TY - JOUR
T1 - Retinol isotope dilution is applied during restriction of vitamin a intake to predict individual subject total body vitamin a stores at isotopic equilibrium
AU - Green, Michael H.
AU - Ford, Jennifer Lynn
AU - Green, Joanne Balmer
N1 - Publisher Copyright:
© 2016 American Society for Nutrition.
PY - 2016
Y1 - 2016
N2 - Background: Retinol isotope dilution (RID) equations are used to determine vitamin A status and the efficacy of vitamin A intervention programs. Recent work related to RID methods has focused on modifying the ''Olson equation'' to improve the accuracy of predictions of vitamin A total body stores (TBS) in individual subjects. Objective: We investigated the hypothesis that short-term restriction of vitamin A intake would result in accurate RID prediction of vitamin A TBS in individuals. Methods: We applied model-based compartmental analysis to a 6-component model derived from published retinol kinetic studies on 12 individuals with a wide range of vitamin A stores and determined vitamin A TBS in the steady state. Then we simulated the impact of eliminating or strictly limiting vitamin A intake at the time of isotope administration, while maintaining plasma retinol homeostasis, on retinol specific activity in plasma (SAp; fraction of dose/mmol retinol) and stores, and we calculated TBS using the simplified RID equation TBS = 0.75 3 1/SAp, where the fractional absorption of tracer was set at 0.75 and SAp was simulated 5 d after dosing. Results: When vitamin A intake was zero or strictly limited (0.25 mmol/d), mean TBS predicted by the equation at 5 d after dose administration divided by TBS determined by using the model was 1.00 (range: 0.959-1.04) or 1.02 (range: 0.983 - 1.06), respectively. Conclusions: By eliminating or strictly limiting vitamin A input, isotopic equilibrium was reached by 5 d. At isotopic equilibrium, SAp is the same as that in the body's exchangeable vitamin A pools; under these conditions, SAp may be measured at any time from 5 d on and used to calculate TBS.
AB - Background: Retinol isotope dilution (RID) equations are used to determine vitamin A status and the efficacy of vitamin A intervention programs. Recent work related to RID methods has focused on modifying the ''Olson equation'' to improve the accuracy of predictions of vitamin A total body stores (TBS) in individual subjects. Objective: We investigated the hypothesis that short-term restriction of vitamin A intake would result in accurate RID prediction of vitamin A TBS in individuals. Methods: We applied model-based compartmental analysis to a 6-component model derived from published retinol kinetic studies on 12 individuals with a wide range of vitamin A stores and determined vitamin A TBS in the steady state. Then we simulated the impact of eliminating or strictly limiting vitamin A intake at the time of isotope administration, while maintaining plasma retinol homeostasis, on retinol specific activity in plasma (SAp; fraction of dose/mmol retinol) and stores, and we calculated TBS using the simplified RID equation TBS = 0.75 3 1/SAp, where the fractional absorption of tracer was set at 0.75 and SAp was simulated 5 d after dosing. Results: When vitamin A intake was zero or strictly limited (0.25 mmol/d), mean TBS predicted by the equation at 5 d after dose administration divided by TBS determined by using the model was 1.00 (range: 0.959-1.04) or 1.02 (range: 0.983 - 1.06), respectively. Conclusions: By eliminating or strictly limiting vitamin A input, isotopic equilibrium was reached by 5 d. At isotopic equilibrium, SAp is the same as that in the body's exchangeable vitamin A pools; under these conditions, SAp may be measured at any time from 5 d on and used to calculate TBS.
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U2 - 10.3945/jn.116.238899
DO - 10.3945/jn.116.238899
M3 - Article
C2 - 27683870
AN - SCOPUS:84995487913
VL - 146
SP - 2407
EP - 2411
JO - Journal of Nutrition
JF - Journal of Nutrition
SN - 0022-3166
IS - 11
ER -