Abstract and Introduction
OBJECTIVE —Ecological data suggest an inverse correlation between fish consumption and diabetes prevalence. However, epidemiological data on fish intake and diabetes incidence are controversial and inconclusive. Therefore, we aimed to assess the literature and determine the association between fish consumption and diabetes risk quantitatively.
RESEARCH DESIGN AND METHODS—Prospective cohort studies published through August 2011 in peer-reviewed journals indexed in PubMed were selected. Additional information was retrieved through Google or a hand search of the references from relevant articles. The weighted relative risk (RR) and corresponding 95% CI for incident diabetes was estimated using random-effects models.
RESULTS—A database was derived from nine eligible studies (12 independent cohorts), including 438,214 individuals with an average 11.4-year follow-up. Compared with those who never consumed fish or ate fish less than once per month, the pooled RR of incident diabetes was 0.99 (95% CI 0.85–1.16) for individuals who ate fish five or more times per week (P trend = 0.80). Similar results were found for long-chain n-3 polyunsaturated fatty acid intake. Study location was an effect modifier. An inverse association between fish intake and diabetes incidence was found by combining studies conducted in Eastern but not Western countries.
CONCLUSIONS—Accumulated evidence generated from this meta-analysis does not support an overall inverse association of fish or fish oil intake with incidence of diabetes. The null association was modified by study location (Eastern vs. Western countries), which may reflect the possible difference between Eastern and Western dietary patterns. Further studies are warranted.
Although cardioprotective effects of fish or long-chain n-3 polyunsaturated fatty acid (LCn3PUFA) intake have been documented, the role of these dietary factors in the development of diabetes remains uncertain. Since ecological data indicate low prevalence of diabetes in populations with a large amount of fish consumption and laboratory studies suggest that insulin sensitivity is directly associated with the content of LCn3PUFA in cell membranes, it has been hypothesized that fish or LCn3PUFA intake may provide beneficial effects on diabetes risk. In the past decade, a number of longitudinal studies have examined the association between fish intake and incidence of diabetes, but the findings are conflicting. Although some studies reported a significant inverse association, other cohort studies found a positive relation between fish consumption and incidence of diabetes after adjustment for various potential confounders. To provide a reliable quantitative assessment of the association of fish and LCn3PUFA intake with diabetes risk and to explore major sources of heterogeneity among studies, we conducted a meta-analysis of all eligible prospective cohort studies with the existing data.