Selenium is an essential trace mineral, needed by the body for the production of a number of selenoproteins. It is becoming clear that dietary intakes of selenium in the general population of Northern Europe, Russia, New Zealand, North America and China are marginal, and likely below the level for optimal immune function. Chronic sub-clinical deficiency of selenium manifests itself in an increased cancer incidence because of impaired immune function, but can take decades to develop. According to a Ministry of Agriculture, Food and Fisheries (MAFF) report, average selenium intakes in the United Kingdom are 29 to 39 µg per day. This falls well short of the recommended nutrient intake of 75 µg per day. Consuming 200 µg per day of selenium as yeast has been shown to reduce the chance of developing all types of cancer by 50 %.
To test the benefits of increased intakes of selenium in healthy adults, researchers gave subjects either 50 or 100 µg of selenium as sodium selenite for 15 weeks. The research, published in the American Journal of Clinical Nutrition in 20041, demonstrated that supplementation increased plasma levels of selenium, the selenium pool, as well as lymphocyte glutathione peroxidase activity. In addition, subjects saw an increase in the production of interferon γ and other cytokines, earlier peak T cell proliferation and increased T helper cell number. Roughly halfway through the study, subjects were fed an oral, live attenuated poliomyelitis vaccine. Selenium supplementation of these healthy adult subjects allowed them to more rapidly clear the virus from the body, and less mutation of the virus was detected when the faeces was analysed for poliovirus reverse transcriptase, indicating a better immune response to the viral load.
The authors of the above study concluded that even selenium at the 100 µg per day level did not optimally saturate the subject’s pools of selenium. This is an important finding because many people assume that their multi-vitamin multi-mineral provides adequate selenium to prevent deficiency. However, often the levels of selenium within these supplements are ≤ 100 µg. For example, Solgar VM2000 contains just 25 µg of selenium as selenomethione. Even taking into consideration the United Kingdom average selenium intake from food (reported by MAFF), a person consuming VM2000 would be below the recommended intake of selenium and the level necessary to saturate the selenium pool. Therefore supplementation with 200 µg per day of selenium as yeast, in addition to any other source, is a sensible precaution to take to ensure saturation of the selenium pool.