Selenium in ischaemic heart disease.

Ecological between-area comparisons, hospital-based case-control studies and cross-sectional angiography studies have provided data on the role of selenium (Se) deficiency in the aetiology of ischaemic heart disease (IHD), but this evidence is, at best, suggestive because of the potential selection biases and the lack of certainty of the temporal direction of the observed associations. Out of the four cohort-based population studies published so far, one observed a moderate association between a reduced serum Se and an increased risk of IHD and all cardiovascular (CVD) deaths, one was equivocal and two did not find any association between serum Se and IHD. There are, however, several potential sources of biases acting towards the null hypothesis in these studies. In the pooled data of the two separate cohorts from eastern Finland including 377 people who experienced a CVD death or a non-fatal myocardial infarction and equally many event-free risk-factor matched controls, people with serum Se of less than 45 micrograms/l had a 1.7-fold (95% confidence interval 1.2-2.7) risk of an CVD event compared to those with higher serum Se. This association could, however, be explained by the covariation of Se with other nutrients, as for example n-3 polyunsaturated fatty acids. As the evidence concerning the role of serum Se in IHD is inconclusive, we need new epidemiological studies to test the association and experiments exploring the possible mechanisms.