RESUMO
OBJECTIVE: Some recent studies found that high prevalence of vitamin A deficiency in the breastfed children. This study aimed to understand the differences in serum retinol level between breastfed and bottle-fed children aged 0 to 23 months and the possible causes of low level of serum retinol for the breastfed children. METHODS: Data for children aged 0 to 23 months were extracted from a population-based cross sectional study for vitamin A nutrition status. Fluorescence method was used to measure the serum retinol. Mothers or caregivers were asked to answer a pre-designed questionnaire and socioeconomic status, peri-natal care, breastfeeding status, morbidity histories and other related factors were collected. Semi-quantitative food frequency questionnaire was used to investigate the child's dietary intake one week prior to the survey. Data were analyzed using SAS 8.1. RESULTS: Of 401 children aged 0 to 23 months, the breastfeeding rate was 50.37%. The means of the serum retinol level between bottle-fed (30.67 +/- 0.57) microg/dl and the breastfed children (27.60 +/- 0.56) microg/dl was significantly different (P < 0.01). The corresponding figures were (31.82 +/- 0.98) microg/dl and (29.46 +/- 0.96) microg/dl after adjustment for confounders, which also showed significant difference (P < 0.01). After stratified by age groups, the breastfeeding rates in the 0-, 6-, 12- and 18-months groups were 92.1%, 70.1%, 32.0% and 17.1%, respectively. We calculated the difference in means of the serum retinol level between the bottle-fed and breastfed children for each of four age groups, and the 95% confidence limits of the differences. The differences in means and the 95% confidence limits for 0-, 6-, 12- and 18-months group were 4.70 microg/dl (-2.52-1.92), 0.82 microg/dl (-2.32-3.95), 2.95 microg/dl (-0.68-6.58) and 6.05 microg/dl (2.34-9.77), respectively. After adjustment for confounders and covariates, the adjusted figures were 0.00 microg/dl (-7.18-7.19), 1.35 microg/dl (-1.76-4.45), 2.92 microg/dl (-0.82-6.65) and 4.26 microg/dl (0.71-7.81), respectively. The significant difference in means of serum retinol level was only found in the 18-months group before or after adjustments (P < 0.01 for both). The Cochrane-Atmitage chi square trend test showed that the breastfed children tended to have lower frequencies of complementary dietary intakes than that of the bottle-fed aged 12 months and above. CONCLUSIONS: The breastfed children aged 0 to 23 months had relative low serum retinol level while compared with the bottle-fed. However, the significant differences seemed to be only confined to those aged 18 months and above. Low level of vitamin A in breast milk and low frequent complimentary food supplements might have served as the potential for the differences.