Prospective study of fruit and vegetable consumption and risk of lung cancer among men and women

Background: Diets high in fruits and vegetables have been shown to be assoc iated with a lower risk of lung cancer. beta -Carotene was hypothesized to be largely responsible for the apparent protective effect, but this hypothe sis was not supported by clinical trials. Methods: We examined the associat ion between lung cancer risk and fruit and vegetable consumption in 77283 w omen in the Nurses' Health Study and 47778 men in the Health Professionals' Follow-up Study. Diet was assessed with the use of a food-frequency questi onnaire that included 15 fruits and 23 vegetables. We used logistic regress ion models to estimate relative risks (RRs) of lung cancer within each coho rt, All statistical tests were two-sided, Results: We documented 519 lung c ancer cases among the women and 274 among the men. Total fruit and vegetabl e consumption was associated with a modestly lower risk of lung cancer amon g the women but not among the men. The RR for the highest versus lowest qui ntile of intake was 0.79 (95% confidence interval [CI] = 0.59-1.06) among t he women and 1.12 (95% CI = 0.74-1.69) among the men after adjustment for s moking status, quantity of cigarettes smoked per day, time since quitting s moking, and age at initiation of smoking. However, total fruit and vegetabl e consumption was associated with a lower risk of lung cancer among never s mokers in the combined cohorts, although the reduction was not statisticall y significant (RR = 0.63; 95% CI = 0.35-1.12 in the highest tertile). Concl usion: Higher fruit and vegetable intakes were associated with lower risks of lung cancer in women but not in men. It is possible that the inverse ass ociation among the women remained confounded by unmeasured smoking characte ristics, although fruits and vegetables were protective in both men and wom en who never smoked.