Macronutrients, immunoglobulin A and total antioxidant capacity of human milk during prolonged lactation

Abstract

Background: A longer duration of breastfeeding of up to two years is encouraged by many health authorities, but there is limited information regarding the composition of the milk after one year postpartum. The aim of the study was to determine the longitudinal changes in human milk macronutrients, immunoglobulin A (IgA) and total antioxidant capacity (TAC) during prolonged lactation. Methods: One hundred eighty-four breastfeeding mothers with full-term healthy children who had been lactating from 1 to 24 months were recruited from January 2019 to April 2019. Human milk was biochemically analyzed for protein and carbohydrate content by colorimetric assays. The fat content was determined by capillary centrifugation, and the energy content was calculated from the results of centrifugation. IgA levels and TAC were determined by ELISA and a Trolox equivalent antioxidant capacity (TEAC) assay, respectively.Pearson correlation analysis was used to determine the association of milk composition with the month of lactation. Results: The concentrations of protein, fat, energy and IgA were positively correlated with the duration of lactation ( r = 0.15, p < 0.05; r = 0.23, p < 0.05; r = 0.23, p < 0.05 and r = 0.29, p < 0.05, respectively). No significant correlations of the carbohydrate concentrations or TAC with the duration of lactation was observed ( r = 0.10, p > 0.05 and r = -0.07, P > 0.05, respectively). Conclusions: We demonstrated that protein, fat, IgA and energy contents increasedduring prolonged lactation lasting up to twoyears postpartum, while carbohydrateconcentrationand TACwerenot related to lactation duration. Based on the results, lactating mothers should be encouraged to continue breastfeeding for at least two years postpartum.