The window of lactation is a critical period during which nutritional and environmental exposures impact lifelong metabolic disease risk. Significant organ and tissue development, organ expansion and maturation of cellular functions occur during the lactation period, making this a vulnerable time during which transient insults can have lasting effects. This review will cover current literature on factors influencing lactational programming such as milk composition, maternal health status and environmental endocrine disruptors. The underlying mechanisms that have the potential to contribute to lactational programming of glucose homeostasis will also be addressed, as well as potential interventions to reduce offspring metabolic disease risk.

Overweight and obesity (OW/OB) impact half of the pregnancies in the United States and can have negative consequences for offspring health. Studies are limited on human milk alterations in the context of maternal obesity. Alterations in milk are hypothesized to impact offspring development during the critical period of lactation. We aimed to evaluate the relationships between mothers with OW/OB (body mass index [BMI] ≥25 kg/m2), infant growth, and selected milk nutrients. We recruited mother–infant dyads with pre‐pregnancy OW/OB and normal weight status. The primary study included 52 dyads with infant growth measures through 6 months. Thirty‐two dyads provided milk at 2 weeks, which was analysed for macronutrients, long‐chain fatty acids, and insulin. We used multivariable linear regression to examine the association of maternal weight status with infant growth, maternal weight status with milk components, and milk components with infant growth. Mothers with OW/OB had infants with higher weight‐for‐length (WFL) and BMI Z‐scores at birth. Mothers with OW/OB had higher milk insulin and dihomo‐gamma‐linolenic, adrenic, and palmitic acids and reduced conjugated linoleic and oleic acids. N6 long‐chain polyunsaturated fatty acid (LC‐PUFA)‐driven factor 1 was associated with higher WFL, lower length‐for‐age (LFA), and lower head circumference‐for‐age Z‐scores change from 2 weeks to 2 months in human milk‐fed infants, whereas N6 LC‐PUFA‐driven factor 5 was associated with lower LFA Z‐score change. Human milk composition is associated with maternal pre‐pregnancy weight status and composition may be a contributing factor to early infant growth trajectory.

In breastfed infants, human milk provides the primary source of iodine to meet demands during this vulnerable period of growth and development. Iodine is a key micronutrient that plays an essential role in hormone synthesis. Despite the importance of iodine, there is limited understanding of the maternal factors that influence milk iodine content and how milk iodine intake during infancy is related to postnatal growth. We examined breast milk samples from near 2 weeks and 2 months post-partum in a mother-infant dyad cohort of mothers with pre-pregnancy weight status defined by body mass index (BMI). Normal (NW, BMI < 25.0 kg/m2) is compared to overweight/obesity (OW/OB, BMI ≥ 25.0 kg/m2). The milk iodine concentration was determined by inductively coupled plasma mass spectrometry. We evaluated the associations between iodine content at 2 weeks and infant anthropometrics over the first year of life using multivariable linear mixed modeling. Iodine concentrations generally decreased from 2 weeks to 2 months. We observed no significant difference in iodine based on maternal weight. A higher iodine concentration at 2 weeks was associated with a larger increase in infant weight-for-age and weight-for-length Z-score change per month from 2 weeks to 1 year. This pilot study shows that early iodine intake may influence infant growth trajectory independent of maternal pre-pregnancy weight status.

Background The use of donor human milk is rising. Maternal awareness of donor human milk use, milk donation, and milk banks has not been well described in the United States. Research Aims To explore maternal experience, knowledge, and attitudes regarding donor human milk use and milk donation. We also assessed counseling by medical providers about donor human milk use and donation. Methods A cross-sectional prospective survey design was used in this study. We anonymously surveyed mothers ( N = 73) attending the 1 to 2-week well newborn appointment. Analyses were completed using one-way ANOVA and logistic regression. Results Participants’ infants primarily received their own mother’s milk (87%, n = 61). No infants received donor human milk, but 4% ( n = 3) of participants donated milk. The majority of participants had positive responses to attitudinal statements about donor milk. When presented with a hypothetical scenario, participants chose formula (89%, n = 59) over donor human milk (11%, n = 7) for their infant. Moreover, if donor human milk was the only option available, they chose donor human milk from a relative or friend (60%, n = 40) over a milk bank (40%, n = 26). Medical providers had discussed donor human milk use or donation with 4% ( n = 3) of participants. Conclusions The majority of participants previously had minimal experience using donor human milk and limited knowledge regarding donor human milk and milk banks. According to participants, medical providers did not routinely discuss milk donation and the role of donor human milk with families.

Summary Background Compared to the exhaustive study of transgenerational programming of obesity and diabetes through exposures in the prenatal period, postnatal programming mechanisms are understudied, including the potential role of breast milk composition linking maternal metabolic status (body mass index and diabetes) and offspring growth, metabolic health and future disease risk. Methods This narrative review will principally focus on four emergent bioactive compounds [microRNA's (miRNA), lipokines/signalling lipids, small molecules/metabolites and fructose] that, until recently were not known to exist in breast milk. The objective of this narrative review is to integrate evidence across multiple fields of study that demonstrate the importance of these compositional elements of breast milk during lactation and the subsequent effect of breast milk components on the health of the infant. Results Current knowledge on the presence of miRNA's, lipokines/signalling lipids, small molecules/metabolites and fructose in breast milk and their associations with infant outcomes is compelling, but far from resolved. Two themes emerge: (1) maternal metabolic phenotypes are associated with these bioactives and (2) though existing in milk at low concentrations, they are also associated with offspring growth and body composition. Conclusion Breast milk research is gaining momentum though we must remain focused on understanding how non‐nutritive bioactive components are affected by the maternal phenotype, how they subsequently impact infant outcomes. Though early, there is evidence to suggest fructose is associated with fat mass in the 1st months of life whereas 12,13 diHOME (brown fat activator) and betaine are negatively associated with early adiposity and growth.