DIETARY FLAVONOIDS AND THE RISK OF LUNG-CANCER AND OTHER MALIGNANT NEOPLASMS

Flavonoids are effective antioxidants and, in theory, may provide prot ection against cancer, although direct human evidence of this is scarc e. The relation between the intake of antioxidant flavonoids and subse quent risk of cancer was studied among 9,959 Finnish men and women age d 15-99 years and initially cancer free. Food consumption was estimate d by the dietary history method, covering the total habitual diet duri ng the previous year. During a follow-up in 1967-1991, 997 cancer case s and 151 lung cancer cases were diagnosed. An inverse association was observed between the intake of flavonoids and incidence of all sites of cancer combined. The sex- and age-adjusted relative risk of all sit es of cancer combined between the highest and lowest quartiles of flav onoid intake was 0.80 (95% confidence interval 0.67-0.96). This associ ation was mainly a result of lung cancer, which presented a correspond ing relative risk of 0.54 (95% confidence interval 0.34-0.87). The ass ociation between flavonoid intake and lung cancer incidence was not du e to the intake of antioxidant vitamins or other potential confounding factors, as adjustment for factors such as smoking and intakes of ene rgy, vitamin E, vitamin C, and beta-carotene did not materially alter the results, The association was strongest in persons under 50 years o f age and in nonsmokers with relative risks of 0.33 (95% confidence in terval 0.15-0.77) and 0.13 (95% confidence interval 0.03-0.58), respec tively. Of the major dietary flavonoid sources, the consumption of app les showed an inverse association with lung cancer incidence, with a r elative risk of 0.42 (95% confidence interval 0.23-0.76) after adjustm ent for the intake of other fruits and vegetables. The results are in line with the hypothesis that flavonoid intake in some circumstances m ay be involved in the cancer process, resulting in lowered risks.