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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]