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1. Buffered or impaired: Maternal anemia, inflammation and breast milk macronutrients in northern Kenya

   https://doi.org/10.1002/ajpa.23752  

   Fujita, Masako ; Paredes Ruvalcaba, Nerli ; Wander, Katherine ; Corbitt, Mary ; Brindle, Eleanor ( December 2018 , American Journal of Physical Anthropology)

   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.

   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.

   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 predictedhigherfat (β = 0.655,p =.007 for IDA and β = 0.468,p =.092 for NIDA). NIDA predicted higher lactose (β = 1.020,p =.003).

   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 anemiaandinflammation). This study demonstrates the foundational importance of maternal micronutrient health and inflammation or infection for advancing the ecological understanding of human milk nutrient variation.

    

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2. Characterizing the extent human milk folate is buffered against maternal malnutrition and infection in drought‐stricken northern Kenya

   https://doi.org/10.1002/ajpa.24603  

   Fujita, Masako ; Wander, Katherine ; Tran, Tin ; Brindle, Eleanor ( August 2022 , American Journal of Biological Anthropology)

   Folate is an essential nutrient fundamental to human growth and development. Human milk maintains high folate content across the maternal folate status range, suggesting buffering of milk folate with prioritized delivery to milk at the expense of maternal depletion. We investigated whether and how the extent of this buffering may diminish under prolonged nutritional and/or disease stress, while taking into consideration infants' varying vulnerability to malnutrition‐related morbidity/mortality.

   A cross‐sectional study analyzed milk specimens from northern Kenyan mothers (n = 203), surveyed during a historic drought and ensuing food shortage. Multiple regression models for folate receptor‐α (FOLR1) in milk were constructed. Predictors included maternal underweight (BMI < 18.5), iron‐deficiency anemia (hemoglobin <12 g/dl and dried‐blood‐spot transferrin receptor >5 mg/L), folate deficiency (hyperhomocysteinemia, homocysteine >12 or 14 μmol/L), inflammation (serum C‐reactive protein >5 mg/L), infant age and sex, and mother‐infant interactions.

   In adjusted models, milk FOLR1 was unassociated with maternal underweight, iron‐deficiency anemia and inflammation. FOLR1 was positively associated with maternal folate deficiency, and inversely associated with infant age. There was interaction between infant age and maternal underweight, and between infant sex and maternal folate deficiency, predicting complex changes in FOLR1.

   Our results suggest that mothers buffer milk folate against their own nutritional stress even during a prolonged drought; however, the extent of this buffering may vary with infant age, and, among folate‐deficient mothers, with infant sex. Future research is needed to better understand this variability in maternal buffering of milk folate and how it relates to folate status in nursing infants.

    

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3. Maternal birth weight is associated with milk epidermal growth factor in Filipino women

   https://doi.org/10.1002/ajhb.23403  

   Kuziez, Duaa ; Harkey, Jamie ; Burack, Sarah ; Borja, Judith ; Quinn, Elizabeth A. ( February 2020 , American Journal of Human Biology)

   Lactational programming, through which milk‐borne bioactives influence both neonatal and long‐term biological development, is well established. However, almost no research has investigated how developmental stimuli during a mother's early life may influence her milk bioactives in adulthood. Here, we investigated the association between maternal birth weight and milk epidermal growth factor (EGF) and epidermal growth factor receptor (EGF‐R) in later life. We predicted there would be a decrease in both milk EGF and EGF‐R in the milk produced by mothers who were themselves born low birth weight.

   Study participants are from the Cebu Longitudinal Health and Nutrition Survey. Mothers (n= 69) were followed longitudinally since birth with prospective data collection. Anthropometrics, health, and dietary recalls were collected with early morning milk samples when mothers were 24 to 25 years of age. Milk samples were analyzed for EGF and its receptor (EGF‐R). Analysis of variance was used to test for differences in milk EGF and EGF‐R between low and average birthweight mothers after adjustment for parity, age, and maternal dietary energy intake.

   Mothers who were low birth weight produced milk with significantly less EGF and more EGF‐R which resulted in a lower ratio of EGF to EGF‐R. These associations persisted after adjustment for infant age, maternal adiposity, and dietary energy.

   While this is a small sample size, these preliminary findings suggest that maternal early life characteristics, such as birth weight, may be important contributors to variation in milk bioactives. Future work is necessary to understand how variation in maternal early life may influence milk composition in adulthood.

    

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4. Nutritional, inflammatory, and ecological correlates of maternal retinol allocation to breast milk in agro‐pastoral Ariaal communities of northern Kenya

   https://doi.org/10.1002/ajhb.22961  

   Fujita, Masako ; Lo, Yun‐Jia ; Brindle, Eleanor ( January 2017 , American Journal of Human Biology)

   Vitamin A (VA) is an essential micronutrient required for a range of biological functions throughout life. VA deficiency (VAD) claims an estimated 1 million preschool children's lives annually. Human milk is enriched with VA (retinol) from the maternal blood, which originates from the hepatic reserve and dietary intake. Secreting retinol into milk will benefit the nursing infant through breast milk, but retaining retinol is also important for the maternal health. Previous studies found that the public health intervention of high‐dose VA supplementation to lactating mothers did not significantly lower child mortality. The World Health Organization (WHO) recently acknowledged that our understanding about the principle of VA allocation within the maternal system and the secretion into milk is too incomplete to devise an effective intervention.

   We present a secondary analysis of data collected among lactating mothers in VAD endemic northern Kenya (n = 171), examining nutritional, inflammatory, and ecological factors that might associate with maternal retinol allocation. Regression models were applied using the outcome milk‐retinol allocation index: milk retinol/(milk retinol + serum retinol).

   Ten percent of the sample was identified as VAD. The average milk retinol concentration was 0.1 μmo/L, grossly below what is considered minimally necessary for an infant (1 μmol/L). VAD mothers and mothers with inflammation did not seem to compromise their milk retinol even though their serum retinol was lower than non‐VAD and noninflammation mothers. Breast milk fat concentration positively correlated with milk retinol but not with serum retinol.

   This exploratory study contributes toward an understanding of maternal retinol allocation.

    

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5. Chronic Stress Decreases Lactation Performance

   https://doi.org/10.1093/icb/icad044  

   Josefson, Chloe_C ; De Moura Pereira, Lucelia ; Skibiel, Amy_L ( May 2023 , Integrative And Comparative Biology)

   The ability to provision offspring with milk is a significant adaptive feature of mammals that allows for considerable maternal regulation of offspring beyond gestation, as milk provides complete nutrition for developing neonates. For mothers, lactation is a period of marked increases in energetic and nutritive demands to support milk synthesis; because of this considerable increase in demand imposed on multiple physiological systems, lactation is particularly susceptible to the effects of chronic stress. Here, we present work that explores the impact of chronic stress during lactation on maternal lactation performance (i.e., milk quality and quantity) and the expression of key milk synthesis genes in mammary tissue using a Sprague–Dawley rat model. We induced chronic stress using a well-established, ethologically relevant novel male intruder paradigm for 10 consecutive days during the postpartum period. We hypothesized that the increased energetic burden of mounting a chronic stress response during lactation would decrease lactation performance. Specifically, we predicted that chronic exposure to this social stressor would decrease either milk quality (i.e., composition of proximate components and energy density) or quantity. We also predicted that changes in proximate composition (i.e., lipid, lactose, and protein concentrations) would be associated with changes in gene expression levels of milk synthesis genes. Our results supported our hypothesis that chronic stress impairs lactation performance. Relative to the controls, chronically stressed rats had lower milk yields. We also found that milk quality was decreased; milk from chronically stressed mothers had lower lipid concentration and lower energy density, though protein and lactose concentrations were not different between treatment groups. Although there was a change in proximate composition, chronic stress did not impact mammary gland expression of key milk synthesis genes. Together, this work demonstrates that exposure to a chronic stressor impacts lactation performance, which in turn has the potential to impact offspring development via maternal effects.

    

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