Human Milk Cortisol Research Articles

Composition and Antioxidant Status of Human Milk of Women Living in Bydgoszcz (Poland).

The aim of this study was to compare cortisol concentrations, nutritional composition, and the antioxidant status of human milk of women living in Bydgoszcz (Poland), taking into account maternal factors (fertility, area of residence, economic activity, and breastfeeding period). The basic composition of human milk was evaluated using the MIRIS HMATM analyzer. The level of cortisol was determined by the enzyme-linked immunosorbent method. In order to determine the antioxidant activity, the DPPH radical method was used. It was observed that the concentration of cortisol in human milk in the group of women living in the city center was higher compared to the milk of women living on the outskirts of the city. In the group of women breastfeeding from 3 to 5 weeks after childbirth, the concentration of cortisol in milk was higher compared to the group of women breastfeeding less than 12 months of age and compared to the group of women lactating over 12 months of age. The antioxidant status of human milk was highest in the group of professionally active women and in the group of breastfeeding women from 3 to 5 weeks after childbirth. The basic composition and the caloric value of human milk differed statistically significantly in the study groups. Based on this study, it can be concluded that the composition and antioxidant status of human milk depends on maternal factors (fertility, professional activity, area of residence, and breastfeeding period). Higher cortisol concentrations in breast milk are probably determined by the area of residence (city center and associated higher noise/sound and stress levels) and lactation period (hormonal imbalance, fatigue, and postpartum period). Milk from economically active women shows greater protection against reactive oxygen species compared to milk from inactive women, protecting against the occurrence of diseases of civilization. Milk from breastfeeding women over 12 months of age also shows protection against reactive oxygen species, despite the fact that the highest level of antioxidant status of human milk occurs in the initial period of lactation.

Association between maternal stress and premature milk cortisol, milk IgA, and infant health: a cohort study.

Maternal stress is pervasive in the neonatal intensive care unit (NICU). Maternal stress is associated with changes in human milk (HM) immunomodulatory agents, which may impact neonatal health. We sought to determine the association between maternal stress, HM immunoglobulin A (IgA) and cortisol, and to assess how these milk components correlate with infant immune and neurodevelopmental outcomes. We then compared how these associations persist over time. The study design involved a cohort study of exclusively breastfeeding mothers and their singleton moderately preterm (28-34 weeks) infants admitted to the NICU. We collected maternal serum, maternal saliva, and first-morning whole milk samples, and administered maternal stress questionnaires at 1 and 5 weeks postpartum. We analyzed the samples for HM IgA (using a customized immunoassay in skim milk) and for HM and salivary cortisol (using a chemiluminescent immunoassay). Infant illness was assessed using the Score for Neonatal Acute Physiology II (SNAP II) and SNAP II with Perinatal Extension (SNAPPE II), and infant neurodevelopment were assessed using the Test of Infant Motor Performance. We analyzed changes in HM IgA and cortisol over time using paired t-tests. Furthermore, we performed correlation and regression analyses after adjusting for gestational age (GA), corrected GA, and infant days of life. In our study, we enrolled 26 dyads, with a mean maternal age of 28.1 years, consisting of 69% white, 19% Black, and 8% Hispanic. Cortisol: Salivary and HM cortisol were closely associated in week 1 but not in week 5. Though mean salivary cortisol remained stable over time [2.41 ng/mL (SD 2.43) to 2.32 (SD 1.77), p = 0.17], mean HM cortisol increased [1.96 ng/mL (SD 1.93) to 5.93 ng/mL (SD 3.83), p < 0.001]. Stress measures were inversely associated with HM cortisol at week 1 but not at week 5. IgA: HM IgA decreased over time (mean = -0.14 mg/mL, SD 0.53, p < 0.0001). High maternal stress, as measured by the Parental Stressor Scale: neonatal intensive care unit (PSS:NICU), was positively associated with HM IgA at week 5 (r = 0.79, P ≤ 0.001). Higher IgA was associated with a lower (better) SNAP II score at week 1 (r = -0.74, p = 0.05). No associations were found between maternal stress, salivary cortisol, HM cortisol, or HM IgA and neurodevelopment at discharge (as assessed using the TIMP score). Furthermore, these relationships did not differ by infant sex. Maternal stress showed associations with HM cortisol and HM IgA. In turn, HM IgA was associated with lower measures of infant illness.

Maternal stress is associated with higher protein-bound amino acid concentrations in human milk.

Maternal stress in the postpartum period affects not only the mother but also her newborn child, who is at increased risk of developing metabolic and mental disorders later in life. The mechanisms by which stress is transmitted to the infant are not yet fully understood. Human milk (HM) is a potential candidate as maternal stress affects various components of HM, e.g., fat and immunoglobulin concentrations. To date, it is unknown whether maternal stress also affects the amino acids (AAs) in HM, even though this nutrient is of extreme importance to child health and development. This study aimed to investigate whether and how maternal stress is associated with the AA composition of HM. In this observational cohort study (Amsterdam, The Netherlands), lactating women were recruited in two study groups: a high-stress (HS) group; women whose child was hospitalized (n = 24), and a control (CTL) group; women who gave birth to a healthy child (n = 73). HM was collected three times a day, on postpartum days 10, 17, and 24. Perceived psychological stress was measured using validated questionnaires, while biological stress measures were based on hair, saliva, and HM cortisol concentrations. HM protein-bound and free AAs were analyzed by liquid chromatography and compared between groups. Maternal perceived stress scores were higher in the HS group (p < 0.01). The concentrations of protein-bound AAs in HM were higher in the HS group compared to the CTL group (p = 0.028) and were positively associated with HM cortisol concentrations (p = 0.024). The concentrations of free AAs did not differ between study groups and were unrelated to cortisol concentrations. Findings from this prospective cohort study suggest that maternal stress in the postpartum period is associated with an altered human milk amino acid composition, which could play a role in the transmission of maternal stress effects to her child. The physiological implications of these stress-induced changes for infant development await future research.

The Relationship of Preterm, Term, and Post-Term Births to Maternal Stress and Human Milk Cortisol Levels.

Introduction: Maternal stress can lead to changes in the composition of human breast milk. The present study evaluates cortisol levels in the breast milk of mothers after giving birth preterm, term, or post-term, and ascertains whether the levels are associated with maternal stress. Materials and Methods: Included in the study were mothers who gave birth vaginally after 32 weeks of gestation between January and April 2022. The breast milk was expressed with an electronic pump under the supervision of a nurse on day 7 following birth, and 2 mL samples of the milk were transferred into microtubes and stored at -80°C. Stress in the mothers was measured using the perceived stress scale developed by Cohen et al. The human breast milk cortisol levels were determined using an enzyme-linked immunoassay in a single session. Results: A total of 90 mothers, including 30 with preterm births, 38 with term births, and 22 with post-term births, were included in the study. The median stress scale score was 28 (17-50) and the median breast milk cortisol level was 0.49 ng/mL (0.1-1.96 ng/mL). A significant positive correlation was noted between the stress scale scores and breast milk cortisol levels (r = 0.56, p < 0.01). The breast milk cortisol levels and maternal stress scale scores were significantly higher in the preterm birth group than in the term birth group (p = 0.011 and p = 0.013, respectively). Conclusion: Although there is an association between maternal stress and preterm labor and milk cortisol levels, we believe that more studies are needed to establish a causal link.

Associations between maternal socioeconomic, psychosocial and seasonal factors, infant characteristics and human milk cortisol concentrations.

Glucocorticoids are one component of human milk (HM) potentially affecting offspring development. Previous studies have identified various maternal, obstetric and socioeconomic characteristics that are associated with HM cortisol concentration but the literature is still scarce concerning these determinants in human populations. We aimed to identify which factors are linked with HM cortisol concentration at 2months postpartum. We analyzed data from 340 lactating Finnish mothers using ordinary least squares regression with log-transformed HM cortisol concentration as the dependent variable. Potential predictors included obstetric and maternal factors (maternal age, parity status, delivery mode, gestational age, pre-pregnancy obesity, and smoking in pregnancy), socioeconomic status (education and socioeconomic class), subjective economic well-being, maternal psychosocial factors (postpartum depression and anxiety symptoms), infant sex and age, and HM sample characteristics (time of the day and season of the year at sample collection). The strongest and most robust predictors were season of the year of sample collection and parity status. HM cortisol concentration was significantly higher for primiparas than multiparas. HM samples collected in summer showed significantly higher cortisol concentrations than those collected in winter, spring or autumn. The findings suggest that parity and season of the year at sample collection may be important factors to control for when examining HM cortisol. The strongest and most robust associations were related to maternal and sample characteristics and not to socioeconomic and psychosocial distress. This may be related to the fact that the study was conducted in a low-risk population.

Human Milk Glucocorticoid Levels Are Associated With Infant Adiposity and Head Circumference Over the First Year of Life.

Human milk (HM) is a complex and dynamic biological fluid, which contains appreciable concentrations of the glucocorticoids, cortisol and cortisone. Experimental studies in non-human primates suggest the HM glucocorticoids' impact on infant growth and body composition. In this current study, analysis is made of the relationships between HM glucocorticoid concentrations and the infant growth and development over the first year of life. HM was collected by lactating healthy women (n = 18), using a standardized protocol, at 2, 5, 9, and 12 months after childbirth. Cortisol and cortisone concentrations in the HM were measured using liquid chromatography mass spectrometry. Infant weight, length and head circumference were measured by standard protocols and percentage fat mass (% FM) determined by whole body bioimpedance. Cortisol and cortisone concentrations were unaltered over the analyzed lactation period (2–12 months), and were altered by infant sex. Although, HM cortisol was positively associated with infant percentage fat mass (% FM) (p = 0.008) and cortisone positively associated with infant head circumference (p = 0.01). For the first 12 months of life, the concentration of HM glucocorticoids levels was positively associated with infant adiposity (%FM) and head circumference. This preliminary evidence provides insight to a possible relationship between ingested HM glucocorticoids and infant body composition. Further studies are required to determine the mechanisms regulating HM glucocorticoids.

Interactions between cortisol and lipids in human milk

BackgroundHuman breast milk is one of the key early postnatal biological exposures for the developing child. It includes bioactive compounds, such as cortisol and fatty acids, which may be linked via the mother’s lipid metabolism.MethodsThis study investigated the associations between cortisol and lipids in human milk at the infant age of 2.5 months. Human milk cortisol concentrations were measured using luminescence immunoassay, and two groups of milks (n = 50 each) were formed based on either high (> 10 nmol/L) or low (< 3 nmol/L) cortisol levels. Lipids, as fatty acid content and composition of neutral (triacylglycerol-rich) and polar (phospholipid-rich) lipids, were measured with gas chromatography. The samples originated from the FinnBrain Birth Cohort Study.ResultsThe percentage of phospholipid-rich lipids of total lipids was 33.08% ± 1.33%. In triacylglycerol-rich lipids, high cortisol level in milk was associated with higher lauric (12:0, mass % and mg/mL), myristic (14:0, mass % and mg/mL), eicosenoic (20:1n − 9, mass %), docosenoic (22:1n − 9, mass %, and mg/mL) acids, and to lower palmitic acid (16:0, mass %) compared with low cortisol levels in milk. In phospholipid-rich lipids, high cortisol level was associated with higher myristic (14:0, mass %) and docosenoic (22:1n − 9, mass %) acids. After adjusting for pre-pregnancy BMI and sampling time by linear regression, the milk cortisol remained a significant predictor for lauric and myristic acids in triacylglycerol-rich lipids, and myristic and docosenoic acid in phospholipid-rich lipids (β = 0.23 to 0.38 and p < 0.05 for each).ConclusionsThis study revealed certain significant associations between milk cortisol and the fatty acid composition of human milk, indicating that cortisol might be one of the factors affecting the origin of the lipids in human milk.

Human milk cortisol and immune factors over the first three postnatal months: Relations to maternal psychosocial distress.

Many biologically active factors are present in human milk including proteins, lipids, immune factors, and hormones. The milk composition varies over time and shows large inter-individual variability. This study examined variations of human milk immune factors and cortisol concentrations in the first three months post-partum, and their potential associations with maternal psychosocial distress. Seventy-seven healthy mothers with full term pregnancies were enrolled, of which 51 mothers collected morning milk samples at 2, 6 and 12 weeks post-delivery. Maternal psychosocial distress was assessed at 6 weeks post-delivery using questionnaires for stress, anxiety, and depressive symptoms. Immune factors were determined using multiplex immunoassays and included innate immunity factors (IL1β, IL6, IL12, IFNγ, TNFα), acquired immunity factors (IL2, IL4, IL10, IL13, IL17), chemokines (IL8, Groα, MCP1, MIP1β), growth factors (IL5, IL7, GCSF, GMCSF, TGFβ2) and immunoglobulins (IgA, total IgG, IgM). Cortisol was quantified using liquid chromatography-tandem mass spectrometry. A linear mixed effects model was fit to test whether stress, anxiety, and depressive symptoms individually predicted human milk cortisol concentrations after accounting for covariates. Repeated measurement analyses were used to compare women with high (n = 13) versus low psychosocial distress (n = 13) for immune factors and cortisol concentrations. Virtually all immune factors and cortisol, with the exception of the granulocyte-macrophage colony-stimulating factor (GMCSF), were detected in the human milk samples. The concentrations of the immune factors decreased during the first 3 months, while cortisol concentrations increased over time. No correlation was observed between any of the immune factors and cortisol. No consistent relationship between postnatal psychosocial distress and concentrations of immune factors was found, whereas higher psychosocial distress was predictive of higher cortisol concentrations in human milk. In the current study we found no evidence for an association between natural variations in maternal distress and immune factor concentrations in milk. It is uncertain if this lack of association would also be observed in studies with larger populations, with less uniform demographic characteristics, or with women with higher (clinical) levels of anxiety, stress and/or depressive symptoms. In contrast, maternal psychosocial distress was positively related to higher milk cortisol concentrations at week 2 post-delivery. Further investigation on maternal psychosocial distress in relation to human milk composition is warranted.

Human milk cortisol concentration predicts experimentally induced infant fear reactivity: moderation by infant sex.

Little consideration has been given to the possibility of human infant development being shaped via lactocrine programming, and by breast milk cortisol levels specifically. Despite animal models indicating that glucocorticoid (GC) exposure via lactation might modify brain development and behavior, only one study has reported that milk cortisol levels were positively associated with infant negative affectivity, especially fearfulness and sadness-early emerging risk factors for internalizing difficulties such as anxiety. The aim of the current study was to investigate whether human milk cortisol is associated with mother-reported fearfulness and experimentally induced infant fear reactivity. Mother-infant dyads (n = 65) enrolled in the FinnBrain Cohort Study participated. Breast milk samples were obtained 2.5 months postpartum, and milk cortisol concentrations were ascertained using validated luminescence immunoassay methodology. Infant fear reactivity was assessed using maternal reports 6 months postpartum and in a laboratory 8 months postpartum. There was a significant interaction between infant sex and milk cortisol such that higher milk cortisol was related to higher infant fear reactivity in a laboratory setting in girls (β = 0.36, p = .04) but not in boys (β = -0.15, p = .40). Milk cortisol was not associated with mother-reported infant fearfulness. Results suggest that higher human milk cortisol concentrations are associated with elevated experimentally induced fear in infancy. Findings support lactocrine programming, and suggest that mothers may "communicate" vital information about stressful environments via cortisol contained in breast milk, shaping girls' early emotional reactivity.

Variation of Human Milk Glucocorticoids over 24 hour Period

Human milk (HM) contains a complex array of hormones, including members of the glucocorticoid family. The predominant glucocorticoids, cortisol and cortisone may influence the growth and behaviour of the breastfed infant. However, little is understood of the factors regulating the levels of these hormones within HM. The aim of the study was to examine HM cortisol and cortisone concentration, measured in samples collected at each feed during a 24hour period. Twenty three exclusively breastfeeding mothers collected milk, prior to and after each breastfeeding session over 24hour period at 3.2(1.60) months. HM cortisol and cortisone levels were measured using high pressure liquid chromatography mass spectroscopy. Cortisone was the predominant glucocorticoid (3.40ng/ml), and cortisol was detected in all samples (1.62ng/ml). A positive correlation was found between cortisone and cortisol (r=0.61, y=1.93±0.24, p<0.0001). Cortisol and cortisone concentrations were significantly higher in feeds in the morning (2.97ng/ml and 4.88ng/ml), compared to afternoon (1.20ng/ml and 3.54ng/ml), evening (0.69ng/ml and 2.13ng/ml) and night (1.59 and 3.27ng/ml). No difference was found between glucocorticoids level of the milk expressed for collection either before or immediately after the breastfeed, or between milk collected from the left or right breast. This study shows that HM glucocorticoid concentrations exhibit a 24hour pattern, with highest peak levels in the early morning, reflecting the circadian pattern as previously reported in plasma. Thus, HM glucocorticoid concentrations are likely to reflect those in the maternal circulation.

Cortisol in human milk predicts child BMI.

Breastfeeding has been linked to lower rates of childhood obesity. Human milk contains cortisol, known to regulate glucose storage and metabolism. The aim of this study was to to test the hypothesis that early exposure to cortisol in human breast milk helps to modulate infant body mass index (BMI) trajectories over the first 2 years of life. Growth curve modeling was used to examine whether infant exposure to cortisol in human milk at 3 months predicted changes in child body mass index percentile (BMIP) at 6, 12, and 24 months of age in 51 breastfeeding mother-child pairs. Infants exposed to higher milk cortisol levels at 3 months were less likely to exhibit BMIP gains over the first 2 years of life, compared with infants exposed to lower milk cortisol. By age 2, infants exposed to higher milk cortisol levels had lower BMIPs than infants exposed to lower milk cortisol. Milk cortisol was a stronger predictor of BMIP change in girls than boys. Cortisol exposure through human milk may help to program metabolic functioning and childhood obesity risk. Further, because infant formula contains only trace amounts of glucocorticoids, these findings suggest that cortisol in milk is a novel biological pathway through which breastfeeding may protect against later obesity.

Correlation between maternal and infant cortisol varies by breastfeeding status

ObjectiveThe objective of this study was to examine associations of mother and infant salivary cortisol, measured three times over the course of a day, and assess whether these varied by breastfeeding status. MethodsWe conducted a cross-sectional study of 54 mothers and their infants aged 4–11 months. Mothers collected their own saliva and that of their infants upon awakening, 30min after waking and at bedtime. Breastfeeding status was reported by mothers and cortisol level was measured in saliva in μg/dl using standard techniques. We used generalized linear models to evaluate relationships between maternal and infant cortisol levels, and assessed whether the relationship differed by breastfeeding status: formula only compared to partial and full breastfeeding, adjusting for infant sex, race, age, maternal education, and family income. ResultsThirty-four infants received formula only and 20 were either partially or fully breastfed. Breastfeeding was associated with higher household income, higher maternal education, and white race. Cortisol levels were higher among breastfed infants at all three time points. After adjustment, maternal cortisol levels were related with infant cortisol at bedtime only (regression estimate 0.06; 95% CI: 0.10, 1.1; p=0.02). The adjusted association between bedtime maternal and infant cortisol was stronger among breastfeeding dyads than among formula-feeding dyads (regression estimate 1.0; 95% CI: 0.1, 2.0; p=0.04 vs. 0.6; CI: −0.1, 1.3; p=0.10). In addition, we assessed the influence of maternal education and household income in our adjusted model; income strengthened the observed association, whereas maternal education did not change the estimate. ConclusionsBreastfeeding mothers and infants had significant correlations for cortisol at bedtime, while formula-feeding dyads did not. These data suggest that several factors may contribute to cortisol synchrony observed in mother/infant dyads, including the transfer of cortisol in human milk, physical interaction such as skin-to-skin contact, and shared environment. In addition, our findings support household income as a possible contributor.

Human milk cortisol is associated with infant temperament

The implications of the biologically active elements in milk for the mammalian infant are largely unknown. Animal models demonstrate that transmission of glucocorticoids through milk influences behavior and modifies brain development in offspring. The aim of this study was to determine the relation between human milk cortisol levels and temperament of the breastfed infant. Fifty-two mother and infant pairs participated when the infants were three-months old. Milk cortisol levels were assessed and each mother completed the Infant Behavior Questionnaire (IBQ), a widely used parent-report measure of infant temperament. Analyses revealed a positive association between milk cortisol and the negative affectivity dimension of the IBQ (partial r=.37, p<.01). No correlation was found between elevated cortisol levels and the surgency/extraversion or the orienting/regulation dimensions. Further, the positive association between increased maternal milk cortisol and negative affectivity was present among girls (β=.59, p<.01), but not among boys. (Although, the sex by milk cortisol interaction term was not statistically significant, suggesting that these results require replication.) Environmental factors such as maternal demographics and negative maternal affect (depression and perceived stress) at the time of assessment did not account for the positive association. The findings support the proposal that exposure to elevated levels of cortisol in human milk influences infant temperament. The findings further suggest that mothers have the ability to shape offspring phenotype through the transmission of biologically active components in milk.

Identification of corticosteroid-binding globulin in human milk: measurement with a filter disk assay.

We have studied the concentration and properties of a protein which binds cortisol in human milk in samples obtained from women during the first 100 days after delivery. A filter disk assay was developed both for the measurement of plasma corticosteroid-binding globulin (CBG) and for the cortisol-binding protein in milk. The concentration of CBG in milk, expressed as its capacity to bind cortisol, is highest on the day of delivery, ca, 0.80 mug/dl, falls over the next 10 days to ca. 0.25 mug/dl, and remains at that level thereafter. If the concentration of CBG is expressed relative to the concentration of serum albumin in milk, it increases from day 1 to day 3 and then remains constant. A detailed comparison of CBG derived from milk and plasma showed that the two proteins co-migrated on Sephadex, sucrose gradient ultracentrifugation, and polyacrylamide gel electrophoresis. The two proteins had the same affinity for cotrisol, progesterone, 17-OH-progesterone, and dexamethasone. Furthermore, the binding activity of CBG in milk was neutralized with anti-CBG antibodies raised against CBG isolated from plasma. Unlike CBG, the concentration of cortisol in milk, 0.8-3.5 mug/dl, showed no systematic variation as a function of the postpartum day on which the sample was obtained.