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White, oily fish consumption associated with lower risk for type 2 diabetes
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Consuming white, oily fish more than once per week may reduce the risk for type 2 diabetes whereas high consumption of shellfish may increase this risk, according to recent data from the European Prospective Investigation of Cancer-Norfolk cohort study.
Researchers in the United Kingdom completed a prospective analysis of the EPIC-Norfolk study to assess if consumption of different types of fish and seafood was associated with future risk for developing type 2 diabetes. They analyzed 21,984 participants (12,183 women) aged 40 to 79 years. Researchers obtained health and lifestyle information via questionnaire, and height, weight and waist circumference via health examination at baseline.
Total fish intake
Median follow-up of 10.2 years yielded 725 incident cases of diabetes. Higher total fish intake was associated with a significantly lower risk for diabetes (OR=0.75; 95% CI, 0.58-0.96), after adjustment for age, sex, family history, education, smoking, physical activity, dietary factors and obesity.
Researchers reported a similar inverse association with diabetes risk and white fish and oily fish intakes; however, the associations were not significant after adjustment for obesity or dietary factors.
People who consumed one or more portions of shellfish per week had an increased risk for diabetes (OR=1.36), according to results of adjusted analyses.
“Total intake of both white and oily fish was associated with a lower risk for diabetes, reinforcing the public health message to consume fish regularly,” the researchers concluded. “Shellfish intake was associated with an increased risk for diabetes, which highlights the potential importance of seafood preparation and cooking methods. The increased risk for diabetes with shellfish intake requires further study.”
Patel PS. Diabetes Care. 2009; 32:1857-1863.
The latest report from the EPIC-Norfolk study indicates that consumption of oily fish was associated with a 25% reduction in incident diabetes. Omega-3 fatty acids from oily fish are known to lower triglycerides, improve hemorrheology and confer potential cardiometabolic benefits. The addition of diabetes prevention to those benefits strengthens the lipotoxicity hypothesis in the pathogenesis of type 2 diabetes. In the Zucker Diabetic Fatty rat model, elevation of plasma free fatty acids, plasma triglycerides and accumulation of islet triglycerides all precede the development of diabetes in a predictive and reproducible manner (Lee et al. PNAS.1994;91:10878-10882). Although no such temporal plasma and islet lipid data are available in humans, the current data from EPIC-Norfolk show that intake of oily fish (a rich source of omega-3 fatty acids) decreased diabetes risk. The putative mechanism for diabetes prevention likely involves reduction of triglycerides and/or lipotoxicity by protective substances in oily fish. The corollary is that the apparent 36% increase in diabetes risk from consumption of shell fish indicates a lack of the protective factor (and possibly presence of diabetogenic factors) in shell fish. Obviously, further studies are needed to replicate these findings, establish facts, and clarify the underlying mechanisms.
– Samuel E. Dagogo-Jack, MD
Endocrine Today Editorial Board member