Human milk total lipid and cholesterol are dependent on interval of sampling during 24 hours

Daily and within-feed variation of macro- and trace-element concentrations in human milk and implications for sampling

BACKGROUND

Daily variations of macro- and trace-elements in human milk (HM) are not well characterised and sampling protocols are highly variable between studies.

OBJECTIVES

To investigate diurnal and within-feed variation of HM macro- and trace-elements using pre- and post- feed concentrations and to compare infant intake estimates using limited samples with measured 24-hour intake.

METHODS

HM Samples were collected pre- and post- every feed in a 24-hour period from 11 mother-infant dyads. Test-weighing was used to determine the volume of HM consumed in each feed. For macro- and trace-elements within-feed and daily variation was measured. Intake estimated from a morning pre-feed sample was compared to the measured milk intake calculated from every feed over 24-hours. Macro- and trace-elements concentrations were measured using ICP-MS. Linear mixed modelling was used for statistical analysis.

RESULTS

Average intake of HM was 737 ± 63 mL for infants aged 1-6 months and 508 ± 50 for infants aged 6-12 months. Pre- and post-feed HM variation was found for phosphorus, calcium, manganese, iron, copper, zinc, selenium, molybdenum, and iodine (p < 0.05). Variation across 24 h was found for magnesium, phosphorus, potassium, manganese, iron, and selenium (p < 0.05). Estimated intake using morning, pre-feed samples resulted in significantly lower intake when compared to measured milk intake for iron, phosphorus, selenium, and manganese (p < 0.05).

CONCLUSION

Standardised sampling protocols using large sample volumes and multiple collections over 24-hours provide a calculated intake that is more reflective of actual infant HM macro- and trace-elements intake.

Variability of Lipids in Human Milk

Lipids in breastmilk play a critical role in infant growth and development. However, few studies have investigated sources of variability of both high- and low-abundant milk lipids. The objective of our study was to investigate individual and morning-evening differences in the human milk lipidome. In this study, a modified two-phase method (MTBE: Methanol 7:2) was validated for the extraction of lipids from human breastmilk. This method was then applied to samples from a group of 20 healthy women to measure inter- and intra-individual (morning versus evening) variability of the breastmilk lipidome. We report here the levels of 237 lipid species from 13 sub-classes using reversed-phase liquid chromatography mass spectrometry (RP-LCMS) and direct-infusion mass spectrometry (DI-MS). About 85% of lipid species showed stable inter-individual differences across time points. Half of lipid species showed higher concentrations in the evening compared with the morning, with phosphatidylethanolamines (PEs) and triacylglycerols (TAGs) exhibiting the largest changes. In morning and evening samples, the biological variation was greater for diacylglycerols (DAGs) and TAGs compared with phospholipids and sphingolipids, and the variation in DAGs and TAGs was greater in evening samples compared with morning samples. These results demonstrate that variation in the milk lipidome is strongly influenced by individual differences and time of day.

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.

Human Milk Short-Chain Fatty Acid Composition is Associated with Adiposity Outcomes in Infants

BACKGROUND

Presumed benefits of human milk (HM) in avoiding rapid infancy weight gain and later obesity could relate to its nutrient composition. However, data on breast milk composition and its relation with growth are sparse.

OBJECTIVE

We investigated whether short-chain fatty acids (SCFAs), known to be present in HM and linked to energy metabolism, are associated with infancy anthropometrics.

METHODS

In a prospective birth cohort, HM hindmilk samples were collected from 619 lactating mothers at 4-8 wk postnatally [median (IQR) age: 33.9 (31.3-36.5) y, body mass index (BMI) (kg/m2): 22.8 (20.9-25.2)]. Their offspring, born at 40.1 (39.1-41.0) wk gestation with weight 3.56 (3.22-3.87) kg and 51% male, were assessed with measurement of weight, length, and skinfold thickness at ages 3, 12, and 24 mo, and transformed to age- and sex-adjusted z scores. HM SCFAs were measured by 1H-nuclear magnetic resonance spectroscopy (NMR) and GC-MS. Multivariable linear regression models were conducted to analyze the relations between NMR HM SCFAs and infancy growth parameters with adjustment for potential confounders.

RESULTS

NMR peaks for HM butyrate, acetate, and formic acid, but not propionate, were detected. Butyrate peaks were 17.8% higher in HM from exclusively breastfeeding mothers than mixed-feeding mothers (P = 0.003). HM butyrate peak values were negatively associated with changes in infant weight (standardized B  = -0.10, P = 0.019) and BMI (B = -0.10, P = 0.018) between 3 and 12 mo, and negatively associated with BMI (B = -0.10, P = 0.018) and mean skinfold thickness (B = -0.10, P = 0.049) at age 12 mo. HM formic acid peak values showed a consistent negative association with infant BMI at all time points (B < = -0.10, P < = 0.014), whereas HM acetate was negatively associated with skinfold thickness at 3 mo (B = -0.10, P = 0.028) and 24 mo (B = -0.10, P = 0.036).

CONCLUSIONS

These results suggest that HM SCFAs play a beneficial role in weight gain and adiposity during infancy. Further knowledge of HM SCFA function may inform future strategies to support healthy growth.

Sterols in human milk during lactation: bioaccessibility and estimated intakes

Total sterol content decreased to the half throughout lactation, being their intake lower at colostrum and its bioaccessibility higher at first month.

Sterol Composition in Infant Formulas and Estimated Intake

Sterol contents in infant formulas (IFs) from the European market were determined, and their intakes by infants between 0 and 6 months were evaluated. Total animal sterols (mg/100 mL) ranged from 1.71 to 5.46, cholesterol being the main animal sterol (1.46-5.1). In general, cholesterol and desmosterol were lower than the human milk (HM) values indicated by other authors. Total plant sterol (mg/100 mL) ranged from 3.1 to 5.0. β-Sitosterol, the most abundant phytosterol, ranged from 1.82 to 3.01, followed by campesterol (0.72-1.15), stigmasterol (0.27-0.53), and brassicasterol (0.14-0.28). Cholesterol intake (mg/day) ranged from 9 to 51 and plant sterol intake (mg/day) from 19 to 50. The sterol profile of IFs is highly dependent on the type and quantity of fats used in their formula. The use of bovine milk fat and milk fat globule membrane in the IFs can approximate the profile of animal sterols to those found in HM, though cholesterol intakes in breastfed infants are still higher than in formula-fed infants.

Relationship of insulin, glucose, leptin, IL-6 and TNF-α in human breast milk with infant growth and body composition

BACKGROUND

Numerous appetite, growth, obesity-related hormones and inflammatory factors are found in human breast-milk, but there is little evidence on their relationship with infant body composition. OBJECTVIE: The purpose of the present cross-sectional pilot study was to assess the cross-sectional associations of appetite-regulating hormones and growth factors (leptin, insulin and glucose) and inflammatory factors (interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α)) in human breast-milk with infant size, adiposity, and lean tissue at 1-month of age in healthy term infants.

METHODS

Human breast-milk was collected from nineteen exclusively breast-feeding mothers using one full breast expression between 8:00 and 10:00 a.m. The milk was then mixed, aliquoted, stored at -80°C and then centrifuged to remove the milk fat, prior to analyses using commercially available immunoassay kits; milk analytes were natural log transformed prior to analysis. Infant body composition was assessed using a Lunar iDXA v11-30.062 scanner (Infant whole body analysis enCore 2007 software, GE, Fairfield, CT).

RESULTS

Maternal pre-pregnancy BMI was positively associated with milk leptin concentration (P = 0.0027), and so maternal-BMI-adjusted Spearman correlations were examined between breast-milk analytes and infant growth and body composition variables. As previously reported, greater milk leptin was associated with lower BMIZ (BMI-for-age z-score based on WHO 2006 growth charts; r = -0.54, P = 0.03). Glucose was positively associated with relative weight (r = 0.6, P = 0.01), and both fat and lean mass (0.43-0.44, P < 0.10). Higher concentrations of milk insulin were associated with lower infant weight, relative weight, and lean mass (r = -0.49-0.58, P < 0.06). Higher milk IL-6 was associated with lower relative weight, weight gain, percent fat, and fat mass (r = -0.55-0.70, P < 0.03 for all), while higher TNF-α was associated with lower lean mass (r = -0.58, P = 0.05), but not measures of adiposity.

CONCLUSIONS

These preliminary data suggest for the first time that in the first months of life, breast-milk concentrations of insulin, glucose, IL-6 and TNF-α, in addition to leptin, may be bioactive and differentially influence the accrual of fat and lean body mass.

Lipids in human milk

I have reviewed recent (March 1995-December 1997) papers on human milk lipids including many on fatty acid (FA) composition. The effects of maternal diets on the profiles are apparent. However, more data on the composition of milk lipids are needed. It is noteworthy that so few papers on milk FA composition have reported analyses using high-resolution gas-liquid chromatography columns. Two of these were on milk from women in North America. The diets in North America are varied and the number of analyses few. We do not have a reliable data base showing the ranges of biologically important acids. Except for the gangliosides, few new data on the other lipids appeared during this period.

The lipids in human milk

The summary will be limited to the areas that should be intensively investigated. The first is: determination of fatty acid profiles using modern methods on a world wide basis. We have no more than five or six papers in which my criterion was applied, one from Canada and the remainder from Europe with some data from Africa. Obviously, milk cannot be used as the gold standard on this meager data base. The second area is analysis of TG structure. These analyses are difficult, but structure is one of the factors controlling digestion. Data on the effects of maternal diet on structure would be useful. The third area is the role of primary or derived milk lipids as microbicidal agents. The fourth area is examination of globule parameters, i.e. number, size, volume, surface, and how they are affected by diet. There are many others which may interest the reader.