Measurement of zinc absorption from meals: comparison of extrinsic zinc labeling and independent measurements of dietary zinc absorption.
BACKGROUND
Extrinsic labeling techniques are typically used to measure fractional absorption of zinc (FAZ(extrinsic)) but none have been adequately evaluated.


OBJECTIVE
To compare determination of the quantity of zinc absorbed (TAZ(extrinsic)) using measurements of FAZ(extrinsic) with results of simultaneous determinations of dietary zinc absorbed (TAZ(metabolic)) that are not dependent on labeling ingested food with an extrinsic tracer (modified metabolic balance technique).


METHODS
(70)Zn was administered orally with all meals for 6 consecutive days to 21 healthy, free-living adult women consuming a constant diet. (68)Zn and (67)Zn were administered intravenously. FAZ(extrinsic) was measured using a dual isotope tracer ratio technique and multiplied by dietary zinc to give TAZ(extrinsic). TAZ(metabolic) was determined by addition of net absorption of zinc and endogenous fecal zinc, the latter determined by an isotope dilution technique.


RESULTS
TAZ(extrinsic) and TAZ(metabolic) were 3.0 +/- 1.1 mg/day and 3.1 +/- 1.1 mg/day respectively, paired t-test p = 0.492. The correlation coefficient for TAZ(extrinsic) and TAZ(metabolic) was 0.91, and for FAZ(extrinsic) and FAZ(metabolic) was 0.95. A Bland Altman analysis indicated a bias of 0.07, and the limits of agreement of -0.86 to 1.01 for TAZ(extrinsic) and TAZ(metabolic).


CONCLUSIONS
These results from two independent methods provide reasonable validation of our extrinsic labeling technique for a wide range of composite diets.
Sheng
Xiao-Yang
XY
Shanghai Jiao Tong University, School of Medicine, Xin-Hua Hospital, Department of Child and Juvenile Health Care, Shanghai, China.
Hambidge
K Michael
KM
Miller
Leland V
LV
Westcott
Jamie E
JE
Lei
Sian
S
Krebs
Nancy F
NF
D000328:Adult; D015930:Diet Records; D005260:Female; D005502:Food; D006801:Humans; D007408:Intestinal Absorption; D008875:Middle Aged; D015203:Reproducibility of Results; D013194:Staining and Labeling / Q000379:methods*; D055815:Young Adult; D015032:Zinc / Q000493:pharmacokinetics*; D015033:Zinc Isotopes / Q000493:pharmacokinetics*
D015033:Zinc Isotopes; D015032:Zinc