Carotenoid Intake, Vegetables, and the Risk of Lung Cancer Among White Men in New Jersey

A population-based incident case-control study of lung cancer in white males was conducted during 1980-1981 in six high-risk areas in New Jersey. Interviews were completed for 763 cases and 900 controls. To assess whether dietary intake of carotenoids, preformed retinol, or total vitamin A influences the risk of lung cancer, the authors asked the respondents about the usual frequency of consumption, approximately four years earlier, of 44 food items which provide 83% of the vitamin A in the US diet and about the use of vitamin supplements. The men in the lowest quartile of carotenoid intake had a relative risk of 1.3 compared with those in the highest quartile after adjusting for smoking. No increase in risk was associated with low consumption of retinol or total vitamin A. Intake of vegetables, dark green vegetables, and dark yellow-orange vegetables showed stronger associations than did the carotenoid index; the smoking-adjusted risks of those in the lowest quartiles of consumption of these food groups reached relative risks of 1.4-1.5 compared with the risks of those in the highest quartiles. The protective effect of vegetables was limited to current and recent cigarette smokers; the smoking-adjusted relative risks for low consumers reached 1.7, 1.8, and 2.2 compared with the risks for high consumers for vegetables, dark green vegetables, and dark yellow-orange vegetables, respectively. The reduction in risk with vegetable intake was most apparent for squamous cell carcinomas, but it extended to adenocarcinomas and most other cell types when only current and recent smokers were analyzed. This protection among current and recent smokers is consistent with the model that vegetable intake prevents a late-stage event of carcinogenesis. Consumption of dark yellow-orange vegetables was consistently more predictive of reduced risk than consumption of any other food group or the total carotenoid index, possibly because of the high content of beta-carotene relative to other carotenoids in this particular food group.