Effects of various processes and lactation time on macronutrients in breast milk

Abstract

Objective To analyze Holder pasteurization, temperature and duration of frozen, duration of continuous breast milk pumping and types of pumping tube on macronutrients and total energy in breast milk and the circadian variation of macronutrients and energy content of breast milk. Methods Two hundred and two breast milk samples were collected from healthy mothers of 188 infants who were hospitalized in Department of Pediatrics, Obstetrics and Gynecology Hospital Affiliated to Nanjing Medical University from April 2016 to December 2016. Fat, protein, carbohydrate and energy contents of the breast milk samples were detected both before and after various processes to analyze the influence of Holder pasteurization, frozen storage conditions (temperature and time), duration of continuous pumping and types of pumping tube and to observe the variations within a single day. Paired t-test, repeated-measures analysis of variance, one-way analysis of variance and LSD-t test were used for statistical analysis. Results The contents of fat, protein and energy in breast milk were significantly decreased [(3.69±0.98) vs (4.22±1.00) g/dl, t=9.405; (2.12±0.34) vs (2.21±0.34) g/dl, t=4.785; (69.77±9.35) vs (74.94±9.53) kcal/dl (1 kcal=4.184 kJ), t=9.470], while the carbohydrate content was increased [(6.66±0.17) vs (6.62±0.17) g/dl, t=-3.442] after Holder pasteurization comparing with those before (all P<0.01). Breast milk frozen at -80 ℃ had higher protein content than that frozen at -20 ℃(Ftemperature=4.990, Ptemperature=0.027). Breast milk stored at -20 ℃ for 7, 15, 30, 60 and 90 days showed significantly decreased fat, protein and energy contents as compared with those in fresh breast milk, while the carbohydrate contents in the breast milk samples stored at -20 ℃ for 15, 30 and 60 days were significantly increased and that kept for 90 days were lower than those at 30 and 60 days (LSD-t test, P<0.05). Compared with fresh breast milk, breast milk stored at -80 ℃ showed significantly decreased fat, protein and energy contents at 60 d and 90 d, but increased carbohydrate content at 60 d (LSD-t test, P<0.05). Compared with fresh breast milk, breast milk which was pumped at 1, 2 or 3 h through gastric tube (size 6,8 or 10) or transfusion connecting pipe had lower fat content (LSD-t test, P<0.05). Compared with fresh milk, breast milk had lower energy content on condition that it was pumped through gastric tube size 6 at 2 or 3 h or through gastric tube size 8 or 10 or transfusion connecting pipe at 1, 2 or 3 h (LSD-t test, P<0.05). Breast milk secreted from 12:01 to 15:00 had higher fat and energy contents [(5.16±0.93) g/dl and (86.96±9.35) kcal/dl] than that secreted from 00:01 to 03:00[(4.54±0.75) g/dl and (80.77±7.75) kcal/dl], from 03:01 to 06:00 [(4.61±0.75) g/dl and (81.44±7.69) kcal/dl] or from 21:01 to 24:00 [(4.71±0.88) g/dl and (82.44±8.82) kcal/dl]. Moreover, breast milk secreted from 09:01 to 12:00 had higher fat and energy contents [(5.01±0.94) g/dl and (85.31±9.62) kcal/dl] than that secreted from 00:01 to 03:00, and that secreted from 09:01 to 12:00 had higher fat contents than that secreted from 03:01 to 06:00 (LSD-t test, P<0.05). Conclusions Fresh breast milk is better than processed milk to meet the infantile need for growth and development. Key words: Milk, human; Breast milk expression; Time; Fats; Proteins; Carbohydrates