Scientific rationale for the 1989 recommended dietary allowance for selenium.

During the past 15 years, our knowledge of human selenium requirements has improved greatly, primarily because of research conducted in the People's Republic of China. Dietary surveys demonstrated that Keshan disease, a juvenile cardiomyopathy, was absent in parts of China where the food supply provided at least 19 and 13 micrograms selenium per day for men and women, respectively. Such intakes can be regarded as minimum daily requirements for selenium. Chinese scientists also carried out a study in an area where Keshan disease was prevalent to determine the amount of dietary selenium needed to maximize the activity of the selenium-containing enzyme, glutathione peroxidase, in plasma. For a man weighing 60 kg, enzymatic activity reached a plateau at selenium intakes of about 40 micrograms per day. These data were used by the US National Research Council as the basis for its 1989 Recommended Dietary Allowance (RDA) for selenium. The RDA was calculated as 70 and 55 micrograms per day for adult men and women, respectively, after correcting for differences in body size and taking into consideration possible individual variations in requirements. This RDA is readily satisfied by typical diets in countries with relatively selenium-rich soils, such as the United States. In selenium-poor areas of the world (eg, China, New Zealand, Scandinavia), diets would not readily furnish such intakes.