Risk modification in lung cancer by a dietary intake of preserved foods and soyfoods: findings from a case-control study in Okinawa, Japan.

To disclose the association of dietary intake of preserved foods and soyfoods with lung cancer risk, we analyzed the data from a case-control study conducted in Okinawa, Japan, from 1988 to 1991. The analysis, based on 333 cases and 666 age-, sex- and residence-matched population controls, provided the following major findings. (1) The more the miso soup intake, the higher the risk (test for trend: P = 0.001 for males; P = 0.043 for females). (2) Frequent intake of pickles (excluding salted fish) tended to be linked with an elevated risk in males. The adjusted odds ratio (OR) for once or twice per week or more, relative to less than once a month was 1.88 (95% confidence interval (CI): 1.26-2.81). (3) Frequent intake of soybeans was associated with a decreased risk in men (OR: 0.63, 95% CI: 0.40-0.98 for once or twice per week or more, relative to less than once a month). (4) Daily consumers of tofu were at a decreased risk, particularly for squamous cell carcinoma; the OR (95% CI) being 0.55 (0.34-0.89) in males and 0.14 (0.02-0.89) in females. These findings suggested deleterious effects of preserved foods and protective ones of soyfoods rich in isoflavones.