A Randomized Trial of Selenium Supplementation and Risk of Type-2 Diabetes, as Assessed by Plasma Adiponectin

Randomized, placebo-controlled, double-blind trial in elderly volunteers recruited from four general practices in the United Kingdom, with relatively low baseline selenium status. Participants were aged 60 to 74 years, stratified by age and sex, and enrolled between June 2000 and July 2001.

Participants received oral high-selenium yeast (SelenoPrecise, Pharma Nord) at 100 mg/d, 200 mg/d, or 300 mg/d for a minimum of six months, compared with identical placebo. Treatment was preceded by a four-week placebo run-in, and adherence was assessed by pill count.

Selenium supplementation did not change plasma adiponectin, suggesting no diabetogenic effect in this population. Compared with placebo, adiponectin decreased by 4% with 100 mg/d, 1% with 200 mg/d, and remained unchanged with 300 mg/d; the overall comparison of the three active groups versus placebo was not significant (P = 0.96). Plasma selenium increased significantly and proportionally to dose in the active groups, but no serious adverse events occurred. Twelve adverse events were reported, mainly stomach or abdominal discomfort, and were similarly associated with selenium and placebo.

Per-arm randomized and analyzed sample sizes were not reported in the excerpt, and adiponectin data were incomplete: 473 participants had at least one plasma sample and 340 had both baseline and six-month measurements. Follow-up was only six months, and adiponectin was a surrogate biomarker rather than a clinical diabetes endpoint. The trial also had some withdrawals and adverse event reporting was limited in detail.