Objective      A randomized trial of vitamin A/zinc supplementation in preschool children was conducted to analyze the impact of vitamin A (VA)/zinc on feedback regulatory effect of hemoglobin (Hb) on erythropoietin (EPO) level.       Methods      Two kindergartens were randomly selected out of 7 in a subu

rb of Chongqing

China. According to the method of stratified random cluster sampling in kindergartens

a total of 232 preschool children who met the eligibility criteria aged between 3-6 years were assigned randomly to 2 treatment groups: VA group (A group) and VA plus zinc group (AZ group). The groups were sub-grouped into subgroup Ⅰ (anemia and VA deficiency)

subgroup Ⅱ (normal Hb and VA deficiency)

and subgroup Ⅲ (anemia and normal VA). The supplementation lasted for 6 months. Hb

VA

EPO and Zn concentrations before and after the intervention were measured.       Results      After 6 months of supplementation

the VA concentration in AZ group was significantly increased by 0.05 μmol/L (

P

0.05)

whereas it was not significantly increased in A group. A group and AZ group showed significantly improved zinc concentration of 2.95 μmol/L and 3.67 μmol/L (

P

0.05

P

0.01)

respectively. Hb and EPO showed significant increases in the 2 groups (

P

0.05). Moreover

the prevalence of anemia was decreased significantly in A group and AZ group. The slope of the regression line between Log10 EPO and Hb in A group was significantly decreased by -0.009 9 (

P

0.05)

while it was not significantly changed in AZ group. There were significant increases of Hb concentration in subgroup Ⅰ and subgroup Ⅲ (

P

0.05)

and Hb was increased more significantly in subgroup Ⅲ than in subgroup Ⅱ. EPO was increased more significantly in subgroup Ⅰ than in the other 2 subgroups.       Conclusions      VA level can influence the feedback regulatory effect of Hb on EPO level.