Dietary vitamin A and prevalence of bronchial metaplasia in asbestos-exposed workers.

The purpose of this investigation was to examine the association between dietary intake of vitamin A in the form of retinol and provitamin A carotenoids and the prevalence of bronchial squamous metaplasia in a sample of asbestos workers from an industrial clinic. Bronchial biopsies were obtained from 49 asbestos workers. Pulmonary function testing was done and in-person interviews were conducted to estimate dietary intake of retinol and provitamin A carotenoids, tobacco exposure, and asbestos exposure. Results indicated that workers with metaplasia reported consuming a significantly lower intake of total vitamin A [2000 retinol equivalents (RE)/d] than did subjects without metaplasia (2710 RE/d, P = 0.02). Logistic regression analyses showed that higher intakes of retinol [odds ratio (OR): 0.31; 95% CI: 0.04, 2.44], provitamin A carotenoids (OR: 0.31; 95% CI: 0.03, 2.84), and total vitamin A (OR: 0.29; 95% CI: 0.03, 2.49) were associated with a nonsignificant reduction in the OR for metaplasia (highest quartile compared with lowest quartile, adjusted ORs). Current smoking (OR: 5.25; 95% CI: 0.50, 55.1) and former smoking (OR: 2.95; 95% CI: 0.31, 28.1) were associated with a nonsignificant increase in the OR for bronchial metaplasia compared with never smoking. Greater airway obstruction [decreased forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC)] was associated with an increased OR for metaplasia (OR: 2.86; 95% CI: 1.09, 7.69). These results suggest that a higher (ie, above the median) intake of vitamin A from foods decreases the risk of bronchial metaplasia in workers occupationally exposed to asbestos.