title: Interaction of zinc or vitamin A supplementation and specific parasite infections on Mexican infants' growth: a randomized clinical trial.
abstract: BACKGROUND
  The efficacy of micronutrient supplementation on growth may be modified by specific gastrointestinal parasite infections.
  
  
  METHODS
  We carried out a double-blind placebo-controlled trial to evaluate the effect of vitamin A and zinc supplementation on gastro-intestinal pathogen infections and growth among 584 infants in Mexico City. Children aged 5-15 months were assigned to receive either a vitamin A supplement every 2 months (20,000 IU of retinol for infants < or =; 1 year or 45,000 IU for infants >1 year), a daily supplement of 20 mg of zinc, a combined vitamin A-zinc supplement or a placebo, and were followed up for 1 year. Weight and length were measured once a month and morbidity histories were recorded twice a week for 12 months. Monthly stool samples were screened for Giardia duodenalis, Ascaris lumbricoides and Entamoeba spp. Growth velocity slopes, generated from the linear regression of individual child length, and height-for-age z-scores on time were analyzed as end points in regression models, adjusting for the presence of parasite infections.
  
  
  RESULTS
  The main effect of vitamin A supplementation was in height improvement (P<0.05), and was only found in the model evaluating infants with any parasite. There was an interaction effect of slower growth (P<0.05) found in infants infected with any parasite and supplemented with vitamin A in slower growth (P<0.05). In addition, the interaction of zinc supplementation and Giardia duodenalis or A. lumbricoides was associated with reduced growth (P<0.05).
  
  
  CONCLUSIONS
  Gastro-intestinal parasite infections may modify the effect that zinc or vitamin A supplementation has on childhood growth.
authors.affiliation: School of Natural Sciences, Universidad Autónoma de Querétaro, Mexico. jlrosado@avantel.net
authors.forename: J L
authors.initials: JL
authors.lastname: Rosado
authors.forename: M C
authors.initials: MC
authors.lastname: Caamaño
authors.forename: Y A
authors.initials: YA
authors.lastname: Montoya
authors.forename: M
authors.initials: M
authors.lastname: de Lourdes Solano
authors.forename: J I
authors.initials: JI
authors.lastname: Santos
authors.forename: K Z
authors.initials: KZ
authors.lastname: Long
mesh_terms: D000818:Animals; D001196:Ascariasis / Q000150:complications; D017164:Ascaris lumbricoides; D001827:Body Height / Q000187:drug effects* / Q000502:physiology; D001835:Body Weight / Q000187:drug effects* / Q000502:physiology; D019587:Dietary Supplements; D004404:Dysentery, Amebic / Q000150:complications; D005243:Feces / Q000469:parasitology; D005260:Female; D005873:Giardiasis / Q000150:complications; D006128:Growth / Q000187:drug effects* / Q000502:physiology; D006130:Growth Disorders / Q000209:etiology / Q000517:prevention & control; D006801:Humans; D007223:Infant; D007411:Intestinal Diseases, Parasitic / Q000150:complications*; D008297:Male; D008800:Mexico; D014131:Trace Elements / Q000494:pharmacology; D014801:Vitamin A / Q000494:pharmacology*; D014815:Vitamins / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology*
chemical_list: D014131:Trace Elements; D014815:Vitamins; D014801:Vitamin A; D015032:Zinc