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

We have examined the role of dietary patterns and specific dietary nutrients in the etiology of lung cancer among non-smokers using a multicenter case-control study.

506 non-smoking incident lung cancer cases were identified in the eight centers along with 1045 non-smoking controls. Dietary habits were assessed using a quantitative food-frequency questionnaire administered by personal interview. Based on this information, measures of total carotenoids, beta-carotene and retinol nutrient intake were estimated.

Protective effects against lung cancer were observed for high consumption 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 all 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 high levels of fruit consumption were restricted to squamous cell carcinoma (OR = 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). Similarly, any excess risk associated with meat, butter and egg consumption was restricted to squamous and small cell carcinomas, but was not detected for adenocarcinomas.

This evidence suggests that the public health significance of increasing vegetable consumption among the bottom third of the population would include a reduction in the incidence of lung cancer among lifetime non-smokers by at least 25%, and possibly more. A similar protective effect for increased fruit consumption may be present for squamous cell and small cell lung carcinomas.