A case-control study of diet and lung cancer in Kerala, south India.

A total of 281 male lung-cancer patients were identified from the hospital cancer registry in the Regional Cancer Centre in Trivandrum. The controls were selected from the visitors and patients' bystanders in the hospital. The recruitment of cases and controls started in 1990, and the present study used the cases registered in the first year. The questionnaire administered to cases and controls collected information on tobacco smoking and alcohol habits. Dietary data were collected using a food frequency questionnaire and were analyzed by multiple logistic regression producing odds ratio estimates of the relative risk and deviance chi-squared tests of significance. Analysis was done on the computer package, EGRET. All models included age, education, religion and smoking to adjust for the effect of confounding. Green vegetables and bananas were found to have a protective association with lung cancer. The odds ratio associated with the highest quartile of vegetable consumption compared with the lowest was 0.32 (95% confidence interval 0.13, 0.78). Forward stepwise regression analysis indicated pumpkins and onions as the most consistently significant protective factors. Animal protein foods and dairy products were found to have a predisposing effect on lung cancer in this study. The expected influence of smoking on lung cancer (a considerable increase in risk among smokers) provided evidence of the reliability of the data. In conclusion the results from this study show that diet has a role in lung cancer aetiology, although the association is weak compared to the effects of smoking.