Impact of breastfeeding and other early-life factors on the development of the oral microbiome.

The oral cavity is home to the second most diverse microbiome in the human body. This community contributes to both oral and systemic health. Acquisition and development of the oral microbiome is a dynamic process that occurs over early life; however, data regarding longitudinal assembly of the infant oral microbiome is scarce. While numerous factors have been associated with the composition of the infant oral microbiome, early feeding practices (breastfeeding and the introduction of solids) appear to be the strongest determinants of the infant oral microbiome. In the present review, we draw together data on the maternal, infant, and environmental factors linked to the composition of the infant oral microbiome, with a focus on early nutrition. Given evidence that breastfeeding powerfully shapes the infant oral microbiome, the review explores potential mechanisms through which human milk components, including microbes, metabolites, oligosaccharides, and antimicrobial proteins, may interact with and shape the infant oral microbiome. Infancy is a unique period for the oral microbiome. By enhancing our understanding of oral microbiome assembly in early life, we may better support both oral and systemic health throughout the lifespan.

Is Secretory Activation Delayed in Women with Type Two Diabetes? A Pilot Study.

(1) Background: Breastfeeding duration may be reduced in women with type 2 diabetes. Delayed secretory activation (SA) is associated with poorer breastfeeding outcomes; however, no prior studies have examined SA in women with type 2 diabetes. This pilot study aimed to assess SA in women with type 2 diabetes by assessing breastmilk constituents. Secondary aims were to assess breastfeeding rates postpartum, and contributory factors. (2) Methods: A prospective cohort of pregnant women with type 2 diabetes (n = 18) and two control groups with age- and parity-matched nondiabetic pregnant women (body mass index (BMI)) matched (n = 18) or normal-range BMI (n = 18)) were recruited. Breastmilk constituents (citrate, lactose, protein, and fat) were measured twice daily for 5 days postpartum and compared between groups. Associations between peripartum variables, breastmilk constituents, and breastfeeding at 4 months postpartum were explored. (3) Results: Women with type 2 diabetes had a slower increase in breastmilk citrate concentration postpartum, indicative of delayed SA, compared to both control groups. Higher predelivery insulin doses in women with type 2 diabetes were associated with increasing time to SA. Both women with type 2 diabetes and BMI-matched controls were less likely to fully breastfeed at 4 months, compared with normal-BMI controls. (4) Conclusion: SA is delayed in women with type 2 diabetes when compared to BMI-matched and normal-BMI women. Women with type 2 diabetes are less likely to fully breastfeed, at hospital discharge and by 4 months postpartum, compared to women with normal-BMI.

Human Milk Oligosaccharides and Bacterial Profile Modulate Infant Body Composition during Exclusive Breastfeeding.

Human milk is a complex and variable ecosystem fundamental to the development of newborns. This study aimed to investigate relationships between human milk oligosaccharides (HMO) and human milk bacterial profiles and infant body composition. Human milk samples (n = 60) were collected at two months postpartum. Infant and maternal body composition was measured with bioimpedance spectroscopy. Human milk bacterial profiles were assessed using full-length 16S rRNA gene sequencing and 19 HMOs were quantitated using high-performance liquid chromatography. Relative abundance of human milk bacterial taxa were significantly associated with concentrations of several fucosylated and sialylated HMOs. Individual human milk bacteria and HMO intakes and concentrations were also significantly associated with infant anthropometry, fat-free mass, and adiposity. Furthermore, when data were stratified based on maternal secretor status, some of these relationships differed significantly among infants born to secretor vs non-secretor mothers. In conclusion, in this pilot study the human milk bacterial profile and HMO intakes and concentrations were significantly associated with infant body composition, with associations modified by secretor status. Future research designed to increase the understanding of the mechanisms by which HMO and human milk bacteria modulate infant body composition should include intakes in addition to concentrations.

Macro- and Trace-Element Intake from Human Milk in Australian Infants: Inadequacy with Respect to National Recommendations.

Longitudinal variations of macro- and trace elements in human milk (HM) are not well characterised, and therefore, the recommendations for intake for Australian infants require more evidence to ensure accuracy. We aimed to investigate the longitudinal variation of HM macro- and trace-element concentrations (1-12 months) and infant intake (1-6 months) and to investigate the relationships between intake and infant growth parameters at 3 and 6 months, and determine if intake was sufficient when compared to national guidelines. HM samples were collected monthly for the first 6 months and then at 9 and 12 months postpartum from mother-infant dyads (n = 83). Test-weighing was used to determine the volume of HM consumed daily. Element concentrations (Na, Ca, K, Mg, P, I, Se, Zn, Cu, Mn, Mo, and Fe) were measured using ICP-MS, and intake was calculated using the measured concentrations and the volume of HM consumed. The average intake of HM was 776.3 ± 24.0 mL for the infants. Changes in concentration from months 1 to 12 postpartum were observed for all the measured micronutrients (all p < 0.05). The calculated intakes of all the macro- and trace elements showed that 0% to 82% of infants met the current adequate recommendations at varying periods of lactation. The calculated macro- and trace-element intakes were below the adequate intake recommendations, suggesting that they are not reflective of healthy infant requirements. These findings suggest the need for larger studies using sensitive analytical techniques and the revision of current recommendations for breastfed infants.

Reduction in Maternal Energy Intake during Lactation Decreased Maternal Body Weight and Concentrations of Leptin, Insulin and Adiponectin in Human Milk without Affecting Milk Production, Milk Macronutrient Composition or Infant Growth.

Maternal diet has the potential to affect human milk (HM) composition, but very few studies have directly assessed the effect of maternal diets on HM composition. The primary aim of this study was to assess the effect of improving dietary quality in lactating women over 2 weeks on the concentrations of macronutrients and metabolic hormones in HM. The secondary aims were to assess the impact of the dietary intervention on 24 h milk production, maternal body composition and infant growth. Fifteen women completed a 1-week baseline period followed by a 2-week dietary intervention phase targeted towards reducing fat and sugar intake. Maternal anthropometric and body composition and infant growth measurements were performed weekly. Total 24 h milk production was measured before and after the dietary intervention, and HM samples were collected daily. Maternal intakes of energy (-33%), carbohydrate (-22%), sugar (-29%), fat (-54%) and saturated fat (-63%) were significantly reduced during the dietary intervention. HM insulin, leptin and adiponectin concentrations were 10-25% lower at the end of the dietary intervention, but HM concentrations of macronutrients were unaffected. Maternal body weight (-1.8%) and fat mass (-6.3%) were significantly reduced at the end of the dietary intervention, but there were no effects on 24 h milk production or infant growth. These results suggest that reducing maternal energy, carbohydrate, fat and sugar intake over a 2-week period is associated with significant reductions in HM insulin, leptin and adiponectin concentrations. These changes may be secondary to decreases in maternal weight and fat mass. The limited studies to date that have investigated the association between metabolic hormone concentrations in HM and infant growth raise the possibility that the changes in HM composition observed in the current study could impact infant growth and adiposity, but further studies are required to confirm this hypothesis.

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).

Human milk immunomodulatory proteins are related to development of infant body composition during the first year of lactation.

BACKGROUND: To investigate relationships between infant body composition (BC) and human milk (HM) immunomodulatory proteins (IMPs) during the first 12 months of lactation. METHODS: BC of breastfeeding dyads (n = 20) was measured with ultrasound skinfolds (infants) and bioimpedance spectroscopy (infants/mothers) at 2, 5, 9, and/or 12 months post partum. Breastfeeding frequency, 24-h milk intake, and IMP concentrations (lactoferrin, lysozyme, secretory immunoglobulin A (sIgA)) were measured, and calculated daily intakes (CDIs) were determined. We used linear regression/mixed-effects models and adjusted results for multiple comparisons. RESULTS: No associations were seen between maternal characteristics and IMP concentrations/CDIs or between IMP concentrations and infant BC. Lactoferrin CDI was negatively associated with infant fat-free mass index (P = 0.002); lysozyme CDI was positively associated with infant fat mass (P = 0.004) and fat mass index (P = 0.004) measured with ultrasound skinfolds. CONCLUSION: In this small cohort of infants breastfed on demand during first year of life, we report differential associations of HM IMPs with infant BC, showing that in addition to their critical role in shaping infant immunity, lactoferrin, and lysozyme also influence development of infant BC, highlighting the importance of breastfeeding for 12 months and beyond. IMPACT: HM IMPs (concentrations and, most importantly, daily intakes) time-dependently and differentially associate with development of infant lean mass and adiposity during first 12 months of lactation. There is no information on how intakes and concentrations of these components affect development of infant BC. HM contains IMPs-lactoferrin, lysozyme, and sIgA, which not only play a critical role in shaping infant's immunity, but also influence infant growth and development of BC, highlighting the importance of breastfeeding for 12 months and beyond and warranting careful consideration of the dose effects of supplemented formula.

Excessive Weight Gain Followed by Catch-Down in Exclusively Breastfed Infants: An Exploratory Study.

Some infants experience excessive weight gain (EWG) during exclusive breastfeeding, but causes and consequences are unknown. The objective was to identify factors associated with early EWG. Infants with EWG (HW-group) were examined at 5, 9 and 18 mo and compared to a breastfed group with normal weight gain (NW-group). Anthropometry, body composition, milk and blood samples, and milk intake were measured. Mean body-mass-index-for-age z-scores (BAZ) increased 1.93 from birth to 5 mo in the HW-group (n = 13) while the NW-group (n = 17) was unchanged (-0.01). The HW-group had 70% more fat mass at 5 mo, and then showed marked catch-down in BAZ from 5 to 18 mo (-0.84). Milk intake at 5⁻6 mo did not differ between the groups. In the HW-group milk-leptin was lower at 5 mo and serum-leptin was considerably higher at 5 and 9 mo compared to the NW-group. Serum-leptin at 5 mo was positively associated with weight-for-age z-score (WAZ) and fat mass and negatively with WAZ change from 5 to 9 mo. In conclusion, breastfed infants with EWG had catch-down growth when other foods were introduced. Low milk-leptin in the HW-group may have stimulated appetite and milk intake when weight gain was high. High serum-leptin in the HW-group suggests early leptin resistance, which could impact cerebral regulation of energy intake. Larger studies are needed to confirm these results.

Relationships between Breastfeeding Patterns and Maternal and Infant Body Composition over the First 12 Months of Lactation.

Breastfeeding has been implicated in the establishment of infant appetite regulation, feeding patterns and body composition (BC). A holistic approach is required to elucidate relationships between infant and maternal BC and contributing factors, such as breastfeeding parameters. Associations between maternal and breastfed term infant BC (n = 20) and feeding parameters during first 12 months of lactation were investigated. BC was measured at 2, 5, 9 and/or 12 months postpartum with ultrasound skinfolds (US; infants only) and bioimpedance spectroscopy (infants and mothers). 24-h milk intake (MI) and feeding frequency (FFQ) were measured. Higher FFQ was associated with larger 24-h MI (p ≤ 0.003). Higher 24-h MI was associated with larger infant fat mass (FM) (US: p ≤ 0.002), greater percentage FM (US: p ≤ 0.008), greater FM index (FMI) (US: p ≤ 0.001) and lower fat-free mass index (FFMI) (US: p = 0.015). Lower FFQ was associated with both larger FFM (US: p ≤ 0.001) and FFMI (US: p < 0.001). Greater maternal adiposity was associated with smaller infant FFM measured with US (BMI: p < 0.010; %FM: p = 0.004; FMI: p < 0.011). Maternal BC was not associated with FFQ or 24-h MI. These results reinforce that early life is a critical window for infant programming and that breastfeeding may influence risk of later disease via modulation of BC.

Changes in Fatty Acid Composition of Human Milk in Response to Cold-Like Symptoms in the Lactating Mother and Infant.

Infants rely on their innate immune systems to protect them from infection. Human milk (HM) contains fatty acids (FAs) and monoacylglycerols that are known to exhibit antiviral and antibacterial properties in vitro. The specific fat content of HM may potentially affect the efficacy of this antimicrobial activity. This preliminary study investigates whether the proportions of FA in HM change in response to infections, leading to cold-like symptoms in the mother or infant. Milk samples were obtained from mothers (n = 26) when they and their infants were healthy, and when mother, infant, or both suffered cold-like symptoms. The milk was hydrolysed and FA proportions were measured using gas chromatography. Fifteen FAs were recorded, of which eight were detected in sufficient quantities for statistical analysis. The proportions of capric (C10:0) and lauric acids (C12:0) in HM were significantly lower, and palmitic acid (C16:0) was higher when mothers and infants were ill compared to healthy samples. Palmitoleic (C16:1, n-7) and stearic acid (C18:0) proportions were higher in HM when the infant was unwell, but were not related to maternal health. Whilst the differences detected were small (less than 0.5%), the effects may be additive and potentially have a protective function. The value of further studies is certainly indicated.

The relationship of human milk leptin and macronutrients with gastric emptying in term breastfed infants.

BackgroundInfants breastfed on demand exhibit a variety of feeding patterns and self-regulate their nutrient intake, but factors influencing their gastric emptying (GE) are poorly understood. Despite research into appetite regulation properties of leptin, there is limited information about relationships between human milk leptin and infant GE.MethodsGastric volumes were calculated from ultrasound scans of infants' stomachs (n=20) taken before and after breastfeeding, and then every 12.5 min (median; range: 3-45 min) until the next feed. Skim milk leptin and macronutrient concentrations were measured and doses were calculated.ResultsThe leptin concentration was (mean±SD) 0.51±0.16 ng/ml; the leptin dose was 45.5±20.5 ng per feed. No relationships between both concentration and dose of leptin and time between the feeds (P=0.57; P=1, respectively) or residual stomach volumes before the subsequent feed (P=0.20; P=0.050) were found. Post-feed stomach volumes (GE rate) were not associated with leptin concentration (P=0.77) or dose (P=0.85).ConclusionGE in term breastfed infants was not associated with either skim milk leptin concentration or dose. Further investigation with inclusion of whole-milk leptin and other hormones that affect gastrointestinal activity is warranted.

Associations between Maternal Body Composition and Appetite Hormones and Macronutrients in Human Milk.

Human milk (HM) appetite hormones and macronutrients may mediate satiety in breastfed infants. This study investigated associations between maternal adiposity and concentrations of HM leptin, adiponectin, protein and lactose, and whether these concentrations and the relationship between body mass index and percentage fat mass (%FM) in a breastfeeding population change over the first year of lactation. Lactating women (n = 59) provided milk samples (n = 283) at the 2nd, 5th, 9th and/or 12th month of lactation. Concentrations of leptin, adiponectin, total protein and lactose were measured. Maternal %FM was measured using bioimpedance spectroscopy. Higher maternal %FM was associated with higher leptin concentrations in both whole (0.006 ± 0.002 ng/mL, p = 0.008) and skim HM (0.005 ± 0.002 ng/mL, p = 0.007), and protein (0.16 ± 0.07 g/L, p = 0.028) concentrations. Adiponectin and lactose concentrations were not associated with %FM (0.01 ± 0.06 ng/mL, p = 0.81; 0.08 ± 0.11 g/L, p = 0.48, respectively). Whole milk concentrations of adiponectin and leptin did not differ significantly over the first year of lactation. These findings suggest that the level of maternal adiposity during lactation may influence the early appetite programming of breastfed infants by modulating concentrations of HM components.

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 24 hour period. Twenty three exclusively breastfeeding mothers collected milk, prior to and after each breastfeeding session over 24 hour 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 (3.40 ng/ml), and cortisol was detected in all samples (1.62 ng/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 (2.97 ng/ml and 4.88 ng/ml), compared to afternoon (1.20 ng/ml and 3.54 ng/ml), evening (0.69 ng/ml and 2.13 ng/ml) and night (1.59 and 3.27 ng/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 24 hour 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.

Determinants of body composition in breastfed infants using bioimpedance spectroscopy and ultrasound skinfolds-methods comparison.

BACKGROUND: Accurate, noninvasive, and inexpensive methods are required to measure infant body composition. Ultrasound (US) and bioimpedance spectroscopy (BIS) have been validated in adults and introduced in pediatric populations. The aim of this study was to evaluate the performance of both methods in determining percentage fat mass (%FM) in breastfed infants. METHODS: %FM of 2, 5, 9, and 12 mo-old healthy, breastfed term infants (n = 58) was calculated using BIS-derived total body water equations and skinfold equations then compared with reference models. Skinfolds were measured with US at two and four sites (biceps, suprailiac and/or triceps, and subscapular). RESULTS: %FM differed widely within and between methods, with the degree of variation affected by infant age/sex. Not a single method/equation was consistent with the distributions of appropriate reference values for all age/sex groups. Moderate number of matches with references values (13-24 out of 36) was seen for both types of equations. High number of matches (25-36) was seen for US skinfold-based equations. %FM values calculated from US and BIS were not significantly different (P = 0.35). CONCLUSION: Both BIS and US are practical for predicting %FM in infants. BIS calculations are highly dependent upon an appropriate set of validated age-matched equations.

Effect of Human Milk Appetite Hormones, Macronutrients, and Infant Characteristics on Gastric Emptying and Breastfeeding Patterns of Term Fully Breastfed Infants.

Human milk (HM) components influence infant feeding patterns and nutrient intake, yet it is unclear how they influence gastric emptying (GE), a key component of appetite regulation. This study analyzed GE of a single breastfeed, HM appetite hormones/macronutrients and demographics/anthropometrics/body composition of term fully breastfed infants (n = 41, 2 and/or 5 mo). Stomach volumes (SV) were calculated from pre-/post-feed ultrasound scans, then repeatedly until the next feed. Feed volume (FV) was measured by the test-weigh method. HM samples were analyzed for adiponectin, leptin, fat, lactose, total carbohydrate, lysozyme, and total/whey/casein protein. Linear regression/mixed effect models were used to determine associations between GE/feed variables and HM components/infant anthropometrics/adiposity. Higher FVs were associated with faster (-0.07 [-0.10, -0.03], p < 0.001) GE rate, higher post-feed SVs (0.82 [0.53, 1.12], p < 0.001), and longer GE times (0.24 [0.03, 0.46], p = 0.033). Higher whey protein concentration was associated with higher post-feed SVs (4.99 [0.84, 9.13], p = 0.023). Longer GE time was associated with higher adiponectin concentration (2.29 [0.92, 3.66], p = 0.002) and dose (0.02 [0.01, 0.03], p = 0.005), and lower casein:whey ratio (-65.89 [-107.13, -2.66], p = 0.003). FV and HM composition influence GE and breastfeeding patterns in term breastfed infants.

Longitudinal study of pesticide residue levels in human milk from Western Australia during 12 months of lactation: Exposure assessment for infants.

The presence of pesticides in human milk (HM) is of great concern due to the potential health effects for the breastfed infant. To determine the relationships between HM pesticides and infant growth and development, a longitudinal study was conducted. HM samples (n = 99) from 16 mothers were collected at 2, 5, 9 and 12 months of lactation. A validated QuEChERS method and Gas chromatography-tandem mass spectrometry (GC-MS/MS) were used for the analysis of 88 pesticides in HM. Only p,p'-DDE, p,p'-DDT and ß-HCH were detected with a mean concentration (±SD) of 52.25 ± 49.88 ng/g fat, 27.67 ± 20.96 ng/g fat and 48.00 ± 22.46 ng/g fat respectively. The concentrations of the detected pesticides decreased significantly throughout the first year of lactation. No significant relationships between HM p,p'-DDE and infant growth outcomes: weight, length, head circumference and percentage fat mass were detected. The actual daily intake (ADI) of total DDTs in this cohort was 14-1000 times lower than the threshold reference and significantly lower than the estimated daily intake (EDI). Further, the ADI decreased significantly throughout the first 12 months of lactation.

Case report of nipple shield trauma associated with breastfeeding an infant with high intra-oral vacuum.

BACKGROUND: Nipple pain is associated with early cessation of breastfeeding and may be caused by high intra-oral vacuum. However identification of high intra-oral vacuum is typically restricted to the research setting. This is the first reported case of an infant with high intra-oral vacuum that was clinically identified through a specific pattern of nipple trauma associated with nipple shield use. Knowledge of clinical signs associated with high intra-oral vacuum may facilitate early recognition of this unusual breastfeeding challenge. CASE PRESENTATION: The mother of an exclusively breastfed 3 month old infant had severe bilateral nipple pain with minimal trauma that persisted from birth. The nipples were not misshapen immediately after breastfeeding and adjustments to infant attachment at the breast did not attenuate the pain. Examination of the infant's oral anatomy was unremarkable with no ankyloglossia present. Microbiological cultures of nipple swabs and breast milk were negative for bacterial and fungal growth, and prescribed antimicrobial treatments did not reduce the nipple pain. Mild blanching and erythema of the nipples were occasionally observed, and were not consistent with nipple vasospasm. Nipple shields were used regularly as they modified the pain, although this resulted in blisters that corresponded with the nipple shield holes. Measurement of infant intra-oral vacuum during breastfeeding confirmed intra-oral vacuum up to 307 % higher than reference values. Breastfeeding gradually became less painful, and after 6 months was completely comfortable. CONCLUSIONS: High intra-oral vacuum is difficult to assess in the clinical setting and is likely an under-reported cause of early weaning that is not well understood. This original case report highlights high intra-oral vacuum as at differential diagnosis to be considered by health professionals when evaluating mothers experiencing strong nipple pain during the initiation of breastfeeding. A clinical screening tool is needed to enable prompt identification of these infants.

Variation in fat, lactose, and protein composition in breast milk over 24 hours: associations with infant feeding patterns.

BACKGROUND: Data regarding the association between breast milk composition and infant feeding patterns (frequency and amount of breast milk taken) would help in understanding the regulation of food intake in breastfed infants. OBJECTIVE: This study examined the relationship between breast milk macronutrient concentration and patterns of milk intake in breastfeeding infants over a 24-hour breastfeeding period. METHODS: Mothers of healthy term infants (n = 15) collected pre- and postfeed breast milk samples from each feed at each breast over a 24-hour period. Breast milk samples were analyzed for fat, lactose, total protein, casein, and whey protein content. The energy content for each feed was calculated. RESULTS: Breastfeeding patterns and milk composition varied greatly between individuals. The fat content of milk significantly differed over 24 hours (P = .01), whereas the concentration of lactose and protein content remained the same. The mean 24-hour total protein, whey, and casein intake was inversely (P < .01), whereas lactose concentration was positively (P = .03) related to the number of breast feeds per day. No relationship was seen either between fat or energy content and feeding patterns. The mean (SD) concentration of fat, lactose, and total protein over the 24-hour period was 43 (12) g/L, 68 (7) g/L, and 13 (2) g/L, respectively. CONCLUSION: The association between milk protein intake and the breastfeeding frequency suggests that the protein intake may play a role in infant appetite control.

Investigation of short-term variations in casein and whey proteins in breast milk of term mothers.

OBJECTIVES: We investigated changes in breast milk whey and casein proteins, between fore and hind milk during breast expression, between breasts and within 24-hour period during breast-feeding. This has implications for developing an appropriate sampling protocol for investigating the influence of milk composition on gastric emptying and infants' feeding behaviour. METHODS: Breast milk samples were collected from mothers (n = 25) of healthy term infants ages 1 to 8 months. A total of 17 mothers provided fore and hind milk samples, which were collected during simultaneous expression of both breasts. Fifteen mothers provided samples from each breast-feed during 24-hour period, of which samples were selected from 4 time points (morning, day, evening, night). Whey and casein were isolated from skim milk, and protein concentration of the skim, whey, and casein fractions were determined. RESULTS: Mean protein concentrations were found to be 13.5 ± 2.1 (skim milk), 7.6 ± 1.5 (whey), and 3.4 ± 0.97 g/L (casein). Protein concentrations were not significantly different between fore and hind milk. During a 24-hour period, no significant differences were found in protein concentration of any fraction at the 4 time points or between left and right breasts. Large variations were seen between mothers with coefficient of variances of 15.5%, 19.8%, and 28.4% for skim milk, whey, and casein, respectively. CONCLUSIONS: Although there was wide variation between mothers, the small variations within mothers indicate that for sampling purposes, a single breast milk sample (fore or hind from each breast at any time point of the day) will be representative of that mother's protein concentration of skim, whey, and casein fractions for that day.

Evaluation of a mid-infrared analyzer for the determination of the macronutrient composition of human milk.

A mid-infrared human milk analyzer (HMA) is designed to measure the macronutrients in human milk over a wide range of concentrations. Human milk samples (N = 30, 4 different dilutions each) were used to compare the macronutrient levels determined by the HMA to those derived from traditional laboratory methods. There was a small but statistically significant difference in the levels of fat, protein, lactose, total solids, and energy for all samples. These differences were consistent with subtle differences in the chemical principles governing the assays. For higher macronutrient levels, a trend to greater differences between the HMA and the laboratory method was seen, particularly in samples with high fat concentration. The intra-assay variation for the HMA for all macronutrients was less than 4%. It is concluded that that with appropriate sample preparation, the mid-infrared HMA can provide a practical measurement of macronutrients in human milk.