Fruit and Vegetable Consumption and Lung Cancer among Smokers in Finland, Italy and The Netherlands

Abstract

Unquestionably, cigarette smoking is the dominant risk factor for lung cancer. In addition, epidemiological studies consistently show an inverse association between fruit and vegetable consumption and lung cancer risk. 1,2,3 However, critics point at the possible role of residual confounding by smoking, and suggest that results from cohort studies may be less consistent compared with those from case-control studies. 4 Therefore, we examined the relationship between plant food consumption and lung cancer mortality in a cohort of men, focusing on smokers at baseline. Around 1970, dietary intake of Finnish, Italian and Dutch middle-aged men participating in the Seven Countries Study was assessed using a cross-check dietary history. Smoking habits and other lifestyle factors were determined by a standardised questionnaire. For 3108 men complete baseline information was available, of which 1578 were baseline smokers. During 25 years of follow-up, 187 lung cancer deaths occurred, of which 149 were smokers at baseline. Relative risks and 95% confidence intervals for consumption in country-specific tertiles were estimated by Cox proportional hazard analyses, and statistical significance was determined by two-sided tests. Risk estimates were calculated for the total study population and per country, both univariately and adjusted for potential confounders, including pack-years of smoking. Fruit consumption was inversely associated with lung cancer mortality in the total group of baseline smokers. Among Finnish smokers, lung cancer risk tended to be reduced in men with a medium or high fruit intake compared with those with the lowest fruit intake; however, estimates were not statistically significant. In Italian smokers, fruit consumption and lung cancer mortality were not related. Fruit consumption was only statistically significant inversely associated in the Dutch cohort. Stratifying the total cohort of smokers according to intensity of smoking, revealed the most pronounced relationship among the heaviest smokers. Vegetable intake and lung cancer mortality were not statistically significant related, neither in the total study population nor in the countries separately. In conclusion, this study shows a lower lung cancer risk among heavier smokers consuming more fruits. For vegetable consumption no such relationship was observed.