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

Abstract

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. The two techniques were directly compared in volunteers, whereby each subject acted as his/her own control. 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. 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. 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. There was no significant correlation between the two measures of absorption. 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.