Biokinetic studies in humans with stable isotopes as tracers. Part 2: Uptake of molybdenum from aqueous solutions and labelled foodstuffs

Molybdenum (Mo) has been identified as an essential trace metal for humans. The present study was aimed at the assessment of data on intestinal Mo absorption from aqueous solutions and from foodstuffs in humans applying the methodology for instrinsic labelling described in Part 1. The intestinal absorption of Mo was investigated by means of a double tracer method in 3 healthy volunteers on a total of 15 occasions. When administered as aqueous solution, almost complete uptake of Mo was observed up to doses of 1 mg and only a slight decrease for higher doses. But addition of black tea reduces the absorbed fraction by about a factor of ten. Studying Mo absorption from food, intrinsically labelled cress showed a reduced uptake as compared to extrinsically labelled cress and aqueous solutions. Even less Mo was absorbed from an extrinsically labelled composite meal. The data obtained demonstrate a pattern of intestinal Mo absorption which is different from that of other essential trace metals, e.g., Fe or Co.