Background The maternal buffering hypothesis posits that human lactation biology can buffer milk against the mild-to-moderate malnutrition that occurred routinely in evolutionary history through the mobilization of maternal body reserves. This perspective may provide insights for understanding human milk immune content variation, such as milk sIgA, which protects infants’ intestines from microbial colonization and prevents diarrheal disease. Objective To investigate how maternal delivery of sIgA to milk may vary in a way that can buffer milk against maternal malnutrition, while taking into consideration infants’ varying needs for immune protection across age or by sex. Methodology A cross-sectional study analyzed archived milk specimens from breastfeeding mothers in Ariaal communities of northern Kenya surveyed during the 2006 Horn-of-Africa drought. Multiple regression models for ln-transformed sIgA were constructed using maternal nutrition, infant age/sex and their interactions as predictors. Maternal nutrition variables included iron-deficiency anemia (IDA), vitamin A deficiency (VAD) and mid-upper arm circumference (MUAC). Infant vulnerability was considered high in young age and/or male sex. Results and implications Milk sIgA did not significantly differ by maternal IDA. Milk sIgA increased with infant age and maternal MUAC (n = 202). Significant interactions were observed between infant age and maternal VAD and between infant sex and maternal MUAC, such that milk sIgA content was low for younger infants particularly among VAD mothers, while among mothers with low MUAC, sIgA was lower for male infants. Results imply that mothers’ ability to deliver/buffer milk sIgA may be lowered when nutritional stress is combined with high infant vulnerability to infection. Lay Summary Human milk sIgA antibody content was low for younger infants among vitamin A deficient mothers. Among mothers with small arm-circumference, milk sIgA was lower for sons. Double burden of raising young or male infants with high needs for immune protection and being malnourished, might lower maternal sIgA delivery to milk.

Background: Maternal anemia has adverse consequences for the mother-infant dyad. To evaluate whether and how milk nutrient content may change in ways that could "buffer" infants against the conditions underlying maternal anemia, this study assessed associations between milk macronutrients and maternal iron-deficiency anemia (IDA), non-iron-deficiency anemia (NIDA), and inflammation.Methods: A secondary analysis of cross-sectional data and milk from northern Kenya was conducted (n = 204). The combination of hemoglobin and transferrin receptor defined IDA/NIDA. Elevated serum C-reactive protein defined acute inflammation. The effects of IDA, NIDA, and inflammation on milk macronutrients were evaluated in regression models.Results: IDA (β = 0.077, p = .022) and NIDA (β = 0.083, p = .100) predicted higher total protein (ln). IDA (β = −0.293, p = .002), NIDA (β = −0.313, p = .047), and inflammation (β = −0.269, p = .007) each predicted lower fat (ln); however, anemia accompanying inflammation predicted higher fat (β = 0.655, p = .007 for IDA and β = 0.468, p = .092 for NIDA). NIDA predicted higher lactose (β = 1.020, p = .003).Conclusions: Milk macronutrient content both increases and decreases in the presence of maternal anemia and inflammation, suggesting a more complicated and dynamic change than simple impairment of nutrient delivery during maternal stress. Maternal fat delivery to milk may be impaired under anemia. Mothers may buffer infant nutrition against adverse conditions or poor maternal health by elevating milk protein (mothers with IDA/NIDA), lactose (mothers with NIDA), or fat (mothers with anemia and inflammation). This study demonstrates the foundational importance of maternal micronutrient health and inflammation or infection for advancing the ecological understanding of human milk nutrient variation.

Objectives This study explored differing levels of macronutrients in breast milk in relation to maternal anemia and hemoglobin. Methods Archived milk specimens and data from a cross‐sectional sample of 208 breastfeeding mothers in northern Kenya, originally collected in 2006, were analyzed; data included milk fat, maternal hemoglobin concentration, and anemia status (anemia defined as hemoglobin <12 g/dL). Total protein and lactose were measured and energy was calculated. To explore the association between milk outcomes (fat, protein, lactose, and energy) and anemia, regression models were constructed with and without adjustment for maternal age, parity, and time (days) postpartum. The same models were constructed using hemoglobin as a continuous predictor in lieu of dichotomous anemia to explore the role of hemoglobin levels and anemia severity in predicting milk outcomes. Results The group comparison indicated significantly higher milk protein and lower milk fat for anemic mothers relative to nonanemic counterparts. After adjustment for maternal age, parity, and time postpartum, maternal anemia was associated with significantly higher milk protein (P = 0.001) and significantly lower milk fat (P = 0.025). Hemoglobin had a significant inverse relationship with milk protein (P = 0.017) and a marginally significant positive relationship with milk fat (P = 0.060) after adjusting for the maternal variables. Neither anemia nor hemoglobin was significant in predicting lactose or milk energy. Conclusions Maternal anemia and hemoglobin concentration may be associated with complex changes in milk macronutrients. Future research should clarify the impact of maternal anemia on a range of breast milk components while accounting for other maternal characteristics.

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Background Infant feeding practices are rapidly changing within rural areas in Mexico, including indigenous communities. The aim of this study was to compare infant feeding recommendations between grandmothers and healthcare providers, to better understand the factors that may influence these practices within these communities. This study builds on research that recognizes the legacy of colonization as an ongoing process that impacts the lives of people through many pathways, including the substandard healthcare systems available to them. Methods Qualitative study based on secondary data analysis from interviews and focus groups guided by a socioecological framework conducted in 2018 in two rural, Indigenous communities in Central Mexico. Participants were purposively selected mothers (n = 25), grandmothers (n = 11), and healthcare providers (n = 24) who offered care to children up to two years of age and/or their mothers. Data were coded and thematically analyzed to contrast the different perspectives of infant feeding recommendations and practices between mother, grandmothers, and healthcare providers. Results Grandmothers and healthcare providers differed in their beliefs regarding appropriate timing to introduce non-milk foods and duration of breastfeeding. Compared to grandmothers, healthcare providers tended to believe that their recommendations were superior to those from people in the communities and expressed stereotypes reflected in negative attitudes towards mothers who did not follow their recommendations. Grandmothers often passed down advice from previous generations and their own experiences with infant feeding but were also open to learning from healthcare providers through government programs and sharing their knowledge with their daughters and other women. Given the contradictory recommendations from grandmothers and healthcare providers, mothers often were unsure which advice to follow. Conclusions There are important differences between grandmothers and healthcare providers regarding infant feeding recommendations. Healthcare providers may perceive their recommendations as superior given the neocolonial structures of the medical system. Public health policies are needed to address the different recommendations mothers receive from different sources, by harmonizing them and following an evidence-informed approach. Breastfeeding programs need to value and to seek the participation of grandmothers.