Can a double isotope method be used to measure fractional zinc absorption from urinary samples?

Abstract

Objective: This study was designed to test whether fractional absorption calculated from urinary enrichment of stable isotopes of zinc accurately reflects true absorption measured by faecal monitoring.

Design: The two techniques were directly compared in volunteers, whereby each subject acted as his/her own control.

Setting: Volunteers were healthy adults, living at home, who were taking part in a larger study on zinc. They attended the local hospital for isotope administration.

Subjects: Fifteen volunteers were recruited, seven of whom had non-insulin dependent diabetes mellitus. All completed the study, but five did not carry out a complete faecal collection.

Interventions: Each subject received an oral and i.v. dose of different stable isotopes of zinc with breakfast. Faecal and urinary enrichment with the isotopes was measured.

Results: There was no significant correlation between the two measures of absorption.

Conclusions: The double label stable isotope technique for determining zinc absorption from measurements of urinary enrichment does not reliably predict true zinc absorption (measured by faecal and urinary monitoring) in a heterogenous group of adults given relatively low doses of stable isotopes of zinc.

Sponsorship: This work was funded by the European Commission (Training and Mobility Programme).