Response of Selenium Status Indicators to Supplementation of Healthy North American Men with High-Selenium Yeast

Abstract

The essential nutrient selenium is required in microgram amounts [recommended dietary allowance (RDA) = 55 microg/day, 699 nmol/day] and has a narrow margin of safety (upper tolerable intake limit = 400 microg/day, 5 micromol/day). We conducted a randomized placebo-controlled study of high-selenium yeast, the form used in most supplements (300 microg/day, 3.8 micromol/day), administered to 42 free-living healthy men for 48 weeks. Dietary intakes of selenium, macronutrients, and micronutrients were not different between groups and did not change during the study. Supplementation more than doubled urinary selenium excretion from 69 to 160 microg/day (876 to 2,032 nmol/day). Urinary excretion was correlated with recent selenium intake estimated from 3-day diet records: urinary selenium excretion = 42 microg/day (533 nmol/day) + 0.132 x dietary selenium intake, p < 0.001. Dietary selenium intake was not significantly correlated with the other indicators of selenium status, presumably because urinary selenium excretion reflected recent intake, and tissue selenium was homeostatically controlled. After 48 weeks of supplementation, plasma selenium was increased 60% from 142 to 228 microg/l (1.8 to 2.9 micromol/l), and erythrocyte selenium was approximately doubled from 261 to 524 microg/l (3.3 to 6.6 micromol/l). Selenium concentrations increased more modestly in hair (56%) and platelets (42%). Platelets were the only blood component in which glutathione peroxidase activity was significantly related to selenium content. Selenium levels decreased rapidly after the end of supplementation, and there were no significant differences in selenium status indicators between groups by week 96. The absorption, distribution, and excretion of selenium from high-Se yeast were similar to selenium in foods.

Antioxidant Activity of Sulfur and Selenium: A Review of Reactive Oxygen Species Scavenging, Glutathione Peroxidase, and Metal-Binding Antioxidant Mechanisms

“…The body contains complex antioxidant systems that require adequate intake of selenium for normal physiological function; the RDA for selenium is approximately 55 lg/day and selenium can be incorporated into the body by ingesting foods such as carrots, cabbage, garlic, mushrooms, cheese, meats, and grains and selenium-containing supplements [186][187][188]. Selenium, in the form of selenocysteine, is a constituent of 25 classes of selenoproteins, including GPxs, selenoproteins P, W, and R, and thioredoxins [189][190][191].…”

Bioavailability Comparison of Nine Bioselenocompounds In Vitro and In Vivo

“…Se is an essential element in animals but can be very toxic when the amount ingested exceeds the nutritional intake level. In addition, the adequate physiological range between deficient and excess doses is narrow [4], being one order of magnitude (0.1–1.0 μg/g diet or mL drinking water) in experimental animals. Generally, inorganic Se species, such as selenite, are more toxic than organic Se species, such as selenomethionine (SeMet), and naturally occurring Se compounds, such as animal and plant metabolites, are less toxic than artificial Se compounds.…”

Selenium supplementation does not improve vascular responsiveness in healthy North American men

“…The present study was part of a broader investigation into the health effects of long-term, high-level Se supplementation in healthy men aged 18 -45 yr. Only the results pertaining to brachial artery responsiveness and cardiovascular markers in serum are presented here. Other aspects of the main study have been reported elsewhere (32,34). Potential volunteers were examined by a nurse practitioner and determined to be in good health.…”