Protein Concentrations In Human Milk Research Articles

The Impact of Maternal Obesity on Human Milk Macronutrient Composition: A Systematic Review and Meta-Analysis

ObjectivesThis article aimed to provide a synthesis of studies evaluating the effects of maternal overweight and obesity, including body mass index (BMI) and other measures of adiposity, on the concentrations of macronutrients (fat, protein and lactose) in human milk (HM). MethodsEMBASE, MEDLINE/PubMed, Cochrane Library, Scopus, Web of Science and ProQuest databases were searched for relevant articles. Two authors conducted screening, data extraction and quality assessment independently. Meta-analyses of eligible studies were conducted using Review Manager software version 5.3. ResultsA total of 31 studies (5078 lactating women) were included in the qualitative synthesis and 9 studies (872 lactating women) in the quantitative synthesis. The meta-analysis indicated that maternal overweight and obesity were associated with higher concentrations of fat in mature HM (p = 0.01) and lactose in colostrum (p = 0.002). While the qualitative analyses broadly supported the findings of the meta-analysis, the qualitative assessment identified considerable variability in the results between studies and low quality of many of the included studies, making it difficult to draw robust conclusions. ConclusionsOverall, maternal BMI and adiposity measurements were associated with differences in the concentrations of fat and lactose in HM, however the direction of change was dependent on the stage of lactation, whereas protein concentration in HM did not appear to differ between overweight and/or obese and normal weight women. This is particularly relevant considering potential implications of higher HM fat concentration on both growth and fat deposition during the first few months of infancy and long-term risk of obesity. Funding SourcesGEL was supported by a FOODplus Early Life Nutrition Scholarship, The University of Adelaide. BSM received a Career Development Award from the National Health and Medical Research Council of Australia (NHMRC).

Daily variation of macronutrient concentrations in mature human milk over 3 weeks

Human milk (HM) composition is known to be highly variable, both between individuals and across the duration of lactation. It is less clear, however, to what extent fat, lactose and protein concentrations in HM change daily over shorter time periods in mature HM, and no studies have evaluated this to date. The aim of this study was to systematically assess and compare HM macronutrient concentrations in samples collected at different times of day, from left and right breasts and daily across a 3-week period in the same woman. Fifteen lactating women (1.6–4.9 months postpartum) collected daily pre-feed HM samples from both breasts each morning for 21 consecutive days and completed intensive sampling once a week (morning, afternoon and evening samples) during this period. Concentrations of fat, protein and lactose in HM did not differ according to time of day, day of week or breast used for collection. The results of this study suggest that pre-feed samples collected at any point across a 3-week period and from either the left or right breast provide comparable measures of fat, protein and lactose concentrations in mature HM, in pragmatic studies where women are collecting their own HM samples.Clinical trial registration: Australian New Zealand Clinical Trials Registry (ACTRN12619000606189).

The Impact of Maternal Obesity on Human Milk Macronutrient Composition: A Systematic Review and Meta-Analysis

Maternal obesity has been associated with changes in the macronutrient concentration of human milk (HM), which have the potential to promote weight gain and increase the long-term risk of obesity in the infant. This article aimed to provide a synthesis of studies evaluating the effects of maternal overweight and obesity on the concentrations of macronutrients in HM. EMBASE, MEDLINE/PubMed, Cochrane Library, Scopus, Web of Science, and ProQuest databases were searched for relevant articles. Two authors conducted screening, data extraction, and quality assessment independently. A total of 31 studies (5078 lactating women) were included in the qualitative synthesis and nine studies (872 lactating women) in the quantitative synthesis. Overall, maternal body mass index (BMI) and adiposity measurements were associated with higher HM fat and lactose concentrations at different stages of lactation, whereas protein concentration in HM did not appear to differ between overweight and/or obese and normal weight women. However, given the considerable variability in the results between studies and low quality of many of the included studies, further research is needed to establish the impact of maternal overweight and obesity on HM composition. This is particularly relevant considering potential implications of higher HM fat concentration on both growth and fat deposition during the first few months of infancy and long-term risk of obesity.

Individualized Human Milk Fortification to Improve the Growth of Hospitalized Preterm Infants

Human milk (HM) is the first choice for preterm infants, but exclusive HM feeding is inadequate for the growth of very preterm infants. The hypothesis of this trial is that infants fed according to an individualized fortification regimen will have higher protein intake and improved weight gain velocity (WGV). A prospective, randomized, controlled study was conducted. Infants <34 weeks of gestational age were enrolled when enteral feeding volume reached 60 mL/kg/d and were randomly allocated to the individualized fortification (IF) group or the standard fortification group. The IF group was fed using a regimen that featured modifying HM fortifier and supplemental protein powder based on the protein concentration in HM, current body weight of infants, and blood urea nitrogen (fortification level was set as L-1, L0, L1, L2, L3; the amount of HM fortifier and protein powder were determined accordingly). Between September 2012 and August 2016, 51 preterm infants completed the study. In the IF group, 62.5% (15/24) of preterm infants were fed with HM fortified to level 1, 29.2% (7/24) to level 2, and 12.5% (3/24) to level 3. The WGV of the third week in the IF group was greater than the standard group (20.8 ± 7.9 vs 14.9 ± 4.5 g/kg/d, P = 0.022). About two-thirds of preterm infants needed to adjust the HM fortification to a higher level. The WGV of infants in the IF group was better than that of the standard group in the third week of this study.

A Longitudinal Quantification of Total Protein in Human Milk From Three Global Cohorts: a GEHM Study

The quantity of protein in human milk is believed to be important for growth and development of breastfed infants. This study, in support of the Global Exploration of Human Milk (GEHM) collaboration, reports total protein concentration as a weight to weight percentage based on Dumas combustion in longitudinal samples collected from three global cohorts (Mexico, China, and USA) at 4, 13, 26, and 52 weeks lactation. Average total protein decreased rapidly from 4 to 13 weeks of lactation (1.40 ± 0.14% to 1.16 ± 0.16%) and then remained relatively stable to 52 weeks (1.17 ± 0.13%). Similar trends have been reported and are further strengthened by data generated from these samples collected using standardized techniques. Since some components of human milk, including protein, are known to vary diurnally, samples for the GEHM study were collected in the morning by emptying an entire breast via electric pump. Additionally, commercially available human milk standards (HMS) and NIST Standard Reference Material (SRM) 1849a were incorporated into analyses to further verify the accuracy of Dumas combustion for determination of total protein in human milk. The HMS analyzed by combustion all fell within protein certified ranges determined by Kjeldahl methodology. SRM was analyzed before, during, and after each analytical run as a check sample. These added assessments of accuracy, as well as the integration of samples from different geographical populations across multiple points of lactation, strengthen the foundation of knowledge into total protein concentration in human milk. This research was supported by Mead Johnson Pediatric Nutrition Institute.

Variations in the concentration of total human milk proteins in the first month of lactation

Human milk proteins are maximally adapted to physiological needs of a neonate. Thus, depending on the speed of the neonatal growth and development, the content of milk proteins changes, both in quantity and quality. The study was conducted in order to determine variations of total protein concentrations in milk in the first and third lactation week in lactating mothers of term and preterm neonates. Also, we analyzed the influence of the mode of delivery, neonatal Apgar score and parity on the concentration of human milk proteins in both lactation phases. The study aims were evaluated on the sample of 48 women, of whom 33 were mothers of term neonates and 15 of neonates born between the 34th to 37th gestational weeks. Total protein level of the lactation milk from the middle phase was determined using the standard laboratory method (Lowry et al., 1951), and the obtained differences were analyzed by t-test. Total protein concentration in term colostrum was 17.60-45.17 g/l (X = 24.71 +/- 5.19), while in preterm colostrum it was 28.39-73.30 g/l (X = 39.17 +/- 11.08). The total protein level of mature milk in women who had term delivery was 11.90-22.11 g/l (X = 16.39 +/- 2.96), while in women who had preterm delivery it was 14.50-44.19 g/l (X = 23.25 +/-8.96). The obtained results indicated that total protein concentration in women who had preterm delivery was significantly higher than that of women who had term delivery, both in the colostral and mature phase of lactation. (p < 0.01). Also, the difference in the protein concentration was statistically highly significant (p < 0.01) in the colostral and mature phase of lactation, both in women who had term and preterm delivery. Variations in the total protein level of human milk were not significant, depending on the prematurity stage, the mode and severity of delivery and parity, both in the first and third week of lactation. Our results show that total protein concentration in human milk was significantly higher in the first than the third week of lactation. In both lactation phases, milk protein content was higher in women who had preterm delivery than those having had term delivery. The influence of prematurity stage, the mode and severity of delivery and parity on the total milk protein level was not significant.

Cobalamin and cobalamin-binding capacity in human milk

Information on variability of cobalamin and its binding protein concentrations in human milk is scarce. We investigated their relationship and longitudinal changes up to the third month of lactation, and their inter and intraindividual variability within the day, between breasts and within the feed in samples from nine healthy lactating women. Cobalamin and its binding protein, cobalophin, expressed as cobalamin-binding capacity, presented higher correlations in colostrum and transition milk (r=0.621 and 0.842, respectively) than in other periods of lactation (r<0.500). Cobalamin was significantly higher (p<0.01) in colostrum (mean, all subjects: 0.35 nmol/l) than in the third month of lactation (0.25 nmol/l), whereas cobalamin-binding capacity was significantly lower (p<0.01) in colostrum (29 nmol/l) than in the third month (43 nmol/l). However, the patterns of individual longitudinal variation were different among women. There was a high intraindividual diurnal variability, with coefficients of variation (CV) in different individuals ranging from 15 to 42% for cobalamin, and from 16 to 52% for the binding protein, reflecting the variations between breasts and between different moments of collection within a day. Interindividual CV for samples obtained under identical conditions ranged from 32% (colostrum, morning, left breast) to 85% (1st month, afternoon, right breast) for cobalamin, and from 20% (2nd month, morning, right breast) to 90% (1st month, evening, right breast) for cobalamin-binding capacity. Comparing the means of all subjects in each period of lactation there were no significant differences, or even trends, in cobalamin and its binding protein between breasts, fore and hindmilk, and morning, afternoon and evening samples. Therefore, a representative sample of breast milk for cobalamin analysis in population studies can be obtained within a day of a determined lactation period irrespective of the time of day, breast or moment within a feed.

Sequential changes in the antimicrobial protein concentrations in human milk during lactation and its relevance to banked human milk.

The concentrations of eight antimicrobial proteins, 11S IgA, IgG, IgM, alpha 1-antitrypsin, lactoferrin, lysozyme, C3, and C4 were measured in sequential samples of colostrum, transitional and mature milk from 47 women in Merseyside, England by single radial immunodiffusion. Concentrations were highest in colostrum and then declined until relatively stable concentrations were reached in mature milk. A wide variation in protein concentrations was noted in the milk from different individuals at any given postpartum time interval and this was particularly so during the first 4 days postpartum. The decline in individual antimicrobial protein concentrations seen in samples of transitional milk appeared to take a variable period of time to stabilize to mature milk concentrations of each protein. These variations may reflect different rates of transport or secretion of these proteins from the alveolar epithelial cells into the alveolar lumen. Because of the wide variations in antimicrobial proteins observed in milk samples from the individuals in this study at similar postpartum time intervals, it is suggested that banked milk should be monitored not only for bacterial contamination, but also for levels of antimicrobial proteins, if it is considered that a major advantage of unprocessed human milk is the immune protection which it confers.