Use of the deuterated-retinol-dilution technique to assess total-body vitamin A stores of adult volunteers consuming different amounts of vitamin A

Abstract

Background: The deuterated-retinol-dilution (DRD) technique provides a quantitative estimate of total body stores of vitamin A. However, it is not known whether the technique can detect changes in vitamin A pool size in response to different intakes of vitamin A. Objective: Our objective was to determine the responsiveness of the DRD technique to 3 different daily supplemental vitamin A intakes during a period of 2.5-4 mo. Design: Two oral doses of [2H4]retinyl acetate [52,4 μmol retinol equivalent (RE)] were administered on study days 1 and 91 to 26 men (18-32 y of age) who were consuming controlled, low-vitamin A diets, and receiving daily either 0, 5.2, or 10.5 μmol RE of unlabeled supplemental retinyl palmitate during a 75- or 129-d period. Plasma isotopic ratios of [2H4]retinol to retinol on day 115 were used to estimate final vitamin A body stores per Furr et al (Am J Clin Nutr 1989;49:713-6). Result: Final (̄ ± SD) estimated vitamin A pool sizes were 0.048 ± 0.031, 0.252 ± 0.045, and 0.489 ± 0.066 mmol in the treatment groups receiving 0, 5.2, and 10.5 μmol RE/d, respectively (P < 0.001). Estimated mean changes in vitamin A pool sizes were similar to those expected for the vitamin A-supplemented groups [estimated:expected (95% CI of change in pool size): 1.08 (0,8, 1.2) and 1.17 (1.0, 1.3)]. Conclusions: The DRD technique can detect changes in total body stores of vitamin A in response to different daily vitamin A supplements. However, abrupt changes in dietary vitamin A intake can affect estimates of total-body vitamin A stores.