Zinc absorption in women: comparison of intrinsic and extrinsic stable-isotope labels
1991
Egan, C.B. | Smith, F.G. | Houk, R.S. | Serfass, R.E.
Fractional absorption of extrinsic and intrinsic zinc from milk-based formulated diets was measured in 10 young women by using a simultaneous triple-isotope method based on fecal monitoring of unabsorbed enriched stable-isotope labels. Zinc intake was held nearly constant (average zinc intake = 1.48 micromole.kg body wt-1.d-1) throughout the 18-d controlled feeding phase of the study by addition of extrinsic 64Zn to all formula feedings, with substitution of the extrinsic 67Zn label for some of the 64Zn when formula intrinsically labeled with 70Zn was given. Fractional absorption values of intrinsic and extrinsic zinc labels, 0.267 +/- 0.092 (average +/- SD) and 0.282 +/- 0.086, respectively, were highly correlated (r = 0.83, P < 0.05) and did not differ significantly. The ratio of fractional absorption of the extrinsic to that of the intrinsic label, 1.08 +/- 0.20 (average +/- SD), was not significantly different from unity. The results show that extrinsic labeling by use of enriched stable isotopes is a valid means of determining zinc absorption from milk-based diets in adult humans.
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