title: International experiences in assessing vitamin A status and applying the vitamin A-labeled isotope dilution method.
abstract: Inadequate vitamin A (VA) nutrition continues to be a major problem worldwide, and many interventions being implemented to improve VA status in various populations need to be evaluated. The interpretation of results after an intervention depends greatly on the method selected to assess VA status. To evaluate the effect of an intervention on VA status, researchers in Cameroon, India, Indonesia, Mexico, Senegal and Zambia have used serum retinol as an indicator, and have not always found improvement in response to supplementation. One problem is that homeostatic control of serum retinol may mask positive effects of treatment in that changes in concentration are observed only when status is either moderately to severely depleted or excessive. Because VA is stored mainly in the liver, measurements of hepatic VA stores are the gold standard for assessing VA status. Dose response tests such as the relative dose response (RDR) and the modified relative dose response (MRDR), allow a qualitative assessment of VA liver stores. On the other hand, the use of the vitamin A-labeled isotope dilution (VALID) technique, (using 13C or 2H-labeled retinyl acetate) serves as an indirect method to quantitatively estimate total body and liver VA stores. Countries including Cameroon, China, Ghana, Mexico, Thailand and Zambia are now applying the VALID method to sensitively assess changes in VA status during interventions, or to estimate a populations dietary requirement for VA. Transition to the use of more sensitive biochemical indicators of VA status such as the VALID technique is needed to effectively assess interventions in populations where mild to moderate VA deficiency is more prevalent than severe deficiency.
authors.affiliation: Nutritional Sciences, Department of Biological and Chemical Sciences, Universidad de Sonora, Hermosillo, Mexico; Research Center for Food and Development, Sonora, Mexico.
authors.forename: Veronica
authors.initials: V
authors.lastname: Lopez-Teros
authors.affiliation: Tropical Diseases Research Centre, Ndola Central Hospital, Ndola, Zambia.
authors.forename: Justin
authors.initials: J
authors.lastname: Chileshe
authors.affiliation: Laboratoire de Nutrition, Département de Biologie Animale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar (UCAD), Dakar, Senegal.
authors.forename: Nicole
authors.initials: N
authors.lastname: Idohou-Dossou
authors.affiliation: Center for Applied Health Technology and Clinical Epidemiology, National Institute of Health Research and Development (NIHRD) Ministry of Health, Bogor, Indonesia.
authors.forename: Tetra
authors.initials: T
authors.lastname: Fajarwati
authors.affiliation: Centre for Food and Nutrition Research, IMPM (Institut de recherches medicales et detudes des plantes medicinales), Yaoundé, Cameroon.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Medoua Nama
authors.affiliation: Kintampo Health Research Centre, Kintampo, Ghana.
authors.forename: Sam
authors.initials: S
authors.lastname: Newton
authors.affiliation: Sundar Serendipity Foundation, Chennai, India.
authors.forename: Malavika
authors.initials: M
authors.lastname: Vinod Kumar
authors.affiliation: Department of Nutrition, School of Public Health, Nanjing Medical University, Nanjing, Jiangsu, PR China.
authors.forename: Zhixu
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Institute of Nutrition, Mahidol University, Nakhon Pathom, Thailand.
authors.forename: Emorn
authors.initials: E
authors.lastname: Wasantwisut
authors.affiliation: Nutritional and Health-Related Environmental Studies Section, Division of Human Health, IAEA, Vienna, Austria.
authors.forename: Janet R
authors.initials: JR
authors.lastname: Hunt
mesh_terms: D006801:Humans; D007201:Indicator Dilution Techniques; D007553:Isotope Labeling; D008099:Liver / Q000378:metabolism; D009752:Nutritional Status; D014801:Vitamin A / Q000378:metabolism*; D014802:Vitamin A Deficiency / Q000453:epidemiology
chemical_list: D014801:Vitamin A
keywords: Cameroon; China; Ghana; India; Indonesia; Mexico; Senegal; Thailand; Vitamin A status; Zambia; children; labeled retinol; lactating women; stable isotope dilution