Use of Theoretical Subjects to Develop a Method for Assessing Equivalence of Dietary Vitamin A in a Mixed Diet

Tsitsi Chimhashu; Michael H Green; Joanne Balmer Green; Alida Melse-Boonstra

doi:10.1016/j.tjnut.2023.06.034

Use of Theoretical Subjects to Develop a Method for Assessing Equivalence of Dietary Vitamin A in a Mixed Diet

J Nutr. 2023 Aug;153(8):2523-2530. doi: 10.1016/j.tjnut.2023.06.034. Epub 2023 Jun 26.

Authors

Tsitsi Chimhashu¹, Michael H Green², Joanne Balmer Green², Alida Melse-Boonstra³

Affiliations

¹ Division of Human Nutrition and Health, Wageningen University & Research, Wageningen, The Netherlands; Centre of Excellence for Nutrition, North-West University, Potchefstroom, South Africa.
² Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA, United States.
³ Division of Human Nutrition and Health, Wageningen University & Research, Wageningen, The Netherlands. Electronic address: alida.melse@wur.nl.

PMID: 37380059
DOI: 10.1016/j.tjnut.2023.06.034

Abstract

Background: Although the vitamin A (VA) equivalency of provitamin A carotenoids from single foods or capsules has been studied using several approaches, there is currently no reliable method to determine VA equivalency for mixed diets.

Objectives: To reach the objective of identifying a method to determine the VA equivalency of provitamin A carotenoids in mixed diets, we tested a new approach using preformed VA as proxy for provitamin A.

Methods: We studied 6 theoretical subjects who were assigned physiologically plausible values for dietary VA intake, retinol kinetic parameters, plasma retinol pool size, and VA total body stores. Using features in the Simulation, Analysis and Modeling software, we specified that subjects ingested a tracer dose of stable isotope-labeled VA on day 0 followed by 0-μg supplemental VA or 200, 400, 800, 1200, 1600, and 2000 μg VA daily from day 14 to day 28; we assigned VA absorption to be 75%. For each supplement level, we simulated plasma retinol specific activity (SA_p) over time and calculated the mean decrease in SA_p relative to 0 μg. Group mean data were fitted to a regression equation to calculate predicted VA equivalency at each supplement level on day 28.

Results: For each subject, higher VA supplement loads resulted in lower SA_p, with the magnitude of the decrease differing among subjects. The mean predicted amount of absorbed VA was within 25% of individual subjects' assigned amount for 4 of the 6 subjects, and the mean ratio of predicted to assigned amount of absorbed VA over all supplement loads ranged from 0.60 to 1.50, with an overall mean ratio of 1.0.

Conclusions: Results for preformed VA suggest that this protocol may be useful for determining VA equivalency of provitamin A carotenoids in free-living subjects if mixed diets with known provitamin A content were substituted for the VA supplements.

Keywords: model-based compartmental analysis; provitamin A carotenoids; specific activity of retinol in plasma; stable isotope dilution technique; vitamin A; vitamin A equivalency.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Carotenoids
Diet
Dietary Supplements / analysis
Humans
Provitamins / analysis
Vitamin A Deficiency* / prevention & control
Vitamin A*

Substances

Vitamin A
Provitamins
Carotenoids