Haskell, M.J., Ribaya-Mercado, J.D., The Vitamin A Tracer Task Force
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.