CAN A DOUBLE ISOTOPE METHOD BE USED TO MEASURE FRACTIONAL ZINC-ABSORPTION FROM URINARY SAMPLES

Objective: This study was designed to test whether fractional absorpti on calculated from urinary enrichment of stable isotopes of zinc accur ately 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 zin c. They attended the local hospital for isotope administration. Subjec ts: Fifteen volunteers were recruited, seven of whom had non-insulin d ependent diabetes mellitus. All completed the study, but five did not carry out a complete faecal collection. Interventions: Each subject re ceived an oral and i.v. dose of different stable isotopes of zinc with breakfast. Faecal and urinary enrichment with the isotopes was measur ed. Results: There was no significant correlation between the two meas ures of absorption. Conclusions: The double label stable isotope techn ique for determining zinc absorption from measurements of urinary enri chment does not reliably predict true zinc absorption (measured by fae cal and urinary monitoring) in a heterogenous group of adults given re latively low doses of stable isotopes of zinc.