Bioavailability of zinc from a diet based on isolated soy protein: Application in young men of the stable isotope tracer, Zn-70

Combined extrinsic labeling of meals and fecal monitoring of zinc (Zn) excretion was done using the stable, safe Zn isotope, Zn-70, for assessing the effects of vegetable (soy) and animal (milk, beef) protein on Zn absorption in healthy, adult humans. Known amounts of Zn-70 (as Zn chloride) were added to 6 consecutive meals over a 2-day period, during which 1 of 3 osonitrogenous liquid formulas (skim milk, soy isolate, or a 1:1 mixture) or 1 of 2 bologna sausages (soy isolate or beef) were given. Mean absorption of Zn-70 from milk, soy and soy-milk mixture was 41, 34, and 41% respectively. Isotope excretion kinetics, stool sample pooling procedures, and use of fecal markers were also evaluated. The results suggested that the presence of soy protein had no effect on Zn-70 absorption, while beef may favor Zn absorption relative to soy. (wz)