Vitamin A, Cigarette Smoking, and Airway Obstruction

The hypothesis that vitamin A, or foods rich in vitamin A such as milk, protects against the development of airway obstruction was tested in a subsample of data from the 1971–1975 National Health and Nutrition Examination Survey. The relative risk (estimated by relative odds) of having airway obstruction, defined as a FEV1/FVC ⩽ 65%, was measured for different levels of nutrient and food group intakes after adjustment for age, sex, Quetelet Index, caloric intake, and cigarette smoking. Among the white respondents (never smokers or current smokers) whose recalled diet could be considered as typical of their usual diet, the relative odds of having airway obstruction was inversely related to vitamin A intake (χ2 for trend = 7.2, p < 0.01). In the analysis by food groups, the adjusted relative odds of airway obstruction for meat and poultry were 2.4 (95% confidence limits: 1.0 to 5.8) and for milk 1.6 (95% confidence limits: 1.0 to 2.5). The association of airway obstruction with lack of vitamin A or milk int...