Culturable micro-organisms in human milk were found to be associated with maternal weight, diet and age during early lactation

The association between maternal body mass index and breast milk composition: a systematic review

CONTEXT

Breast milk composition is influenced by many factors, ranging from maternal nutritional status to infant sex. Previous studies have explored the relationship between maternal body mass index (BMI) and breast milk composition; however, the findings have been inconsistent and controversial.

OBJECTIVE

To systematically review the evidence on the association of maternal weight and BMI with breast milk composition.

DATA SOURCES

The PubMed and Scopus databases were searched up to May 3, 2023, using the following search strategy: ("maternal weight" OR "maternal BMI" OR "mother's weight" OR "mother's BMI") AND ("maternal milk" OR "human milk" OR "breast milk").

DATA EXTRACTION

A total of 83 publications, involving data from more than 11 310 lactating women, were identified. All extracted data were compiled, compared, and critically analyzed.

DATA ANALYSIS

Overall, maternal BMI was associated with higher levels of leptin and insulin, and the ratio of omega-6 to omega-3 polyunsaturated fatty acids in breast milk. However, no conclusive associations were found between maternal BMI and the levels of energy, macronutrients, micronutrients, and other components of breast milk.

CONCLUSIONS

This systematic review provides robust evidence supporting a positive correlation between maternal BMI and breast milk concentrations of leptin, insulin, and the omega-6 to omega-3 polyunsaturated fatty acid ratio. Nevertheless, disparities in findings are noticeable for other constituents of breast milk. To comprehensively grasp the influence of maternal weight and BMI on breast milk composition, further research endeavors are imperative.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42023458667.

Effect of Thermostable Enzymes Produced by Psychrotrophic Bacteria in Raw Milk on the Quality of Ultra-High Temperature Sterilized Milk

Ultra-high temperature sterilized milk (UHT) is a popular dairy product known for its long shelf life and convenience. However, protein gel aging and fat quality defects like creaming and flavor deterioration may arise during storage. These problems are primarily caused by thermostable enzymes produced by psychrotrophic bacteria. In this study, four representative psychrotrophic bacteria strains which can produce thermostable enzymes were selected to contaminate UHT milk artificially. After 11, 11, 13, and 17 weeks of storage, the milk samples, which were contaminated with Pseudomonas fluorescens, Chryseobacterium carnipullorum, Lactococcus raffinolactis and Acinetobacter guillouiae, respectively, demonstrated notable whey separation. The investigation included analyzing the protein and fat content in the upper and bottom layers of the milk, as well as examining the particle size, Zeta potential, and pH in four sample groups, indicating that the stability of UHT milk decreases over time. Moreover, the spoiled milk samples exhibited a bitter taste, with the dominant odor being attributed to ketones and acids. The metabolomics analysis revealed that three key metabolic pathways, namely ABC transporters, butanoate metabolism, and alanine, aspartate, and glutamate metabolism, were found to be involved in the production of thermostable enzymes by psychrotrophic bacteria. These enzymes greatly impact the taste and nutrient content of UHT milk. This finding provides a theoretical basis for further investigation into the mechanism of spoilage.

Maternal weight status and the composition of the human milk microbiome: A scoping review

The human milk microbiome is thought to partly contribute to the assembly of the infant gut microbiome, a microbial community with important implications for infant health and development. While obesity has well-established links with the adult gut microbiome, less is known about how it affects the human milk microbiome. In this scoping review, we synthesize the current literature on the microbial composition of human milk by maternal weight status, defined broadly as BMI (prepregnancy and postpartum) and gestational weight gain (GWG). This study followed the a priori protocol published in Prospero (registration #: CRD42020165633). We searched the following databases for studies reporting maternal weight status and a characterization of milk microbiota through culture-dependent and culture-independent methods: MEDLINE, Embase, Web of Science, CINAHL, and Scopus. After screening 6,365 studies, we found 20 longitudinal and cross-sectional studies investigating associations between maternal weight status and the composition of the milk microbiome. While some studies reported no associations, many others reported that women with a pre-pregnancy or postpartum BMI characterized as overweight or obese, or with excessive GWG, had higher abundances of the genus Staphylococcus, lower Bifidobacterium abundance, and lower alpha diversity (within-sample diversity). This review suggests that maternal weight status is minorly associated with the composition of the milk microbiome in various ways. We offer potential explanations for these findings, as well as suggestions for future research.