins A and D with FEV1, with threshold points at 958 µg/day and 11.95 µg/day. Below these thresholds, each unit increase in vitamin A and vitamin D intake was associated with an increase in FEV1 of 0.07 mL and 4.15 mL, respectively. Subgroup analyses indicated significant interactions with BMI, particularly among overweight individuals. Conclusions Dietary intake of vitamins A and D is positively associated with lung function, while vitamins A and K are associated with elevated FeNO, suggesting a potential pro-inflammatory effect. These findings highlight the complex roles of fat-soluble vitamins in respiratory health and support the consideration of nutritional intake in respiratory disease prevention strategies.