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Objective: To explore the effect of vitamin A supplements on iron metabolic homeostasis for preschoolers.Method:In this randomized, placebo-controlled and blinded field intervention trial, about 445 3-6 years old preschoolers were randomly selected from all eight kindergartens in the area.All subjects were randomly divided into four groups: sole vitamin A supplementation group (Group Ⅰ, a single oral dose of vitamin A about 200,000 units), sole iron supplement group (Group Ⅱ, daily oral supplement with the element iron 1-2 mg/kg/day for five days a week, lasting for 6 months) and the combined supplement of vitamin A and iron (Group Ⅲ)and administration no vitamin A and ferrous sulfate as placebo-control (Group Ⅳ).The concentration of serum vitamin A was measured by high-performance liquid chromatography (HPLC), serum ferritin (SF) by enzyme-linked immunosorbent assay (ELISA), serum transferring receptor (sTfR) by microparticle-enhanced immunoassay, C-reactive protein (CRP) by particle-enhanced immunoturbidimetry and hemoglobin (HB) by hemiglobincyanide and sTfR-SF index (TFR-F index) and total body iron content (TBIC) were computed before and after intervention, respectively.Simultaneously, childrens demographic data,socio-economic status and eating habits, etc were investigated by questionnaires.Result: A total of 387 (95, 98, 90 and 104from groups Ⅰ, Ⅱ, Ⅲ and Ⅳ,respectively) children were completed the intervention trial and the measurement of all biochemical indicators.After 6-months intervention, serum retinol status of children in group Ⅰ and group Ⅲ increased significantly (p<0.05).At the end of intervention,serum retinol levels of children in group Ⅰ and group Ⅲ was markedly higher than those of children in group Ⅱ and group Ⅳ (p<0.05).Hb levels of children in group Ⅰ, Ⅱ and Ⅲ got all significantly increased at the same degree after intervention.SF level of children in group Ⅰstatistically decreased after intervention (p<0.05), but increased in group Ⅱ (p<0.05).Only in group Ⅰ, the level of sTfR got markedly decreased after intervention (p<0.05).TRF-F index and BTIC showed the same change after intervention.In group Ⅱ and group Ⅲ, the levels of TRF-F index and BTIC had statistically increased with the same degree after intervention, but not for the levels of children in group Ⅰ and group Ⅳ (p>0.05).Conclusion: The impact of vitamin A intervention on iron metabolic homeostasis was mainly manifested in storage and mobilization,but no direct effect on total body iron content and iron absorption in intestine.