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Background: Dysprosium is a nonabsorbable rare earth element that has had successful application as a marker for fecal excretion of unabsorbed zinc. Objective: Our goals were 1) to evaluate the efficacy of administering dysprosium with all meals over several days as a method of determining the completeness of fecal collections, 2) to determine the similarity of gastrointestinal transit kinetics and excretion patterns of dysprosium and zinc tracer administered simultaneously over several days, and 3) to evaluate alternative methods of using the data for fecal excretion of orally administered zinc tracer and dysprosium to measure the fractional absorption of zinc. Design: 70Zn and dysprosium were administered orally with all meals for 5 consecutive days to 7 healthy, free-living adults consuming a constant diet based on habitual intake. Additional tracers, 67Zn and 68Zn, were administered intravenously. Urine and fecal samples were collected during tracer administration and for 8 d after the last dose. Isotope ratios were measured in urine and feces, and total zinc and dysprosium were measured in fecal samples. Results: The mean recovery of dysprosium was 101.3 ± 2.4%. The zinc oral tracer and dysprosium had similar fecal excretory patterns; the correlation coefficient for 70Zn and dysprosium in fecal samples exceeded 0.99 (P < 0.0001) for each subject. Fractional zinc absorption measurements using various dysprosium methods correlated well (r > 0.95) with those from the fecal monitoring and dual-isotope-tracer ratio methods. Conclusion: Administration of dysprosium is a useful means of determining the completeness of fecal collections and of measuring zinc absorption. [ABSTRACT FROM AUTHOR]

BACKGROUND: Extrinsic labeling techniques for determining fractional absorption of Zn (FAZ) have never been adequately evaluated. OBJECTIVE: The objective of this study, part of a larger project, was to compare results for determination of FAZextrinsic from a variety of different total diets using our own extrinsic labeling technique with results for simultaneous determination of FAZintrinsic. DESIGN: FAZ was determined for 5 days in 23 adults (Female) while consuming a constant rotating diet based on habitual intake. Zn intake ranged from 5-33mg/d, median 7.6mg/d. For extrinsic labeling, 70Zn tracer was administered gradually during the second half of each meal and absorption determined by our dual isotope tracer ratio (DITR) technique (67Zn infused IV) and by fecal monitoring (FM). FmZintrinsic was calculated from the sum of net absorption of Zn and intestinal excretion of endogenous Zn. RESULTS: Mean ± SD FAZ by DITR, FM and intrinsic were 0.28±0.11, 0.30±0.11 and 0.31±0.15, respectively (ANOVA, p=0.229). CONCLUSION: Small, not statistically significant, differences were found between these 3 methods for determining FAZ. [ABSTRACT FROM AUTHOR]