The use of high-selenium yeast to raise selenium status: how does it measure up?

Abstract

Selenium-enriched yeast (Se-yeast) is a common form of Se used to supplement the dietary intake of this important trace mineral. However, its availability within the European Union is under threat, owing to concerns expressed by the European Community (EC) Scientific Committee on Food that Se-yeast supplements are poorly characterised and could potentially cause the build up of Se in tissues to toxic levels. The present review examines the validity of these concerns. Diagrams of the biosynthesis and metabolism of Se compounds show which species can be expected to occur in Se-yeast preparations. Se-yeast manufacture is described together with quality-control measures applied by reputable manufacturers. The way in which speciation of Se-yeast is achieved is explained and results on amounts of Se species in various commercial products are tabulated. In all cases described, selenomethionine is the largest single species, accounting for 54 -74 % of total Se. Se-yeast is capable of increasing the activity of the selenoenzymes and its bioavailability has been found to be higher than that of inorganic Se sources in all but one study. Intervention studies with Se-yeast have shown the benefit of this form in cancer prevention, on the immune response and on HIV infection. Of about one dozen supplementation studies, none has shown evidence of toxicity even up to an intake level of 800 mg Se/d over a period of years. It is concluded that Se-yeast from reputable manufacturers is adequately characterised, of reproducible quality, and that there is no evidence of toxicity even at levels far above the EC tolerable upper intake level of 300 mg/d.

The role of organic selenium in cadmium toxicity: effects on broiler performance and health status

“…The antioxidant role of Se was affirmed as it partially protected against Cd contamination. Selenomethionine, a major constituent of Se-yeast, is non-specifically incorporated into proteins in place of methionine (Rayman, 2004), and it is believed that stored tissue Se levels can be mobilized and used in circumstances of oxidative stress. In a previous study In T1 treatment, broilers were fed a diet with 0.3 mg/kg added Se, as Se-yeast, without added Cd; in T2, broilers were fed a diet with 0.3 mg/kg Se and 10 mg/kg Cd; in T3, broilers were fed a diet with 0.3 mg/kg Se and 100 mg/kg of Cd; and in T4 treatment broilers were fed a diet with 3 mg/kg Se and 100 mg/kg Cd.…”

Dietary manipulation in musculoskeletal conditions

“…• Recommended daily intakes (average 53µg/d for women and 60µg/d for men) are not currently achieved in the majority of European countries together with parts of China [83].…”

Selenium persistency and speciation in the tissues of lambs following the withdrawal of dietary high-dose selenium-enriched yeast

“…Speciation of Se fractions showed that much of the large difference in total blood Se concentrations in HSY animals was due to the greater proportion of total Se comprised as SeMet, probably attributable to a combination of the high concentration of SeMet in the SY product (SeMet comprises 54 to 74% of total Se; Rayman, 2004) and the uptake of SeMet from the gastro-intestinal tract via Methionine transporter mechanisms (Weiss, 2003) during the period of supplementation. Furthermore, decreases seen in whole-blood total Se between successive time points was primarily the result of decreases in the proportion of total Se comprised as SeMet, because the proportion of total Se comprised as SeCys was similar between both treatment groups and sequential time points.…”