A prospective study of dietary selenium intake and risk of type 2 diabetes

Background: Growing evidence raises concern about possible associations of high selenium exposure with diabetes in selenium-replete populations such as the US. In countries with lower selenium status, such as Italy, there is little epidemiological evidence on the association between selenium and diabetes. This study examined the prospective association between dietary selenium intake and risk of type 2 diabetes. Methods: The ORDET cohort study comprised a large sample of women from Northern Italy (n = 7,182). Incident type 2 diabetes was defined as a self-report of a physician diagnosis, use of antidiabetic medication, or a hospitalization discharge. Dietary selenium intake was measured by a semi-quantitative food-frequency questionnaire at the baseline examination (1987-1992). Participants were divided in quintiles based on their baseline dietary selenium intake. Results: Average selenium intake at baseline was 55.7 mu g/day. After a median follow-up of 16 years, 253 women developed diabetes. In multivariate logistic regression analyses, the odds ratio for diabetes comparing the highest to the lowest quintile of selenium intake was 2.39, (95% CI: 1.32, 4.32; P for linear trend = 0.005). The odds ratio for diabetes associated with a 10 mu g/d increase in selenium intake was 1.29 (95% CI: 1.10, 1.52). Conclusions: In this population, increased dietary selenium intake was associated with an increased risk of type 2 diabetes. These findings raise additional concerns about the association of selenium intake above the Recommended Dietary Allowance (55 mu g/day) with diabetes risk.