A multicenter case-control study of diet and lung cancer among non-smokers

Objective: We have examined the role of dietary patterns and specific dieta ry nutrients in the etiology of lung cancer among non-smokers using a multi center case-control study. Methods: 506 non-smoking incident lung cancer cases were identified in the eight centers along with 1045 non-smoking controls. Dietary habits were ass essed using a quantitative food-frequency questionnaire administered by per sonal interview. Based on this information, measures of total carotenoids, beta-carotene and retinol nutrient intake were estimated. Results: Protective effects against lung cancer were observed for high cons umption of tomatoes, (odds ratio (OR) = 0.5; 95% confidence interval (CI) 0 .4-0.6), lettuce (OR = 0.6; 95% CI 0.3-1.2), carrots (OR = 0.8; 95% CI 0.5- 1.1), margarine (OR = 0.7; 95% CI 0.5-0.8) and cheese (OR = 0.7; 95% CI 0.5 -1.0). Only weak protective effects were observed for high consumption of a ll carotenoids (OR = 0.8; 95% CI 0.6-1.0), beta-carotene (OR = 0.8; 95% CI 0.6-1.1) and retinol (OR = 0.9; 95% CI 0.7-1.1). Protective effects for hig h levels of fruit consumption were restricted to squamous cell carcinoma (O R = 0.7; 95% CI 0.4-1.2) and small cell carcinoma (OR = 0.7; 95% CI 0.4-1.2 ), and were not apparent for adenocarcinoma (OR = 0.9; 95% CI 0.6-1.3). Sim ilarly, any excess risk associated with meat, butter and egg consumption wa s restricted to squamous and small cell carcinomas, but was not detected fo r adenocarcinomas. Conclusions: This evidence suggests that the public health significance of increasing vegetable consumption among the bottom third of the population w ould include a reduction in the incidence of lung cancer among lifetime non -smokers by at least 25%, and possibly more. A similar protective effect fo r increased fruit consumption may be present for squamous cell and small ce ll lung carcinomas.