Diet and lung cancer in California Seventh-day Adventists.

The Adventist Health Study, a cohort study of 34,198 California Seventh-day Adventists, identified 61 cases of new primary lung cancer over 6 years of follow-up (1977-1982). The population studied was unique in that only 4% admitted to current cigarette smoking and about half were lacto-ovovegetarians. A total of 36% of the lung tumors were adenocarcinomas, and 19% were squamous cell carcinomas. The expected associations with cigarette smoking were noted for Kreyberg group I tumors (squamous cell, large cell, and small cell carcinoma; relative risk (RR) = 53.2 for current smokers and 7.07 for past smokers), but much lesser associations were noted for Kreyberg group II tumors (adenocarcinoma and bronchoalveolar carcinoma; RR = 1.99 for current smokers and 1.59 for past smokers). In this study, fruit consumption was the dietary constituent that showed a strong, statistically significant protective association with lung cancer that was independent of smoking (fruit consumption less than 3 times/week, RR = 1.0; 3-7 times/week, RR = 0.30; greater than or equal to 2 times/day, RR = 0.26). This association was somewhat stronger for Kreyberg group II tumors, but similar trends were also noted for Kreyberg group I tumors. Confounding with smoking seems unlikely in a population with very few current smokers and where both stratification and Cox modeling methods of analysis led to similar conclusions.