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1. 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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2. Variation in breast milk macronutrient contents by maternal anemia and hemoglobin concentration in northern Kenya

   https://doi.org/10.1002/ajhb.23238  

   Corbitt, Mary ; Paredes Ruvalcaba, Nerli ; Fujita, Masako ( March 2019 , American Journal of Human Biology)

   This study explored differing levels of macronutrients in breast milk in relation to maternal anemia and hemoglobin.

   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.

   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.

   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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3. 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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4. Bioactive factors in milk across lactation: Maternal effects and influence on infant growth in rhesus macaques ( Macaca mulatta )

   https://doi.org/10.1002/ajp.22544  

   Bernstein, Robin M. ; Hinde, Katie ( March 2016 , American Journal of Primatology)

   Among mammals, numerous bioactive factors in milk vary across mothers and influence offspring outcomes. This emerging area of research has primarily investigated such dynamics within rodent biomedical models, domesticated dairy breeds, and among humans in clinical contexts. Less understood are signaling factors in the milk of non‐human primates. Here, we report on multiple bioactive components in rhesus macaque (Macaca mulatta) milk and their associations with maternal and infant characteristics. Milk samples were collected from 59 macaques at multiple time points across lactation in conjunction with maternal and infant morphometrics and life‐history animal records. Milk was assayed for adiponectin (APN), epidermal growth factor (EGF) and its receptor (EGF‐R), and transforming growth factor beta 2 (TGF‐β₂). Regression models were constructed to assess the contributions of maternal factors on variation in milk bioactives, and on the relationship of this variation to infant body mass and growth. Maternal body mass, parity, social rank, and infant sex were all predictive of concentrations of milk bioactives. Primiparous mothers produced milk with higher adiponectin, but lower EGF, than multiparous mothers. Heavier mothers produced milk with lower EGF and EGF‐R, but higher TGF‐β₂. Mothers of daughters produced milk with higher TGF‐β₂. Mid‐ranking mothers produced milk with higher mean EGF and adiponectin concentrations than low‐ranking mothers. Milk EGF and EGF‐R were positively associated with infant body mass and growth rate. Importantly, these signaling bioactives (APN, EGF, EGF‐R, and TGF‐β₂) were significantly correlated with nutritional values of milk. The effects of milk signals remained after controlling for the available energy in milk revealing the added physiological role of non‐nutritive milk bioactives in the developing infant. Integrating analyses of energetic and other bioactive components of milk yields an important perspective for interpreting the magnitude, sources, and consequences of inter‐individual variation in milk synthesis. Am. J. Primatol. 78:838–850, 2016. © 2016 Wiley Periodicals, Inc.

    

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5. 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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