Human selenium supplementation as assessed by changes in blood selenium concentration and glutathione peroxidase activity.

This review concentrates on the differences in the effects on indicators of selenium (Se) status of different chemical forms proposed for Se supplementation in healthy subjects. Modifications in blood (plasma and erythrocyte) Se concentrations and in the Se-dependent glutathione peroxidase (GSH-Px) enzymatic activity, in plasma, erythrocytes and platelets, were compared considering the basal Se status, the dose and the chemical form of Se supplement, as well as the duration of the intervention. Organic Se forms (Se-yeast, selenomethionine and food-Se) increased blood Se more concentration rapidly and to a greater extent than inorganic forms (selenite and selenate). However, no significant difference in the response of both plasma and erythrocyte GSH-Px activity could be observed. In contrast, platelet GSH-Px activity was more sensitive to the chemical form of Se administered. Saturation of platelet GSH-Px activity occurred at lower plasma Se levels when selenite or selenate were used as Se supplements than with the organic forms. Interpretation of some of the results is provided and ideas are suggested for consideration in further studies.