Assessment of total body stores of vitamin A in Guatemalan elderly by the deuterated-retinol-dilution method

Background: Deuterated retinol dilution (DRD) gives quantitative estimates of total body stores of vitamin A. Objectives: In elderly people, we studied 1) the time when an oral dose of deuterated vitamin A equilibrates with body stores, 2) whether serum ratios of deuterated to nondeuterated retinol (D:H) at 3 or 6 d postdosing predic ted body stores, and 3) the ability of DRD to detect changes in the size of the body vitamin A pool. Design: A 10-mg oral dose of [H-2(4)]retinyl acetate was administered to 60 -81-y-old Guatemalans (n = 47); percentage enrichment of serum retinol with deuterated retinol was determined at 1-3 time points per subject at 3, 6, 7, 14, 20, 21, and 54 d. In subjects from whom blood was obtained at 3 and 21 d (n = 15) and at 6 and 20 d (n = 9), total body stores were calculated by using the formula of Furr et al (Am J Clin Nutr 1989;49:713-6) with 21- or 20-d data and correlated with serum D:H at 3 or 6 d postdosing. Nine sub jects received diets containing 982 +/- 20 mu g RE ((x) over bar +/- SEM) p lus 800 mu g RE as retinyl acetate supplements for 32 d. DRD, serum retinol , and relative dose response were used to assess vitamin A status before an d after the intervention. Results: Deuterated retinol equilibrated with the body pool by 20 d postdos ing, Vitamin A supplementation for 32 d increased body stores, although une xplained exaggerated increases were seen in some subjects. An inverse linea r relation was found between estimates of body stores and serum D:H at 3 d postdosing (r = -0.75, P = 0.002); at 6 d postdosing, the correlation was w eaker. Conclusions: DRD can detect changes in total body stores of vitamin A, alth ough factors affecting serum D:H need to be elucidated. Serum D:H 3 d postd osing might be used as an early indicator of total body stores of vitamin A , although a predictive equation will need to be developed.