Fish intake and type 2 diabetes in Japanese men and women: the Japan Public Health Center-based Prospective Study.

BACKGROUND Although fish intake can improve glucose metabolism, results of some prospective studies in Western populations suggest potential adverse effects of environmental contaminants in fish on type 2 diabetes risk. However, data from populations with high fish consumption are scarce. OBJECTIVE We prospectively investigated the association between fish intake and type 2 diabetes risk in Japanese adults. DESIGN The participants were 22,921 men and 29,759 women aged 45-75 y who completed a questionnaire of the second survey for the Japan Public Health Center-based Prospective Study and who had no history of diabetes. Diet was ascertained by using a 147-item food-frequency questionnaire. ORs of self-reported, physician-diagnosed type 2 diabetes over 5 y were estimated by using logistic regression. RESULTS During the 5-y period, 971 new cases (572 men and 399 women) of type 2 diabetes were self-reported. In men, fish intake was significantly associated with a decreased risk of type 2 diabetes; multivariable-adjusted ORs of type 2 diabetes for the highest compared with the lowest quartile of intake were 0.73 (95% CI: 0.54, 1.00; P-trend = 0.04) for total fish and seafood and 0.68 (95% CI: 0.50, 0.92; P-trend = 0.016) for small and medium fish (horse mackerel and sardine, saury and mackerel, and eel). Additional analysis by fat content of fish did not detect any significant association for each category. In women, fish intake was not appreciably associated with type 2 diabetes risk. CONCLUSION In a population with high fish and seafood intake, fish consumption was associated with a lower risk of type 2 diabetes in men but not in women.