Diabetes Mellitus: A Prospective Population Based Cohort Study of Norwegian Women

Background: The effects of fish consumption and n-3 fatty acids on type 2 diabetes mellitus (T2DM) have recently been debated. Objective:We explored the risk of T2DM in relation to consumption of lean fish, fatty fish, fish products and total fish as well as cod liver oil supplements in a representative sample of Norwegian women. Design: This was a prospective population based cohort study in 33740 women free of T2DM, stroke, angina or heart attack and with detailed information on important co-variates and dietary intake at baseline. Risk ratios and corresponding 95 % CI were estimated using Poisson regression with log-person time as offset. Results: Lean fish consumption was inversely associated with T2DM compared to zero intake. Risk ratios and 95 % CI for intake of 75 and 100 g lean fish per day were 0.71 (0.51, 0.98) and 0.67 (0.46, 0.98), respectively. There was no effect of intake of fatty fish, fish products, total fish or use of cod liver oil supplements on the risk of T2DM. Conclusion: Lean fish consumption of 75–100 g/d had a beneficial effect on T2DM. It remains unclear whether lean fish in itself has a protective effect on T2DM or that lean fish consumers have a protective life-style that we were not able to take into account in this study. Unfavorable effects of fatty fish consumption or use of cod liver oil supplements on T2DM were not observed