Quantitative assessment of total body stores of vitamin A in adults with the use of a 3-d deuterated-retinol-dilution procedure

Background: The conventional deuterated-retinol-dilution (DRD) technique provides a quantitative estimate of total body stores of vitamin A in humans. The procedure requires equilibration of serum deuterated retinol with nondeuterated retinol after administration of an oral dose of deuterated vitamin A. Equilibration takes approximate to3 wk to complete. Objective: Our goal was to develop a predictive mathematical formula for quantitative assessment of total body stores of vitamin A in adults by using a procedure that takes less time to perform because serum isotope equilibration is not required, so that blood drawing can be done 3 d, instead of approximate to3 wk, after isotope dosing. Design: Ratios of serum deuterated to nondeuterated retinol (D:H retinol) were determined in Filipino adults (n = 68) 3 and 20 d after an oral dose of 0.015 mmol [H-2(4)]retinyl acetate and in Guatemalan adults (n = 15) 3 and 21 d after a 0.030-mmol dose. D:H retinol values 20 or 21 d after the isotope dose were used in a mathematical formula to obtain quantitative estimates of total body stores of vitamin A that were then correlated with serum D:H retinol values 3 d after the isotope dose. Results: The relation between these variables was nonlinear and was described by the following equation: total body stores of vitamin A (in mmol retinol) = 0.00468 x 10(37(isotope) (dose) (in) (mmol))/D:H retinol in serum 3 d after the isotope dose. Conclusion: A 3-d DRD technique could be used for quantitative assessment of total body stores of vitamin A; this technique takes less time than does the conventional DRD technique.