The purpose of these guidelines is to assist researchers in designing and carrying out studies using the stable isotope dilution technique to assess the efficacy and effectiveness of vitamin A interventions aimed at improving vitamin A status in populations at risk of deficiency. Although other stable and radiolabeled isotopic techniques are available for studying vitamin A and carotenoid metabolism, these guidelines focus on the stable isotope dilution technique for assessment of vitamin A status. This technique has been validated against liver vitamin A concentrations in surgical patients with low to adequate liver vitamin A stores. Results of those studies indicate that the technique provides an accurate quantitative estimate of mean total body vitamin A pool size for groups of subjects. It is important to note that the technique does not provide precise estimates of vitamin A pool size for individual subjects, and hence it is not intended for use as a diagnostic method for assessing vitamin A status in individuals.
HarvestPlus Technical Monograph 5. 27 pp.