title: Iron and zinc supplementation improves indicators of vitamin A status of Mexican preschoolers.
abstract: BACKGROUND
  The coexistence of multiple micronutrient deficiencies is a widespread public health problem in many regions of the world. Interactions between zinc deficiency and vitamin A metabolism have been reported but no longitudinal studies have evaluated the effect of iron deficiency on vitamin A.
  
  
  OBJECTIVE
  The objective of this study was to investigate the effect of supplementation with iron, zinc, or both on vitamin A and its metabolically related proteins retinol binding protein (RBP) and transthyretin.
  
  
  METHODS
  The study was a longitudinal, double-blind, placebo-controlled trial in which 219 rural Mexican children aged 18-36 mo were randomly assigned to receive 20 mg Zn/d, 20 mg Fe/d, 20 mg Zn/d plus 20 mg Fe/d, or placebo.
  
  
  RESULTS
  Six months after supplementation, plasma retinol increased in all supplemented groups. Compared with placebo, zinc supplementation was associated with significantly higher plasma retinol and transthyretin but the increase in RBP was not significant. Iron supplementation significantly increased plasma retinol, RBP, and transthyretin. Supplementation with zinc plus iron significantly increased plasma retinol but not RBP or transthyretin. Children deficient in zinc, iron, or vitamin A (as indicated by nutrient plasma concentration) at the beginning of the study had a significantly greater increase in retinol than did children with adequate nutrient status.
  
  
  CONCLUSIONS
  Supplementation with zinc, iron, or both improved indicators of vitamin A status. The results of this study agree with previous observations of a metabolic interaction between zinc and vitamin A and suggest an interaction between iron and vitamin A metabolism.
authors.affiliation: Department of Nutritional Physiology, National Institute of Nutrition, Mexico City, Mexico.
authors.forename: E C
authors.initials: EC
authors.lastname: Muñoz
authors.forename: J L
authors.initials: JL
authors.lastname: Rosado
authors.forename: P
authors.initials: P
authors.lastname: López
authors.forename: H C
authors.initials: HC
authors.lastname: Furr
authors.forename: L H
authors.initials: LH
authors.lastname: Allen
mesh_terms: D002675:Child, Preschool; D019587:Dietary Supplements; D004311:Double-Blind Method; D005293:Ferritins / Q000097:blood; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007223:Infant; D007501:Iron / Q000097:blood; D000090463:Iron Deficiencies; D019266:Iron, Dietary / Q000008:administration & dosage*; D008137:Longitudinal Studies; D008800:Mexico; D009752:Nutritional Status; D010919:Placebos; D011228:Prealbumin / Q000032:analysis; D014801:Vitamin A / Q000097:blood*; D015032:Zinc / Q000008:administration & dosage* / Q000097:blood / Q000172:deficiency
chemical_list: D006454:Hemoglobins; D019266:Iron, Dietary; D010919:Placebos; D011228:Prealbumin; D014801:Vitamin A; D005293:Ferritins; D007501:Iron; D015032:Zinc