IHN Database

RDA for selenium may need revision

BEIJING, CHINA. Deficiency of the micronutrient selenium is common in many developing countries. Selenium is of fundamental importance to human health, as it is an essential component of several major metabolic pathways, including thyroid hormone metabolism, antioxidant defence systems, and immune function. An intake consistently below the recommended dietary allowance (RDA) for adults of 55 micrograms per day could therefore have several potential public health implications.

Researchers from the Chinese Academy of Preventive Medicine measured the effects of selenium supplementation in two forms: selenite, an inorganic salt, and selenomethionine, an organic form of selenium. Selenomethionine is the major form of selenium found in food. They recruited 120 men and women in China who were deficient in selenium, and monitored their selenium status by measuring plasma levels of glutathione peroxidase and selenoprotein P. Before the study, the participants had an average selenium intake of 10 mcg per day. They were randomized and given supplements for 20 weeks at various doses from zero to 66 mcg per day, or placebo. Results showed that optimum levels of glutathione peroxidase were reached with 37 mcg when given as selenomethionine, and with 66 mcg as selenite. However, optimum levels of selenoprotein P were not reached at all, leading the researchers to conclude that this is a better indicator of selenium nutritional status. Optimization of selenoprotein P would require either a longer period of supplementation or higher doses, they suggest. They also point out that the RDA was set based on studies using glutathione peroxidase, so propose that the recommendation should be revised on the basis of selenoprotein P. Regarding the form of supplementation, the study demonstrates that selenomethionine has nearly double the bioavailability of selenite and is thus superior for increasing selenium status. This work supports previous studies which have demonstrated superior absorption rates with selenomethionine as compared to selenite.
Xia, Y et al. Effectiveness of selenium supplements in a low-selenium area of China. American Journal of Clinical Nutrition, Vol. 81, April 2005, pp. 829-834

category search
Keyword Search

copyright notice