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Influence of Breastfeeding and Complementary Feeding on Serum and Erythrocyte Zinc Levels in Preterm and Term Infants: A Cross-sectional Study


 Background: Zinc is an important micronutrient involved in cell division, growth, and immune system function. Most studies evaluating the nutritional status related to zinc and prematurity were conducted with hospitalized preterm infants. These studies show controversial results regarding the prevalence of deficiency, clinical implications, and the effect of zinc supplementation on mortality, infectious diseases, and growth in these groups. This study aimed to compare serum and erythrocyte zinc levels in a group of preterm and term infants during complementary feeding and related the zinc levels to dietary intake, and current nutritional condition in both groups. Methods: Cross-sectional study with 43 preterm infants (24 to 33 weeks) aged 9-24 months (mean: 14.3±6.4 months), compared with 47 term healthy infants. Data collected: socioeconomic status and maternal health during pregnancy, dietary history, anthropometry (weight, height, and head circumference), and current dietary intake. Laboratory tests: blood count, serum and erythrocyte zinc concentrations, and C-reactive protein.Results: Males predominated (24, or 55.8%) in the preterm group; the mean birth weight was 1,245±381.7 grams. Serum zinc levels <65 µg/dL and anemia were observed in four preterm (5.1%) and four term infants (5.3%), respectively. No infant had erythrocyte zinc < 40 µg/gHb. The variables independently associated with serum zinc levels were breastfeeding at the time of evaluation (20.11 µg/dL; 95% CI 9.62 to 30.60; p<0.001) and late (4-7 months) introduction of complementary feeding (6.6 µg/dL; 95% CI 5.3 to 11.4; p<0.001). Breastfeeding was also independently and directly associated with erythrocyte zinc levels (18.8 ug/dL; 95% CI 3.7 to 33.8; p=0.015). Conclusions: No difference was observed in the nutritional status related to zinc between preterm and term infants during complementary feeding. Serum and erythrocyte zinc levels were influenced by breastfeeding and the onset of solid foods.