Human Milk Oligosaccharide Compositions Illustrate Global Variations in Early Nutrition

Exploring the impact of maternal factors and dietary habits on human milk oligosaccharide composition in early breastfeeding among Mexican women

Human milk oligosaccharides (HMOs) promote adequate intestinal microbiota development and favor the immune system's maturation and cognitive development. In addition to non-modifiable factors, HMOs composition can be influenced by other factors like body mass index and eating habits, but the reports are discrepant. The aim of this work was to describe the correlation between maternal factors and HMOs concentration in colostrum in 70 women from northeastern Mexico categorized into women with normal weight and women with overweight or obesity. The absolute concentration of six HMOs were significantly lower in women with overweight or obesity compared to women with normal weight (LNFPI p = 0.0021, 2'-FL p = 0.0304, LNT p = 0.0492, LNnT p = 0.00026, 3'-SL p = 0.0476, 6'-SL p = 0.00041). Another main finding was that the frequency of consumption of food groups such as vegetables, fruits and meats was positively correlated to specific HMOs (Poblano chili and 2'-FL; rs = 0.702, p = 0.0012; Orange or tangerine and 3-FL; rs = 0.428, p = 0.0022; Chicken and 2'-FL; rs = 0.615, p = 0.0039). This study contributes to the elucidation of how maternal factors influence the composition of HMOs and opens possibilities for future research aimed at mitigating overweight or obesity, consequently improving the quality of human milk.

The Role of Maternal Secretor Status and Human Milk Oligosaccharides on Early Childhood Development: A Systematic Review and Meta-Analysis

Background: Breast milk is the gold standard of infant nutrition, delivering nutrients and bioactive molecules as needed to support optimal infant growth and cognitive development. Increasing evidence links human milk oligosaccharides (HMOs) to these early childhood development milestones. Aims: To summarize and synthesize the evidence relating to HMOs and infant brain development, physical growth, and cognitive development. In addition, HMO concentrations in secretor and nonsecretor mothers were compared via a meta-analysis. Study Design: A systematic review and meta-analysis were carried out in accordance with the PRISMA statement. This review used three databases (PubMed, Scopus, and Web of Science) and was limited to English-language articles published between 2000 and June 30, 2023. Results: The initial searches yielded 245 articles, 27 of which were included in the systematic review and 12 in the meta-analysis. The meta-analysis revealed a substantial between-study heterogeneity, I2 = 97.3%. The pooled effect was 0.21 (95% CI: -0.41 to 0.83; p = 0.484), indicating that secretors had higher HMO concentrations, although this difference was not statistically significant. At one month of age, 2'FL, 3FL, and 3'SL play an important role in brain maturation and thus play a critical role in cognitive development. Secretors produce higher concentrations of 2'FL and 3'SL, explaining the benefits to infants of secretor mothers. Growth velocity was correlated to fucosylated and sialylated HMO concentrations, with lower concentrations linked to stunting. Conclusions: According to evidence from the systematically reviewed articles, HMOs are essential for a child's early development, but the extent to which they have an impact depends on maternal secretor status.

Evaluation of Prebiotic Glycan Composition in Human Milk and Infant Formula: Profile of Galacto-Oligosaccharides and Absolute Quantification of Major Milk Oligosaccharides by UPLC-Cyclic IM-MS and UPLC-MS/MS

Prebiotic oligosaccharides have attracted immense interest in the infant formula (IF) industry due to their unique health benefits for infants. There is a need for the reasonable supplementation of prebiotics in premium IF products. Herein, we characterized the profile of galacto-oligosaccharides (GOS) in human milk (HM) and IF using ultrahigh-performance liquid chromatography-cyclic ion mobility-mass spectrometry (UPLC-cIM-MS) technique. Additionally, we further performed a targeted quantitative analysis of five essential HM oligosaccharides (HMOs) in HM (n = 196), IF (n = 50), and raw milk of IF (n = 10) by the high-sensitivity UPLC-MS/MS method. HM exhibited a more abundant and variable HMO composition (1183.19 to 2892.91 mg/L) than IF (32.91 to 56.31 mg/L), whereas IF contained extra GOS species and non-negligible endogenous 3'-sialyllactose. This also facilitated the discovery of secretor features within the Chinese population. Our study illustrated the real disparity in the prebiotic glycome between HM and IF and provided crucial reference for formula improvement.

Potential biological functions and future perspectives of sialylated milk oligosaccharides

Sialyllactoses (SLs) primarily include sialylated human milk oligosaccharides (HMOs) and bovine milk oligosaccharides (BMOs). First, the safety assessment of 3'-sialyllactose (3'-SL) and 6'-sialyllactose (6'-SL) revealed low toxicity in various animal models and human participants. SLs constitute a unique milk component, highlighting the essential nutrients and bioactive components crucial for infant development, along with numerous associated health benefits for various diseases. This review explores the safety, biosynthesis, and potential biological effects of SLs, with a specific focus on their influence across various physiological systems, including the gastrointestinal system, immune disorders, rare genetic disorders (such as GNE myopathy), cancers, neurological disorders, cardiovascular diseases, diverse cancers, and viral infections, thus indicating their therapeutic potential.

Linking human milk oligosaccharide metabolism and early life gut microbiota: bifidobacteria and beyond

SUMMARYHuman milk oligosaccharides (HMOs) are complex, multi-functional glycans present in human breast milk. They represent an intricate mix of heterogeneous structures which reach the infant intestine in an intact form as they resist gastrointestinal digestion. Therefore, they confer a multitude of benefits, directly and/or indirectly, to the developing neonate. Certain bifidobacterial species, being among the earliest gut colonizers of breast-fed infants, have an adapted functional capacity to metabolize various HMO structures. This ability is typically observed in infant-associated bifidobacteria, as opposed to bifidobacteria associated with a mature microbiota. In recent years, information has been gleaned regarding how these infant-associated bifidobacteria as well as certain other taxa are able to assimilate HMOs, including the mechanistic strategies enabling their acquisition and consumption. Additionally, complex metabolic interactions occur between microbes facilitated by HMOs, including the utilization of breakdown products released from HMO degradation. Interest in HMO-mediated changes in microbial composition and function has been the focal point of numerous studies, in recent times fueled by the availability of individual biosynthetic HMOs, some of which are now commonly included in infant formula. In this review, we outline the main HMO assimilatory and catabolic strategies employed by infant-associated bifidobacteria, discuss other taxa that exhibit breast milk glycan degradation capacity, and cover HMO-supported cross-feeding interactions and related metabolites that have been described thus far.

Online LC-ESI-MS/MS comparative analysis of N/O-glycopatterns in human colostrum from different ethnic groups in Northwest China

Human milk oligosaccharides, including free oligosaccharides and glycoconjugates, exert a key role in neonatal health and development. Changes in free oligosaccharides of milk from different ethnic groups have been documented. In this study, human milk was collected from Han, Hui, and Tibetan populations in northwest China, and differences in N/O-glycome among these three ethnic groups were systematically compared using online high-performance liquid chromatography-tandem mass spectrometry. Among the 63 detected N-glycans, 35 showed significant differences between the three ethnic groups (p < 0.05). Among the 70 detected O-glycans, four neutral O-glycans and six acidic O-glycans exhibited significant differences among the three ethnic groups (p < 0.05), with six acidic O-glycans reported for the first time. Overall, the extent of milk N/O-glycosylation was higher in the Han population than in the Hui or Tibetan groups. This trend was particularly pronounced for the main sialylated N/O-glycans. Except for sulfated O-glycans, which were higher in the milk from Tibetan mothers, the other types of N/O-glycans were present in similar proportions across all ethnic groups. Understanding the composition of N/O-glycans in human milk can help research on the structure-function relationship of glycans.

Mechanism of 2'-fucosyllactose degradation by human-associated Akkermansia

Among the first microorganisms to colonize the human gut of breastfed infants are bacteria capable of fermenting human milk oligosaccharides (HMOs). One of the most abundant HMOs, 2'-fucosyllactose (2'-FL), may specifically drive bacterial colonization of the intestine. Recently, differential growth has been observed across multiple species of Akkermansia on various HMOs including 2'-FL. In culture, we found growth of two species, A. muciniphila MucT and A. biwaensis CSUN-19,on HMOs corresponded to a decrease in the levels of 2'-FL and an increase in lactose, indicating that the first step in 2'-FL catabolism is the cleavage of fucose. Using phylogenetic analysis and transcriptional profiling, we found that the number and expression of fucosidase genes from two glycoside hydrolase (GH) families, GH29 and GH95, vary between these two species. During the mid-log phase of growth, the expression of several GH29 genes was increased by 2'-FL in both species, whereas the GH95 genes were induced only in A. muciniphila. We further show that one putative fucosidase and a β-galactosidase from A. biwaensis are involved in the breakdown of 2'-FL. Our findings indicate that the plasticity of GHs of human-associated Akkermansia sp. enables access to additional growth substrates present in HMOs, including 2'-FL. Our work highlights the potential for Akkermansia to influence the development of the gut microbiota early in life and expands the known metabolic capabilities of this important human symbiont.IMPORTANCEAkkermansia are mucin-degrading specialists widely distributed in the human population. Akkermansia biwaensis has recently been observed to have enhanced growth relative to other human-associated Akkermansia on multiple human milk oligosaccharides (HMOs). However, the mechanisms for enhanced growth are not understood. Here, we characterized the phylogenetic diversity and function of select genes involved in the growth of A. biwaensis on 2'-fucosyllactose (2'-FL), a dominant HMO. Specifically, we demonstrate that two genes in a genomic locus, a putative β-galactosidase and α-fucosidase, are likely responsible for the enhanced growth on 2'-FL. The functional characterization of A. biwaensis growth on 2'-FL delineates the significance of a single genomic locus that may facilitate enhanced colonization and functional activity of select Akkermansia early in life.

Mechanism of 2'-Fucosyllactose degradation by Human-Associated Akkermansia

Among the first microorganisms to colonize the human gut of breastfed infants are bacteria capable of fermenting human milk oligosaccharides (HMOs). One of the most abundant HMOs, 2'-fucosyllactose (2'-FL), may specifically drive bacterial colonization of the intestine. Recently, differential growth has been observed across multiple species of Akkermansia on various HMOs including 2'FL. In culture, we found growth of two species, A. muciniphila Muc T and A. biwaensis CSUN-19, in HMOS corresponded to a decrease in the levels of 2'-FL and an increase in lactose, indicating that the first step in 2'-FL catabolism is the cleavage of fucose. Using phylogenetic analysis and transcriptional profiling, we found that the number and expression of fucosidase genes from two glycoside hydrolase (GH) families, GH29 and GH95, varies between these two species. During mid-log phase growth, the expression of several GH29 genes was increased by 2'-FL in both species, whereas the GH95 genes were induced only in A. muciniphila . We further show that one putative fucosidase and a β-galactosidase from A. biwaensis are involved in the breakdown of 2'-FL. Our findings indicate that that plasticity of GHs of human associated Akkermansia sp. enable access to additional growth substrates present in HMOs, including 2'-FL. Our work highlights the potential for Akkermansia to influence the development of the gut microbiota early in life and expands the known metabolic capabilities of this important human symbiont.

IMPORTANCE

Akkermansia are mucin degrading specialists widely distributed in the human population. Akkermansia biwaensis has recently been observed to have enhanced growth relative to other human associated Akkermansia on multiple human milk oligosaccharides (HMOs). However, the mechanisms for enhanced growth are not understood. Here, we characterized the phylogenetic diversity and function of select genes involved in growth of A. biwaensis on 2'-fucosyllactose (2'-FL), a dominant HMO. Specifically, we demonstrate that two genes in a genomic locus, a putative β-galactosidase and α-fucosidase, are likely responsible for the enhanced growth on 2'-FL. The functional characterization of A. biwaensis growth on 2'-FL delineates the significance of a single genomic locus that may facilitate enhanced colonization and functional activity of select Akkermansia early in life.

Lactational and geographical variation in the concentration of six oligosaccharides in Chinese breast milk: a multicenter study over 13 months postpartum

Introduction

Understanding the variations of oligosaccharide in breast milk contribute to better study how human milk oligosaccharides (HMOs) play a role in health-promoting benefits in infants.

Methods

Six abundant HMOs, 2'-fucosyllactose (2'-FL), 3-fucosyllactose (3-FL), Lacto-N-tetraose (LNT), Lacto-N-neotetraose (LNnT), 3'-sialyllactose (3'-SL) and 6'-sialyllactose (6'-SL), in breast milk collected at 0-5 days, 10-15 days, 40-45 days, 200-240 days, and 300-400 days postpartum from six locations across China were analyzed using high-performance anion-exchange chromatography-pulsed amperometric detector.

Results

The concentration of individual HMO fluctuated dynamically during lactational stages. The median ranges of 2'-FL, 3-FL, LNT, LNnT, 3'-SL, and 6'-SL across the five lactational stages were 935-2865 mg/L, 206-1325 mg/L, 300-1473 mg/L, 32-317 mg/L, 106-228 mg/L, and 20-616 mg/L, respectively. The prominent variation was observed in the content of 6'-SL, which demonstrates a pattern of initial increase followed by a subsequent decrease. Among the five lactational stages, the transitional milk has the highest concentration, which was 31 times greater than the concentration in mature milk at 300-400 days postpartum, where the content is the lowest. Geographical location also influenced the content of HMOs. LNT and LNnT were the highest in mature milk of mothers from Lanzhou among the six sites at 40-240 days postpartum. Breast milks were categorized into two groups base on the abundance of 2'-FL (high and low). There was no significant difference in the proportions of high and low 2'-FL phenotypes among the six sites, and the percentages of high and low 2'-FL phenotypes were 79% and 21%, respectively, across all sites in China.

Discussion

This study provided a comprehensive dataset on 6 HMOs concentrations in Chinese breast milk during the extended postpartum period across a wide geographic range and stratified by high and low 2'-FL phenotypes.

Creation of a milk oligosaccharide database, MilkOligoDB, reveals common structural motifs and extensive diversity across mammals

The carbohydrate fraction of most mammalian milks contains a variety of oligosaccharides that encompass a range of structures and monosaccharide compositions. Human milk oligosaccharides have received considerable attention due to their biological roles in neonatal gut microbiota, immunomodulation, and brain development. However, a major challenge in understanding the biology of milk oligosaccharides across other mammals is that reports span more than 5 decades of publications with varying data reporting methods. In the present study, publications on milk oligosaccharide profiles were identified and harmonized into a standardized format to create a comprehensive, machine-readable database of milk oligosaccharides across mammalian species. The resulting database, MilkOligoDB, includes 3193 entries for 783 unique oligosaccharide structures from the milk of 77 different species harvested from 113 publications. Cross-species and cross-publication comparisons of milk oligosaccharide profiles reveal common structural motifs within mammalian orders. Of the species studied, only chimpanzees, bonobos, and Asian elephants share the specific combination of fucosylation, sialylation, and core structures that are characteristic of human milk oligosaccharides. However, agriculturally important species do produce diverse oligosaccharides that may be valuable for human supplementation. Overall, MilkOligoDB facilitates cross-species and cross-publication comparisons of milk oligosaccharide profiles and the generation of new data-driven hypotheses for future research.

Determinants of human milk oligosaccharides profiles of participants in the STRONG kids 2 cohort

Introduction

Human milk oligosaccharides (HMOS) are indigestible carbohydrates that support infant development by establishing a healthy microbiota, preventing infectious diseases, and promoting immune and cognitive development. Individual HMOS have distinct functions based on their chemical structures. HMO profiles can vary largely among mothers, but the research on factors other than genetic background affecting HMO composition are limited.

Methods

In the present analysis, we examined the relationships between maternal characteristics and the HMO profiles of breastfeeding mothers (n = 392) in the STRONG kids 2 with the following demographic characteristics: average age: 30.8 y, 74.5% White, and 75.5% exclusively breastfeeding. Human milk samples were collected at 6 weeks postpartum and maternal information was obtained from self-reported surveys. Information on dietary intake changes since the participants have been breastfeeding was collected. HMO profiles were analyzed by high performance liquid chromatography coupled with mass spectrometry and secretor status was determined by the presence of four secretor markers [2′-fucosyllactose (2′-FL), LNFP I, LDFT, and TFLNH]. Spearmen correlation test was utilized to determine the relationships between individual HMOS and associations with maternal factors. Between-group differences in HMO relative abundances were examined with Kruskal-Wallis test.

Results

Among all participants, 71.9% were secretors and 28.1% were non-secretors. The relative abundances of all HMOS differed (p &lt; 0.05) by secretor status, with the exception for 6′-SL and 3′-SL. Positive correlations were observed among HMOS with similar structures, such as the 1,2-fucosylated HMOS. The abundances of selected HMOS were associated with maternal body weight, pregnancy complications, and dietary characteristics. Based on pre-pregnancy BMI, in all mothers, relative abundance of 3′-SL was significantly higher in overweight mothers than obese mothers (p = 0.013). In milk produced by non-secretor mothers, LNPF I + III abundances were greater in overweight than normal weight mothers (p = 0.020). Several HMO abundances were found to be associated with Gestational diabetes mellitus (GDM). Variations of HMO abundances were also observed with dietary food intake. In all mothers, egg consumption was positively correlated with LNT + LNnT (R = 0.13; p = 0.012) and cheese intake was positively associated with 2′-FL (R = 0.10; p = 0.046) and S-LNnH II (R = 0.11; p = 0.026) abundances.

Discussion

HMO profiles were found to be associated with maternal characteristics and intake. Future research will investigate associations between HMOS and maternal and infant outcomes.

Microbiota and growth among infants and children in low-income and middle-income settings

PURPOSE OF REVIEW

Adequate nutrition is essential but insufficient for optimal childhood growth and development. Increasingly, it is clear that the gut microbiota modulates childhood growth and may be particularly important in low-income and middle-income countries (LMIC), where growth faltering, undernutrition, environmental contamination and enteric pathogens are more common. We summarize recent evidence demonstrating the role of the gut microbiota in impacting childhood growth and interventions targeting the gut microbiota to impact growth in children in LMIC settings.

RECENT FINDINGS

Recent studies show that maturation of the infant microbiota is linked with the development of the immune system, which is key to host-microbe symbiosis. Infants lacking Bifidobacterium longum subsp. Infantis, which predominates breastfed microbiome, display immune activation while supplementation is linked to increased immune tolerance and among undernourished children, promotes growth. Microbiome-directed complimentary foods (MDCF) containing local ingredients is a novel strategy to promote gut microbiota development, especially among undernourished children and improve growth. Dietary patterns during pregnancy may drive selection of gut microbial species that impact infant health and growth.

SUMMARY

Growth patterns among children in LMIC settings are closely associated with the diversity and maturity of the infant microbiome. Prebiotics, probiotics, and synbiotics targeting microbiota dysbiosis may impact birth outcomes, infant immune development and infections, and childhood growth in LMIC settings.

Gut Microbiome Composition and Metabolic Capacity Differ by FUT2 Secretor Status in Exclusively Breastfed Infants

A major polymorphism in the fucosyltransferase2 (FUT2) gene influences risk of multiple gut diseases, but its impact on the microbiome of breastfed infants was unknown. In individuals with an active FUT2 enzyme (“secretors”), the intestinal mucosa is abundantly fucosylated, providing mutualist bacteria with a rich endogenous source of fucose. Non-secretors comprise approximately one-fifth of the population, and they lack the ability to create this enzyme. Similarly, maternal secretor status influences the abundance of a breastfeeding mother’s fucosylated milk oligosaccharides. We compared the impact of maternal secretor status, measured by FUT2 genotype, and infant secretor status, measured by FUT2 genotype and phenotype, on early infant fecal microbiome samples collected from 2-month-old exclusively breastfed infants (n = 59). Infant secretor status (19% non-secretor, 25% low-secretor, and 56% full-secretor) was more strongly associated with the infant microbiome than it was with the maternal FUT2 genotype. Alpha diversity was greater in the full-secretors than in the low- or non-secretor infants (p = 0.049). Three distinct microbial enterotypes corresponded to infant secretor phenotype (p = 0.022) and to the dominance of Bifidobacterium breve, B. longum, or neither (p < 0.001). Infant secretor status was also associated with microbial metabolic capacity, specifically, bioenergetics pathways. We concluded that in exclusively breastfed infants, infant—but not maternal—secretor status is associated with infant microbial colonization and metabolic capacity.

Gut microbiome function and composition in infants from rural Kenya and association with human milk oligosaccharides

The gut microbiota evolves rapidly after birth, responding dynamically to environmental factors and playing a key role in short- and long-term health. Lifestyle and rurality have been shown to contribute to differences in the gut microbiome, including Bifidobacterium levels, between infants. We studied the composition, function and variability of the gut microbiomes of 6- to 11-month-old Kenyan infants (n = 105). Shotgun metagenomics showed Bifidobacterium longum to be the dominant species. A pangenomic analysis of B. longum in gut metagenomes revealed a high prevalence of B. longum subsp. infantis (B. infantis) in Kenyan infants (80%), and possible co-existence of this subspecies with B. longum subsp. longum. Stratification of the gut microbiome into community (GMC) types revealed differences in composition and functional features. GMC types with a higher prevalence of B. infantis and abundance of B. breve also had a lower pH and a lower abundance of genes encoding pathogenic features. An analysis of human milk oligosaccharides (HMOs) classified the human milk (HM) samples into four groups defined on the basis of secretor and Lewis polymorphisms revealed a higher prevalence of HM group III (Se+, Le-) (22%) than in most previously studied populations, with an enrichment in 2'-fucosyllactose. Our results show that the gut microbiome of partially breastfed Kenyan infants over the age of six months is enriched in bacteria from the Bifidobacterium community, including B. infantis, and that the high prevalence of a specific HM group may indicate a specific HMO-gut microbiome association. This study sheds light on gut microbiome variation in an understudied population with limited exposure to modern microbiome-altering factors.

Translating neonatal microbiome science into commercial innovation: metabolism of human milk oligosaccharides as a basis for probiotic efficacy in breast-fed infants

For over a century, physicians have witnessed a common enrichment of bifidobacteria in the feces of breast-fed infants that was readily associated with infant health status. Recent advances in bacterial genomics, metagenomics, and glycomics have helped explain the nature of this unique enrichment and enabled the tailored use of probiotic supplementation to restore missing bifidobacterial functions in at-risk infants. This review documents a 20-year span of discoveries that set the stage for the current use of human milk oligosaccharide-consuming bifidobacteria to beneficially colonize, modulate, and protect the intestines of at-risk, human milk-fed, neonates. This review also presents a model for probiotic applications wherein bifidobacterial functions, in the form of colonization and HMO-related catabolic activity in situ, represent measurable metabolic outcomes by which probiotic efficacy can be scored toward improving infant health.

Human milk nutritional composition across lactational stages in Central Africa

The African region encompasses the highest undernutrition burden with the highest neonatal and infant mortality rates globally. Under these circumstances, breastfeeding is one of the most effective ways to ensure child health and development. However, evidence on human milk (HM) composition from African women is scarce. This is of special concern, as we have no reference data from HM composition in the context of food insecurity in Africa. Furthermore, data on the evolution of HM across lactational stages in this setting lack as well. In the MITICA study, we conducted a cohort study among 48 Central-African women and their 50 infants to analyze the emergence of gut dysbiosis in infants and describe the mother-infant transmission of microbiota between birth and 6 months of age. In this context, we assessed nutritional components in HM of 48 lactating women in Central Africa through five sampling times from week 1 after birth until week 25. Unexpectedly, HM-type III (Secretor + and Lewis genes -) was predominant in HM from Central African women, and some nutrients differed significantly among HM-types. While lactose concentration increased across lactation periods, fatty acid concentration did not vary significantly. The overall median level of 16 detected individual human milk oligosaccharides (HMOs; core structures as well as fucosylated and sialylated ones) decreased from 7.3 g/l at week 1 to 3.5 g/l at week 25. The median levels of total amino acids in HM dropped from 12.8 mg/ml at week 1 to 7.4 mg/ml at week 25. In contrast, specific free amino acids increased between months 1 and 3 of lactation, e.g., free glutamic acid, glutamine, aspartic acid, and serine. In conclusion, HM-type distribution and certain nutrients differed from Western mother HM.

Sodium and Potassium Concentrations and Somatic Cell Count of Human Milk Produced in the First Six Weeks Postpartum and Their Suitability as Biomarkers of Clinical and Subclinical Mastitis

The sodium (Na) concentration and the ratio of Na to potassium (K; Na/K) in human milk are used commonly as biomarkers of subclinical mastitis, but limited data exist on their relationship to and ability to predict clinical mastitis. Here, we assessed concentrations of Na, K, Na/K, and somatic cell count (SCC), a mammary health biomarker used in the dairy industry, in milk prospectively collected from both breasts of 41 women over the first 6 weeks postpartum. Although values differed over time postpartum, there were no differences in mean values between breasts. Nearly one-quarter (24%) of participants experienced clinical mastitis. Somatic cell counts >4.76 × 105 cells/mL were most strongly related to development of clinical mastitis in the following week (odds ratio, 7.81; 95% CI, 2.15−28.30; p = 0.002), although relationships were also observed for SCC > 4.00 × 105 cells/mL and Na concentration >12 mmol/L. Estimates of the prevalence of subclinical mastitis in women who never progressed to clinical mastitis differed by biomarker but ranged from 20 to 75%. Despite these findings, positive predictive values (PPV) of the biomarkers for identifying clinical mastitis were low (≤0.34), indicating additional research is needed to identify single biomarkers or composite measures that are highly specific, sensitive, and predictive of clinical mastitis in women.

Milk: A Scientific Model for Diet and Health Research in the 21st Century

The origin of lactation and the composition, structures and functions of milk's biopolymers highlight the Darwinian pressure on lactation as a complete, nourishing and protective diet. Lactation, under the driving pressure to be a sustainable bioreactor, was under selection pressure of its biopolymers with diverse functions acting from the mammary gland through the digestive system of the infant. For example, milk is extensively glycosylated and the glycan structures and their functions are now emerging. Milk contains free oligosaccharides; complex polymers of sugars whose stereospecific linkages are not matched by glycosidic enzymes within the mammalian infant gut. These glycan polymers reach the lower intestine undigested. In this microbe-rich environment, bacteria compete to release and ferment the sugars via different hydrolytic strategies. One specific type of bacteria, Bifidobacterium longum subsp. infantis, (B. infantis) is uniquely equipped with a repertoire of genes encoding enzymes capable of taking up, hydrolyzing and metabolizing the complex glycans of human milk. This combination of a distinct food supply and unique genetic capability shapes the composition and metabolic products of the entire microbial community within the lower intestine of breast fed infants. The intestinal microbiome dominated by B. infantis, shields the infant from the growth of gram negative enteropathogens and their endotoxins as a clear health benefit. The world is facing unprecedented challenges to produce a food supply that is both nourishing, safe and sustainable. Scientists need to guide the future of agriculture and food in response to these 21st century challenges. Lactation provides an inspiring model of what that future research strategy could be.