Presented at the Neonatal Society 2015 Spring Meeting.
Andreas NJ1, Hyde MJ1, Jeffries S1, Holmes E2, Modi N1
1 Section of Neonatal Medicine, Department of Medicine, Imperial College London, UK
2 Section of Computational and Systems Medicine, Faculty of Medicine, Imperial College London, UK
Background: Previous research on donor breast milk has suggested a positive correlation between maternal Body Mass Index (BMI) and breast milk concentration of protein, carbohydrate and fat (1). We sought to further study the relationship between maternal BMI and fore and hind milk composition, over the first three months of lactation. We tested the hypothesis that we would observe differences in breast milk composition between high and normal BMI mothers.
Methods: We obtained fore and hind milk samples from 95 mothers delivering at full-term, at seven days and three months post-partum. 52 mothers had a BMI <25, 43 a BMI >25. Samples were frozen at -80°C until analysis, when they were thawed and homogenised using sonication prior to analysis. Macronutrient content was determined using mid-infrared spectroscopy (Miris Human Milk Analyser loaned by MIRIS AB, Sweden), in accordance with manufacturer instructions. We used ANOVA (SPSS) to assess the relationship of breast milk macronutrient content in relation to maternal BMI. The study received Research Ethics approval (12/LO/0203) and was funded by Westminster Medical School Research Trust.
Results: We obtained a total of 284 samples (1 week, fore milk=95, hind milk=40; 3 months, fore milk=90, hind milk=59). We found no statistically significant or clinically relevant correlations between maternal BMI and breast milk protein, carbohydrate or fat content at either of the time points, nor did maternal pregnancy weight gain influence the concentration of macronutrients. In agreement with previous reports at three months only 24% of women with a BMI >25 were still breast feeding compared to 75% of mothers with a BMI <25. Also in keeping with other reports, we found that hind milk has significantly more fat and less carbohydrate than fore milk, regardless of stage of lactation. However, protein concentration in fore and hind milk differed with stage of lactation: at 7 days, there was no difference between fore and hind milk; but at 3 months there was more protein in hind milk (p=0.009). Between 7 days and 3 months of lactation, in fore milk, the concentration of fat remained stable, carbohydrate increased and protein decreased; in hind milk there were significant increases in fat and carbohydrate, but a significant decrease in protein.
Conclusion: In contrast to previous research, we did not observe any association between maternal BMI and breast milk macronutrient content at any of the time points studied. Our data suggest that breast milk composition is regulated independent of maternal BMI.
Corresponding author: n.andreas11@imperial.ac.uk
References
1. Michaelsen, K. F. J Pediatr Gastroenterol Nutr. 1990 11(2); p. 229-39