According to the results of a study published in the Annals of Internal Medicine, selenium supplementation may have a modest effect on plasma lipids in those with low selenium status. However the clinical relevance of the results is unclear and they should not be used to justify the use of selenium as an additional or alternative therapy for dyslipidaemia.
The authors note that there is conflicting observational evidence that deficiency of selenium is associated with heart disease. Some studies have linked higher selenium status to higher high-density lipoprotein (HDL) cholesterol levels, whereas others have linked it to elevated total or low-density lipoprotein (LDL) cholesterol; others have shown no association. The purpose of the UK PRECISE (United Kingdom PREvention of Cancer by Intervention with SElenium) Pilot Study was to investigate the effects of selenium supplementation on lipid levels, in a larger patient group than those studied previously.
The study randomised 501 volunteers aged 60-74 years across four GP practices in the UK to double-blind treatment with selenium (as high-selenium yeast - SelenoPrecise) at a dose of 100 mcg/d (n=127), 200mcg/d (n=127), or 300mcg/d (n=126), or a yeast-based placebo (n=121) for 6 months. Total and HDL cholesterol concentrations were measured in non-fasting plasma samples of the participants taken at baseline (n=454) and at 6 months (n=394); non-HDL cholesterol levels were calculated. There was no formal power calculation for this pilot study, and the main endpoint was satisfactory recruitment, retention and adherence of volunteers, to ascertain the viability of conducting the main PRECISE trial.
The authors report that the mean plasma selenium concentrations increased in all treatment groups. There were reductions in total cholesterol levels for the 100mcg (placebo-adjusted change of -0.22mmol/L; 95% CI −0.42 to −0.03mmol/L; p=0.02) and 200mcg (−0.25mmol/L; 95% CI −0.44 to −0.07mmol/L; P = 0.008) groups; the decrease in the highest dose group (300mcg daily) was not however statistically significant (−0.07mmol/L; 95% CI −0.26 to 0.12mmol/L; P=0.46). Similar reductions were observed for non-HDL cholesterol levels. For HDL cholesterol, only the difference in the 300mcg dose group was statistically significant (0.06 mmol/L; 95% CI 0.00 to 0.11 mmol/L; P=0.045).
The authors discuss the limitations of their study, noting that the duration of supplementation was short and the age range was limited; in addition this patient sample had a relatively low selenium status. Although the findings were statistically significant, their clinical significance is less clear. The potential role of selenium in cardiovascular disease risk needs to be explored further in large randomised controlled trials in wider populations, and the potential additional risk in other metabolic dimensions needs to be explored.