This small human study measured selenium intake and urinary and fecal losses in four women eating their usual diets, and combined these with radioactive selenium tracers given as selenomethionine or selenite. About four fifths of food selenium was absorbed. Whole-body selenium estimates were roughly twice as high when based on selenomethionine as when based on selenite, and the authors suggest the minimum requirement is probably not more than 20 µg per day.
Key numbers
- Mean dietary selenium over 14 days: 24.2 µg/day; urinary 13.1 µg/day; fecal 10.8 µg/day; balance +0.3 µg/day (n = 4) (Abstract, p. 45).
- Intestinal absorption of food selenium: 0.76 to 0.83 of intake, mean 0.79 (Abstract, p. 45).
- Whole-body selenium from selenomethionine data: means of 6.9, 5.2 and 6.2 mg by three methods; from selenite data: means of 2.9, 3.5 and 2.6 mg (Abstract, p. 45).
- Authors’ inference: minimum requirement probably not more than 20 µg/day (Abstract, p. 45).
Methods (brief)
Measurements were made during earlier tracer studies of selenium-75 labeled selenomethionine and selenite in young women. Stable selenium in diet, urine, feces and plasma was measured fluorimetrically, and whole-body selenium was calculated three ways from tracer kinetics.
Evidence fitness
Supports evidence that food selenium is well absorbed and that the chemical form given (selenomethionine versus selenite) changes apparent body retention. It cannot set population requirements or upper limits on its own.
Limitations
Four subjects; tracer studies done in different years; requirement inference is the authors’ interpretation of a small low-intake group.
Related evidence
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