Circadian variations in fat content of expressed breast milk from mothers of preterm infants

Role of lipidomics in assessing the functional lipid composition in breast milk

Breast milk is the ideal source of nutrients for infants in early life. Lipids represent 2–5% of the total breast milk composition and are a major energy source providing 50% of an infant’s energy intake. Functional lipids are an emerging class of lipids in breast milk mediating several different biological functions, health, and developmental outcome. Lipidomics is an emerging field that studies the structure and function of lipidome. It provides the ability to identify new signaling molecules, mechanisms underlying physiological activities, and possible biomarkers for early diagnosis and prognosis of diseases, thus laying the foundation for individualized, targeted, and precise nutritional management strategies. This emerging technique can be useful to study the major role of functional lipids in breast milk in several dimensions. Functional lipids are consumed with daily food intake; however, they have physiological benefits reported to reduce the risk of disease. Functional lipids are a new area of interest in lipidomics, but very little is known of the functional lipidome in human breast milk. In this review, we focus on the role of lipidomics in assessing functional lipid composition in breast milk and how lipid bioinformatics, a newly emerging branch in this field, can help to determine the mechanisms by which breast milk affects newborn health.

Carbohydrate content of human milk is affected by seasonal variations: a retrospective observational study

OBJECTIVE

The influence of seasonal variation upon human milk macronutrient content has not been elucidated. This study aimed to compare the macronutrient content of HM produced by lactating mothers during the winter and the summer seasons.

STUDY DESIGN

Macronutrient content of colostrum milk samples collected from lactating mothers of healthy term infants between March 2012 and February 2016 was measured by mid-infrared spectroscopy and compared.

RESULT

The carbohydrate content of the colostrum was significantly higher in the summer season than in the winter season (6.2 ± 1.3 vs. 5.5 ± 1.4, p-value < 0.001). Protein, fat, and energy contents were similar in summer and winter in both groups (protein 2.7 ± 2.1 vs. 2.6 ± 2.2 g/100 ml, fat 2.6 ± 1.9 vs. 2.35 ± 1.9 g/100 ml, and energy 62 ± 19.1 vs. 60.5 ± 21 kcal/100 ml, respectively).

CONCLUSION

The carbohydrate content in colostrum obtained from mothers of term infants was affected by seasonal variations.

Human Milk Metabolic Hormones: Analytical Methods and Current Understanding

Human milk (HM) contains a wide array of peptide hormones including leptin and adiponectin, which are involved in the regulation of infant growth and development. These essential hormones might play an important role in the regulation of metabolic reprogramming of the new-born infant. However, HM hormone studies are sparse and heterogeneous in regard to the study design, sample collection, preparation and analysis methods. This review discussed the limitations of HM hormone analysis highlighting the gaps in pre-analytical and analytical stages. The methods used to quantify HM metabolic hormones (leptin, adiponectin, ghrelin, insulin, obestatin, resistin and apelin) can be classified as immunoassay, immunosensor and chromatography. Immunoassay methods (ELISA and RIA) have been predominantly used in the measurement of these HM hormones. The relative validity parameters of HM hormones analysis are often overlooked in publications, despite the complexity and differences of HM matrix when compared to that of plasma and urine. Therefore, appropriate reports of validation parameters of methodology and instrumentation are crucial for accurate measurements and therefore better understanding of the HM metabolic hormones and their influences on infant outcomes.

Chrononutrition and Breast Milk: A Review of Circadian Variation in Breast Milk Nutrient Composition

Objective

The objective of this literature review was to identify and summarize the current knowledge on the circadian variation of breast milk nutrients and the implications of these findings.

Method

A review of literature was conducted, including all relevant studies regardless of location and year of publication.

Results

The amino acids tyrosine, histidine, aspartic acid and phenylalanine and energy were observed to be higher during the day. Fat and the vitamins B-1, B-2, B-3, B-6, and B-12 were higher at night. Other studies have shown conflicting results or no circadian variation for certain nutrients. Poor reproducibility and small sample sizes affect the quality of existing research.

Conclusion

More research is needed, and longitudinal studies would help assess the effect of breast milk chrononutrition on the long-term health outcomes of infants.

Nutritional and Non-nutritional Composition of Human Milk Is Modulated by Maternal, Infant, and Methodological Factors

Human milk (HM) is dynamic and shows a high inter- and intra-individual variability. To characterize HM with precision, it is necessary to understand the factors that modulate its composition. The objective of this narrative review is to summarize the maternal, infant and methodological factors that affect HM composition. We searched SCOPUS and PubMed databases for articles related to factors that are known to or could potentially influence HM composition and volume across lactation periods. Our comprehensive review encompasses various maternal-, infant-related, and methodological factors that modulate aspects of HM composition including macro- and micronutrients, vitamins and minerals, as well as volume. The most profound changes were observed in HM lipids and lipophiles. Evidence exists for many of the infant-related factors known to affect the nutritive and non-nutritive components of HM (e.g., birth weight, gestational age, infant age/stage of lactation). In contrast, less is known with respect to maternal factors; where there is either limited research or conflicting evidence (e.g., maternal lifestyle, obstetric history, medical conditions), except for the mother's diet, for which there is a relatively well-established understanding. Equally, although many of the methodological factors (e.g., HM sampling, handling and analytics) are known to impact HM composition, few studies have investigated this as a primary outcome, making it an important area of future research in HM. Here we propose a systematic capture of numerous maternal- and infant-related characteristics to facilitate associative comparisons of HM data within and across studies. Additionally, it would be prudent to standardize the methodological aspects known to affect HM composition in analytics, not only for HM lipids and lipophiles, but also for those nutrients whose variability is yet less well-understood. Defining the factors determining HM composition with accuracy will open perspectives for maternal intervention to optimize milk composition for specific needs of infants.

The Effect of Infant's Sex on Human Milk Macronutrients Content: An Observational Study

Background: Sex differences in infant mortality and neonatal morbidity have been previously documented. Few studies, with conflicting results, have investigated the interaction between human milk (HM) macronutrients and energy content and infant sex. Objective: To test the null hypothesis that HM macronutrients content will not be affected by infant's sex. Materials and Methods: We compiled previously generated data on macronutrients content of colostrum samples and mature milk samples collected from lactating mothers of healthy term infants. Macronutrient content was measured using mid-infrared spectroscopy. Results: A total of 324 milk samples were included in the analysis consisting of 189 colostrum and 135 mature milk samples. There were 92 female and 97 male infants in the colostrum group and 65 female and 70 male infants in the mature milk group. Maternal age, gestational age, mode of delivery and percentage of large for gestational age, small for gestational age, and appropriate for gestational age were similar between female and male groups at all stages of lactation. Birth weight in male infants was significantly higher than in female infants (3389.5 ± 444.6 versus 3229.2 ± 415 g, p = 0.016). There were no statistically significant differences in macronutrient contents between the female and male groups at all stages studied. Conclusion: Macronutrients and energy content in colostrum and mature milk collected from mothers of term infants were unaffected by the sex of their offspring.

Circadian Variation in Human Milk Composition, a Systematic Review

Background: Breastfeeding is considered the most optimal mode of feeding for neonates and mothers. Human milk changes over the course of lactation in order to perfectly suit the infant’s nutritional and immunological needs. Its composition also varies throughout the day. Circadian fluctuations in some bioactive components are suggested to transfer chronobiological information from mother to child to assist the development of the biological clock. This review aims to give a complete overview of studies examining human milk components found to exhibit circadian variation in their concentration. Methods: We included studies assessing the concentration of a specific human milk component more than once in 24 h. Study characteristics, including gestational age, lactational stage, sampling strategy, analytical method, and outcome were extracted. Methodological quality was graded using a modified Newcastle-Ottawa Scale (NOS). Results: A total of 83 reports assessing the circadian variation in the concentration of 71 human milk components were included. Heterogeneity among studies was high. The methodological quality varied widely. Significant circadian variation is found in tryptophan, fats, triacylglycerol, cholesterol, iron, melatonin, cortisol, and cortisone. This may play a role in the child’s growth and development in terms of the biological clock.

Circadian changes in the composition of human milk macronutrients depending on pregnancy duration: a cross-sectional study

Background

The purpose of this study was to evaluate the circadian variation of human milk macronutrients and energy content depending upon pregnancy duration.

Methods

One hundred eighty fresh human milk samples from 45 mothers (27 of preterm and 18 of full-term newborns) were collected on a single day chosen between the 14th to 16th day after delivery. The samples were taken four times per day at 12 PM, 6 PM, 12 AM and 6 AM. Only lactating women, who could not breastfeed their hospitalized newborns and expressed milk by breast pump, were enrolled in the study. Human milk macronutrient composition and energy count were evaluated by mid-infrared spectrophotometry.

Results

Significant differences in macronutrient content were observed between 6 AM and 12 PM for mean protein content (t = − 4.62, df = 44, p < 0.001), for mean fat content (t = − 2.10, df = 44, p = 0.04) and for mean energy content (t = − 2.24, df = 44, p = 0.03); between 6 AM and 6 PM for mean protein content (t = − 2.41, df = 43, p = 0.02), for mean fat content (t = − 3.76, df = 43, p = 0.001) and for mean energy content (t = − 3.85, df = 43, p < 0.001); between 12 PM and 12 AM for mean protein content (Wilcoxon test V = 75.5, p = 0.001), for mean fat content (t = 2.50, df = 44, p = 0.02) and for mean energy content (t = 2.74, df = 44, p = 0.01); between 6 PM and 12 AM for mean protein content (V = 229, p = 0.02), for mean fat content (t = 4.39, df = 43, p < 0.001) and for mean energy content (t = − 4.57, df = 43, p < 0.001). The average content of carbohydrates did not change significantly during the 24 h. The samples of preterm newborns’ mothers had more apparent diurnal fluctuations in macronutrient content.

Conclusions

Our study revealed significant diurnal variations in protein and fat in human milk, and these circadian fluctuations were more apparent in the milk of mothers of preterm infants.

Helping Mom Help Baby: Nutrition-Based Support for the Mother-Infant Dyad During Lactation

Lactation and breastfeeding support the short- and long-term health of both mother and infant, yet the success of these processes depend upon individual and combined factors of the pair. Complications during pregnancy and delivery greatly affect the likelihood that a mother will be capable of breastfeeding for at least the recommended 6 months. Guidelines for women regarding postpartum diet and lifestyle management also fail to reflect the diversity of mother-infant pairs and their circumstances. In our analysis of the literature, we have identified a categorical deficit in modern scientific discourse regarding human lactation; namely, that postpartum involves full-body contribution of resources and thus requires the application of nutrition from a systemic perspective.

Current Practice in Untargeted Human Milk Metabolomics

Human milk (HM) is considered the gold standard for infant nutrition. HM contains macro- and micronutrients, as well as a range of bioactive compounds (hormones, growth factors, cell debris, etc.). The analysis of the complex and dynamic composition of HM has been a permanent challenge for researchers. The use of novel, cutting-edge techniques involving different metabolomics platforms has permitted to expand knowledge on the variable composition of HM. This review aims to present the state-of-the-art in untargeted metabolomic studies of HM, with emphasis on sampling, extraction and analysis steps. Workflows available from the literature have been critically revised and compared, including a comprehensive assessment of the achievable metabolome coverage. Based on the scientific evidence available, recommendations for future untargeted HM metabolomics studies are included.

Macronutrient analysis of preterm human milk using mid-infrared spectrophotometry

Background Human milk is the optimal source of nutrition for preterm infants. However, breast milk alone is often not sufficient to satisfy the high nutritional needs for growth and development in preterm infants. Fortified human breast milk is the best way to meet the nutritional needs of preterm infants. Human breast milk is fortified according to the estimated nutrient content of mature breast milk; however, because the content of breast milk is highly variable, the macronutrient support may be more or less than needed. The goal of this study was to analyze the macronutrient content of preterm human milk during the first 6 weeks of lactation. Methods The study included 32 mothers of preterm infants with a gestational age of ≤32 weeks. Breast milk was collected in 24-h cycles and analyzed daily using mid-infrared (MIR) spectroscopy. We measured protein, fat and lactose concentrations in the breast milk, and the energy content was calculated. Results The protein content was high during the first weeks of lactation, but decreased as lactation progressed. The fat, energy and lactose contents of the breast milk were low during the first 2 weeks of lactation, increased as lactation progressed and remained constant thereafter. In women with high body mass index (BMI), higher protein levels were found in transitional milk. In women who had high income level, higher fat and energy levels were found in transitional milk. Conclusion Our findings indicate that the macronutrient content of preterm breast milk changes throughout the course of lactation, with BMI and income level. Knowledge of the macronutrient composition of breast milk is necessary to ensure that preterm infants receive the appropriate types and quantities of nutrients to promote optimal growth, and to ensure that breast milk is fortified according to individual needs. Our findings may be useful for the provision of optimal nutritional support for preterm infants.

Chronotype: Implications for Epidemiologic Studies on Chrono-Nutrition and Cardiometabolic Health

Chrono-nutrition is an emerging research field in nutritional epidemiology that encompasses 3 dimensions of eating behavior: timing, frequency, and regularity. To date, few studies have investigated how an individual's circadian typology, i.e., one's chronotype, affects the association between chrono-nutrition and cardiometabolic health. This review sets the directions for future research by providing a narrative overview of recent epidemiologic research on chronotype, its determinants, and its association with dietary intake and cardiometabolic health. Limited research was found on the association between chronotype and dietary intake in infants, children, and older adults. Moreover, most of the evidence in adolescents and adults was restricted to cross-sectional surveys with few longitudinal cohorts simultaneously collecting data on chronotype and dietary intake. There was a gap in the research concerning the association between chronotype and the 3 dimensions of chrono-nutrition. Whether chronotype modifies the association between diet and cardiometabolic health outcomes remains to be elucidated. In conclusion, further research is required to understand the interplay between chronotype, chrono-nutrition, and cardiometabolic health outcomes.

Temporal variations of nucleosides and nucleotides in rabbit milk

Nucleotides and nucleosides have a preeminent role in physiological and biochemical processes for newborns, the major source of these during early development is the breast milk. Different biomolecules exhibit daily fluctuations in maternal milk that could transfer temporal information that synchronize newborn circadian system. As a first approach, we characterized the diurnal profile of nucleotides and nucleosides contained in maternal milk of rabbits during the first week of lactation. It is possible that some nucleosides, such as adenosine, play a relevant role in setting up the emerging circadian rhythmicity, whereas uridine and guanosine could participate in the maintenance of rhythmicity.

Human Milk Lipidomics: Current Techniques and Methodologies

Human milk contains a complex combination of lipids, proteins, carbohydrates, and minerals, which are essential for infant growth and development. While the lipid portion constitutes only 5% of the total human milk composition, it accounts for over 50% of the infant’s daily energy intake. Human milk lipids vary throughout a feed, day, and through different stages of lactation, resulting in difficulties in sampling standardization and, like blood, human milk is bioactive containing endogenous lipases, therefore appropriate storage is critical in order to prevent lipolysis. Suitable sample preparation, often not described in studies, must also be chosen to achieve the aims of the study. Gas chromatography methods have classically been carried out to investigate the fatty acid composition of human milk lipids, but with the advancement of other chromatographic techniques, such as liquid and supercritical fluid chromatography, as well as mass spectrometry, intact lipids can also be characterized. Despite the known importance, concise and comprehensive analysis of the human milk lipidome is limited, with gaps existing in all areas of human milk lipidomics, discussed in this review. With appropriate methodology and instrumentation, further understanding of the human milk lipidome and the influence it has on infant outcomes can be achieved.

Breast Milk Lipidome Is Associated with Early Growth Trajectory in Preterm Infants

Human milk is recommended for feeding preterm infants. The current pilot study aims to determine whether breast-milk lipidome had any impact on the early growth-pattern of preterm infants fed their own mother's milk. A prospective-monocentric-observational birth-cohort was established, enrolling 138 preterm infants, who received their own mother's breast-milk throughout hospital stay. All infants were ranked according to the change in weight Z-score between birth and hospital discharge. Then, we selected infants who experienced "slower" (n = 15, -1.54 ± 0.42 Z-score) or "faster" (n = 11, -0.48 ± 0.19 Z-score) growth; as expected, although groups did not differ regarding gestational age, birth weight Z-score was lower in the "faster-growth" group (0.56 ± 0.72 vs. -1.59 ± 0.96). Liquid chromatography-mass spectrometry lipidomic signatures combined with multivariate analyses made it possible to identify breast-milk lipid species that allowed clear-cut discrimination between groups. Validation of the selected biomarkers was performed using multidimensional statistical, false-discovery-rate and ROC (Receiver Operating Characteristic) tools. Breast-milk associated with faster growth contained more medium-chain saturated fatty acid and sphingomyelin, dihomo-γ-linolenic acid (DGLA)-containing phosphethanolamine, and less oleic acid-containing triglyceride and DGLA-oxylipin. The ability of such biomarkers to predict early-growth was validated in presence of confounding clinical factors but remains to be ascertained in larger cohort studies.

Circadian Variation of Breast Milk Components and Implications for Care

Several components of breast milk show circadian variability. It is likely that at least some of these macronutrients, hormones, and micronutrients produce circadian stimuli that enhance the well-being of breast-fed infants. Future research should determine whether high-risk infants benefit if breast milk is given during the same circadian phase as it was expressed.

Preterm Human Milk Macronutrient and Energy Composition: A Systematic Review and Meta-Analysis

This study is a systematic review of the macronutrient and energy composition of preterm human milk to enable the practicing neonatologist to make informed nutritional decisions in preterm infants. Meta-analyses were conducted in all the studies that reported total energy, true protein, fat, and lactose. Protein content decreased massively (by one-half) and significantly from day 1 to 3 at week 10 to 12. There was a significant linear increase in fat, lactose, and energy content during the same timeframe. Theoretic calculations on energy and macronutrient intake of preterm infants must be made according to a lactation time-specific manner.

Retinol, α-tocopherol, and selected minerals in breast milk of lactating women with full-term infants in South Korea

BACKGROUND/OBJECTIVES

This study was performed to measure fat-soluble vitamins and minerals in breast milk of Korean lactating mothers who exclusively breastfed their babies.

SUBJECTS/METHODS

Breast milk samples were collected from 334 mothers. Concentrations of retinol and α-tocopherol were analyzed by high performance liquid chromatography ultraviolet spectrometry while concentrations of minerals were measured by inductively coupled plasma optical emission spectrometry.

RESULTS

Retinol and α-tocopherol contents of breast milk were 39.58 ± 19.64 µg/dL and 0.23 ± 0.13 mg/dL, respectively. Average sodium, potassium, calcium, phosphorus, and magnesium levels in breast milk were 11.11 ± 5.16, 38.56 ± 9.01, 27.87 ± 6.10, 13.56 ± 3.30, and 3.05 ± 0.65 mg/dL, respectively. Contents of trace elements such as iron, zinc, copper, and manganese were 40.26 ± 46.21, 98.40 ± 62.47, 24.09 ± 9.03, and 0.90 ± 1.63 µg/dL, respectively. Fat-soluble vitamin concentration was positively correlated with total fat in milk samples, but no significant differences were observed in levels of retinol, α-tocopherol, or minerals based on whether or not lactating women were taking dietary supplements.

CONCLUSIONS

Micronutrient contents of breast milk samples from Korean lactating women were comparable to those of other nations. Retinol and α-tocopherol levels were correlated and also with total fat in breast milk.

The effect of between-breast differences on human milk macronutrients content

OBJECTIVE

Little is known about the effect of maternal handedness and preferential side of breastfeeding upon macronutrients concentration in human milk (HM). We aimed to compare macronutrients content of HM from both breasts, taking into account the self-reported preferential feeding ('dominant') breast, breast size and handedness (right versus left). We tested the null hypothesis that macronutrients content of HM is not affected by breast dominancy, breast size or maternal handedness.

STUDY DESIGN

Fifty-seven lactating mothers were recruited. HM macronutrients were measured after mid manual expression using infrared transmission spectroscopy.

RESULTS

Out of the 57 mothers recruited, 12 were excluded from the analyses because they brought in insufficient samples. Among the 22 who reported a size difference, 16 (73%) had a larger left breast (P<0.001). Approximately a third of women reported no breastfeeding side dominance, a third reported a right dominance and another third reported a left dominance. Breastfeeding side dominance was unaffected by either handedness or breasts size. When size asymmetry was reported (n=22) the dominant side was also the larger breast in 16 (73%) women, the smaller breast in 2 (9%) women, whereas 4 (18%) additional women with asymmetry had no preferential breastfeeding side. There were no statistically significant differences in macronutrients between the right and the left breasts. In multiple stepwise backward regression analysis, fat, carbohydrate, protein and energy contents were unaffected by maternal handedness, breast side dominance or breast size asymmetry.

CONCLUSIONS

Macronutrients content of mid expression HM is unaffected by maternal handedness, breast size or breast side dominance.

Circadian Macronutrients Variations over the First 7 Weeks of Human Milk Feeding of Preterm Infants

BACKGROUND

Little is known about circadian variations of macronutrients content of expressed preterm human milk (HM). This study evaluated diurnal variations of macronutrients and energy content of preterm HM over the first 7 weeks of lactation and tested the hypothesis that values obtained during a morning sample are predictive of those obtained from an evening sample.

MATERIALS AND METHODS

Expressed HM was obtained from 32 mothers of preterm infants (26-33 weeks in gestational age), who routinely expressed all their milk every 3 hours from the beginning of the second to the seventh week after delivery. One aliquot was obtained from the first morning expression and the second from the evening expression. Energy and macronutrients contents were measured using an HM analyzer.

RESULTS

Mean fat and energy contents of all samples obtained during the whole period were significantly higher in evening samples (p < 0.0001). There were no significant differences between morning and evening carbohydrates and protein contents. Concentrations of protein, carbohydrates, and fat from morning samples were predictive of evening concentrations to different extents (R(2) = 0.720, R(2) = 0.663, and R(2) = 0.20, respectively; p < 0.02). The predictability of evening values by morning values was not influenced by the week of lactation at sampling or by individual patients. In repeated-measures analysis of variance performed on 11 patients who completed the whole 7-week period, over time, there was a significant decrease in fat, energy, and protein contents, whereas carbohydrates content remained unchanged. Day-night differences remained significant only for fat content.

CONCLUSIONS

Circadian variations in fat and energy concentrations of HM are consistent over the first 7 weeks of lactation. There are no consistent circadian variations in HM protein and carbohydrates. Over a given day, there are little variations in protein and carbohydrates content, but fat concentrations are more variable, and evening values are less well predicted by morning sample analysis than values for protein or carbohydrates.

Breast milk fat content of mothers to small-for-gestational-age infants

OBJECTIVE

Little is known about the composition of human milk (HM) expressed by mothers of asymmetrically growth-restricted infants. To test the null hypothesis that lactating mothers of small-for-gestational-age (SGA) infants produce milk with fat content similar to that of lactating mothers of infants whose growth is appropriate for gestational age (AGA).

STUDY DESIGN

Fifty-six lactating mothers of newborns (26 SGA and 30 AGA) were recruited within the first 3 days of delivery. Creamatocrit (CMT) levels in HM were measured at 72 h, 7 days and 14 days postdelivery in capillary tubes after centrifugation at 9000 r.p.m. for 5 min.

RESULT

The groups did not differ in terms of maternal age, body mass index, gestational age (GA), pregnancy weight gain and parity. They differed significantly in terms of infant's birth weight by design. The mean CMT levels at the three time points were similar for the two groups. This remained true when timing of the sample (colostrum, transitional, mature milk) was introduced as a confounder in the analysis of variance (general linear model).

CONCLUSION

Fat content of HM is not affected by fetal growth status. We suggest that mothers of SGA infants may be reassured that their milk contains adequate amount of fat that is appropriate for the growth of their infants.

A systematic review and meta-analysis of the nutrient content of preterm and term breast milk

Background

Breast milk nutrient content varies with prematurity and postnatal age. Our aims were to conduct a meta-analysis of preterm and term breast milk nutrient content (energy, protein, lactose, oligosaccharides, fat, calcium, and phosphorus); and to assess the influence of gestational and postnatal age. Additionally we assessed for differences by laboratory methods for: energy (measured vs. calculated estimates) and protein (true protein measurement vs. the total nitrogen estimates).

Methods

Systematic review results were summarized graphically to illustrate the changes in composition over time for term and preterm milk. Since breast milk fat content varies within feeds and diurnally, to obtain accurate estimates we limited the meta-analyses for fat and energy to 24-hour breast milk collections.

Results

Forty-one studies met the inclusion criteria: 26 (843 mothers) preterm studies and 30 (2299 mothers) term studies of breast milk composition. Preterm milk was higher in true protein than term milk, with differences up to 35% (0.7 g/dL) in colostrum, however, after postnatal day 3, most of the differences in true protein between preterm and term milk were within 0.2 g/dL, and the week 10–12 estimates suggested that term milk may be the same as preterm milk by that age. Colostrum was higher than mature milk for protein, and lower than mature milk for energy, fat and lactose for both preterm and term milk. Breast milk composition was relatively stable between 2 and 12 weeks. With milk maturation, there was a narrowing of the protein variance. Energy estimates differed whether measured or calculated, from −9 to 13%; true protein measurement vs. the total nitrogen estimates differed by 1 to 37%.

Conclusions

Although breast milk is highly variable between individuals, postnatal age and gestational stage (preterm versus term) were found to be important predictors of breast milk content. Energy content of breast milk calculated from the macronutrients provides poor estimates of measured energy, and protein estimated from the nitrogen over-estimates the protein milk content. When breast milk energy, macronutrient and mineral content cannot be directly measured the average values from these meta-analyses may provide useful estimates of mother’s milk energy and nutrient content.

Soft plastic bag instead of hard plastic container for long-term storage of breast milk

OBJECTIVE

To compare the fat content and contamination of expressed breast milk (EBM) before and after storage (30 d) in hard polypropylene containers (HC) and soft polyethylene bags (SB) containers.

METHODS

Ninety specimens of EBM were collected into HC and separated into two HC and two SB. The fat content of each specimen of EBM in HC and SB was measured and cultures were performed. The specimens in the second HC and SB containers were kept frozen for 30 d before thawing and then measuring the fat content and performing cultures.

RESULTS

The means ± SD of the fat content of fresh and thawed EBM in HC were 2.98 ± 0.97 and 2.66 ± 0.88 g/100 ml, respectively, with a loss of 0.32 g/100 ml (p < 0.001). The means ± SD of the fat content of fresh and thawed EBM in SB were 3.06 ± 1.00 and 2.77 ± 0.91 g/100 ml, respectively, with a mean loss of 0.29 g/100 ml during storage (p < 0.001). The loss of fat content during frozen storage did not differ significantly between the two types of containers (p = 0.53). All bacterial cultures of fresh and thawed EBM in HC and SB showed only nonpathogenic organisms.

CONCLUSIONS

SB can replace HC for the long-term storage of frozen EBM of up to 30 d without deleterious effects on fat loss or contamination.

Pooling expressed breastmilk to provide a consistent feeding composition for premature infants

OBJECTIVE

We hypothesized that pooling a mother's expressed breastmilk for 24 hours compared with individual pump session collection of milk would provide a more consistent caloric product without increasing bacterial contamination.

STUDY DESIGN

We investigated 24-hour pooled breastmilk collection by enrolling 19 mothers who were expressing milk for their infants. Mothers followed a standardized milk collection protocol for 4 study days: daily milk was pooled in a sterile 1-L bottle on Day 1, and on Day 2 milk was aliquoted for each pump session into a sterile 120-mL container. The next week the order of collection was reversed. Milk samples were plated, incubated, and evaluated for bacteria colonization. Milk samples were analyzed for protein, fat, and carbohydrate content.

RESULTS

There was inherently less variability in the caloric and nutrient content of pooled milk compared with individual samples, in which caloric density varied by as much as 29%. Mother's milk had highly variable bacterial counts ranging from 0 to greater than 100,000 colonies/mL. High bacteria counts (>100,000 colonies/mL) occurred in 14.7% (31 of 211) of individual samples compared with 8.6% (three of 35) of pooled samples (p=0.39).

CONCLUSIONS

Twenty-four-hour pooling of human milk reduces nutrient and caloric variability without increasing bacterial counts.

The effect of advanced maternal age upon human milk fat content

BACKGROUND

Little is known about the effect of maternal age on human milk (HM) composition. This study was designed to study fat content, estimated by creamatocrit (CMT), in HM collected in the first 2 weeks of life in older (≥ 35 years) compared with younger (<35 years) mothers.

STUDY DESIGN AND METHODS

Ninety lactating mothers (48 older, 42 younger) of newborns were recruited within the first 3 days of delivery. CMTs were measured at 72 hours, 7 days, and 14 days after delivery for HM in a capillary tube after centrifugation at 5,366 g for 5 minutes.

RESULTS

The groups did not differ in terms of maternal height and diet, infant birth weight, gestational age (GA), or pregnancy weight gain. They differed significantly in terms of maternal age and parity. Mean colostrum CMT was significantly higher in the group of older mothers. Colostrum CMT correlated positively with maternal age (R(2)=0.11, p=0.006) and inversely with GA (R(2)=0.1, p=0.03) but did not relate with either maternal weight or body mass index. CMT at age 7 days and 2 weeks was not affected by maternal age or GA. In multivariate regression analysis colostrum CMT correlated significantly only with maternal age and GA (R(2)=0.3, p<0.001).

CONCLUSIONS

Colostrum fat content of older mothers is much higher than that of younger mothers and inversely related with GA at delivery. This increase in colostrum fat content obtained from mothers with advanced age may be due to increased fat synthesis and excretion in milk, reduced water content of milk, or a combination of both.

Does the circadian system regulate lactation?

Environmental variables such as photoperiod, heat, stress, nutrition and other external factors have profound effects on quality and quantity of a dairy cow's milk. The way in which the environment interacts with genotype to impact milk production is unknown; however, evidence from our laboratory suggests that circadian clocks play a role. Daily and seasonal endocrine rhythms are coordinated in mammals by the master circadian clock in the hypothalamus. Peripheral clocks are distributed in every organ and coordinated by signals from the master clock. We and others have shown that there is a circadian clock in the mammary gland. Approximately 7% of the genes expressed during lactation had circadian patterns including core clock and metabolic genes. Amplitude changes occurred in the core mammary clock genes during the transition from pregnancy to lactation and were coordinated with changes in molecular clocks among multiple tissues. In vitro studies using a bovine mammary cell line showed that external stimulation synchronized mammary clocks, and expression of the core clock gene, BMAL1, was induced by lactogens. Female clock/clock mutant mice, which have disrupted circadian rhythms, have impaired mammary development and their offspring failed to thrive suggesting that the dam's milk production was not adequate enough to nourish their young. We envision that, in mammals, during the transition from pregnancy to lactation the master clock is modified by environmental and physiological cues that it receives, including photoperiod length. In turn, the master clock coordinates changes in endocrine milieu that signals peripheral tissues. In dairy cows, it is clear that changes in photoperiod during the dry period and/or during lactation influences milk production. We believe that the photoperiod effect on milk production is mediated, in part by the 'setting' of the master clock with light, which modifies peripheral circadian clocks including the mammary core clock and subsequently impacts milk yield and may impact milk composition.

The creamatocrit, fat and energy concentration in human milk produced by mothers of preterm and term infants

OBJECTIVE

The objective of this study was to investigate the composition of breast milk which had been gathered from mothers for over first 2 weeks of lactation and to compare the changes in composition of preterm and term milk.

METHODS

A prospective, single center study was provided in Warsaw, Poland. The samples of breast milk from 22 mothers who had delivered prematurely and 39 mothers who had given birth to term infants were collected. The creamatocrit, energy and fat concentration were estimated in each participant's breast milk sample twice a day (morning and night hours).

RESULTS

The lowest creamatocrit, calories and fat concentration was indicated in the preterm milk obtained in the morning (4.86%, 663.8 kcal/L and 33.6 g/L, respectively). The highest milk parameters were observed in the night samples of full-term milk and measured (9.6%, 919.7 kcal/L, and 60.7 g/L, respectively). No significant differences in analysed parameters were observed between preterm and full-term milk (p>0.05). In summary, creamatocrit, calories and lipid concentration in breast milk shows the daily differences. Colostrum and mature milk from mothers of preterm neonates differed from colostum and mature milk from mothers of term neonates. They had lipid contents, creamatocrit level and calorific value.

Centralized Model of Human Milk Preparation and Storage in a State-of-the-Art Human Milk Lab

Strategies to ensure safe handling and administration of human milk for sick, hospitalized infants are necessary to avoid compromising the integrity of the milk and to prevent administration to the wrong patient. A centralized system of storing and preparing human milk in a milk lab that incorporates multiple verification points using a bar-coding system ensures that the right milk is prepared, delivered, and administered to the right patient, at the right time, and with the right additives. A team of skilled technicians dedicated to handling and preparing human milk, and a system of careful temperature control of refrigerators, freezers, water baths, and warmers, ensures the safety and quality of the milk. Nurses spend less time away from the bedside and more time in patient care when the milk is stored and prepared in a milk lab and delivered ready-to-feed to the bedside. Patient and staff satisfaction are high when a centralized system of storing and preparing human milk is implemented in the hospital setting.

Efficacy of creamatocrit technique in evaluation of premature infants fed with breast milk

BACKGROUND

Most premature babies are discharged with low body weight. Creamatocrit represents the lipid concentration of breast milk. We expected the creamatocrit technique could be applied in the nutrition plan for premature infants who were exclusively fed by human milk.

METHODS

Breast milk samples were obtained from the mothers whose babies were admitted to the neonatal intensive care unit or sick baby room. The breast milk provider was enrolled under the criteria of stable breast milk expression 2 weeks after having given birth. Breast milk was collected for 7 consequent days. Creamatocrit technique and calorie analysis were performed on the processed breast milk samples.

RESULTS

Fourteen pairs of mothers and infants were enrolled in our study. The median gestational age and birth weight were 29 weeks (27-36 weeks) and 1,393 g (680-3050 g), respectively. The mean calorie and creamatocrit values for all the 98 breast milk samples were 0.67 kcal/mL and 5.98%, respectively. The linear correlation between creamatocrit value and laboratory-measured calories was found to be calories (kcal/mL)=0.39+0.048×creamatocrit (%) (p<0.05).

CONCLUSION

We established the relation equation of creamatocrit and calories for the first time in Chinese population, which is convenient and accurate for evaluating calories provided for premature infants fed with breast milk.

Homeorhetic adaptation to lactation: comparative transcriptome analysis of mammary, liver, and adipose tissue during the transition from pregnancy to lactation in rats

Tissue-specific shifts in a dam's metabolism to support fetal and neonatal growth during pregnancy and lactation are controlled by differential expression of regulatory genes. The goal of this study was to identify a more detailed cohort of genes in mammary, liver, and adipose tissue that are transcriptionally controlled during the pregnancy to lactation evolution and explore the relationship of these genes to core clock genes. Total RNA was isolated from mammary, liver and adipose tissues collected from rat dams on day 20 of pregnancy (P20) and day 1 of lactation (L1) and gene expression was measured using Rat 230 2.0 Affymetrix GeneChips. Gene functional analysis revealed that pathway associated metabolism (carbohydrate, amino acid, lipid, cholesterol, protein) were enriched (P < 0.001) in the mammary gland during P20 to L1 transition. Approximately 50% of the genes associated with solute transport, as well as lipogenesis were up-regulated in the mammary gland during P20 to L1 transition compared to 10% in liver and 15% in adipose tissue. Genes engaged in conveying glucose (INSR, GLUT1, GLUT4, SGLT1, and SGLT2), bicarbonate (SLC4), sodium (SLC9), zinc (SLC30), copper (SLC31), iron (SLC40) in tandem with rate-limiting lipogenic genes (ACACA, FASN, PRLR, SREBP2, THRSP) were specifically enriched in the mammary gland during the P20 to L1 evolution. Our results provide insight into a cross-tissue transcriptional repertoire that is associated with homeorhetic adaptation needed to support lactation, and at the onset of lactation the mammary gland becomes a factory for macromolecular biosynthesis through inducing genes participating in nutrient transfer and lipid biosynthesis.

Consistent circadian variations in creamatocrit over the first 7 weeks of lactation: a longitudinal study

OBJECTIVE

The objective of this study was to test the hypothesis that fat content of expressed human milk from mothers of preterm infants is higher in samples expressed in the evening than in the morning during the first 7 weeks of lactation.

METHODS

The authors collected samples of expressed human milk obtained from 22 mothers of growing preterm infants, born at 26 to 31 weeks gestation, who routinely expressed all their milk every 3 hours using breast pump from the beginning of the second week to the seventh week after delivery. One aliquot was obtained from the first morning expression and the second from the evening expression. The entire aliquot was collected and mixed, and creamatocrit (CMT) was measured in a capillary. Results are expressed as mean +/- standard deviation (SD), and analyses were by repeated measures analysis of variance.

RESULTS

Mean CMT was significantly higher in evening than morning samples during the whole lactation period, week after week (p < 0.0001). Neither CMT values nor the morning-evening difference in CMT values correlated with gestational age, birth weight, or week of lactation. Morning CMT correlated significantly with evening CMT (R(2) = 0.28, p < 0.0001).

CONCLUSIONS

Circadian variations in CMT are consistent during the first 7 weeks of lactation. The authors speculate that if higher caloric content expressed human milk is needed in a specific preterm infant, evening samples should be used preferentially, if available.