Milk taken by human babies from the first and second breast

Barriers and enablers to Caregivers Responsive feeding Behaviour (CRiB): A mixed method systematic review protocol

Background: Childhood overweight and obesity is a major public health issue. Responsive feeding has been identified as having a protective effect against child overweight and obesity, and is associated with healthy weight gain during infancy. Responsive feeding occurs when the caregiver recognises and responds in a timely and developmentally appropriate manner to infant hunger and satiety cues. Despite its benefits, responsive feeding is not ubiquitous. To better support caregivers to engage in responsive feeding behaviours, it is necessary to first systematically identify the barriers and enablers associated with this behaviour. This mixed-methods systematic review therefore aims to synthesise evidence on barriers and enablers to responsive feeding using the COM-B model of behavioural change. Methods: 7 electronic databases will be searched (Maternal and Infant Care, CINAHL, Cochrane, PubMed, Medline, PsycINFO, EMBASE). Studies examining factors associated with parental responsive and non-responsive feeding of infants and children (<2 years) will be included. Papers collecting primary data, or analysing primary data through secondary analysis will be included. All titles, abstracts and full texts will be screened by two reviewers. Quantitative and qualitative data from all eligible papers will be independently extracted by at least two reviewers using pre-determined standardised data extraction forms. Two reviewers will independently assess the methodological quality of the studies using the Mixed Methods Appraisal Tool (MMAT). This review will be reported according to the Preferred Reporting Items for Systematic reviews and Meta Analyses (PRISMA). Ethics and dissemination: Ethical approval is not required for this review as no primary data will be collected, and no identifying personal information will be present. The review will be disseminated in a peer reviewed journal. PROSPERO registration: CRD42019144570 (06/08/2019).

Barriers and enablers to Caregivers Responsive feeding Behaviour (CRiB): A mixed method systematic review protocol

Background: Childhood overweight and obesity is a major public health issue. Responsive feeding has been identified as having a protective effect against child overweight and obesity, and is associated with healthy weight gain during infancy. Responsive feeding occurs when the caregiver recognises and responds in a timely and developmentally appropriate manner to infant hunger and satiety cues. Despite its benefits, responsive feeding is not ubiquitous. To better support caregivers to engage in responsive feeding behaviours, it is necessary to first systematically identify the barriers and enablers associated with this behaviour. This mixed-methods systematic review therefore aims to synthesise evidence on barriers and enablers to responsive feeding using the COM-B model of behavioural change. Methods: 7 electronic databases will be searched (Maternal and Infant Care, CINAHL, Cochrane, PubMed, Medline, PsycINFO, EMBASE). Studies examining factors associated with parental responsive and non-responsive feeding of infants and children (<2 years) will be included. Papers collecting primary data, or analysing primary data through secondary analysis will be included. All titles, abstracts and full texts will be screened by two reviewers. Quantitative and qualitative data from all eligible papers will be independently extracted by at least two reviewers using pre-determined standardised data extraction forms. Two reviewers will independently assess the methodological quality of the studies using the Mixed Methods Appraisal Tool (MMAT). This review will be reported according to the Preferred Reporting Items for Systematic reviews and Meta Analyses (PRISMA). Ethics and dissemination: Ethical approval is not required for this review as no primary data will be collected, and no identifying personal information will be present. The review will be disseminated in a peer reviewed journal. PROSPERO registration: CRD42019144570 (06/08/2019).

The Many Axes of Deer Lactation

In undomesticated animals information about the production and composition of milk over time is still scarce. In general, for most mammals it is known that milk composition changes across lactation, is different for male and female offspring, and even that marsupials, such as kangaroos, can simultaneously produce milk of different compositions for young of different ages. Such parallel milk production of differing compositions has not yet been studied in single-offspring placental mammals, but may help to explain behavioural processes like allosuckling (feeding the young of other adults) and lateralized suckling preferences. In this study we analysed the production and composition of milk in red deer throughout the lactation period and now confirm for the first time that there are axial differences present. The front teats, which are the favoured suckling positions of the deer's offspring, produce milk with a greater protein-to-fat ratio. Also, from the beginning of lactation the yield is greater on the left side, the side preferred by calves in all of the studied species, both at population and individual level. The links between milk production and calf behaviour in deer deserve further study.

Energy intake, appetite and body mass in infancy

Energy intake in infancy depends on the infant's appetite, which, in turn, depends to a considerable extent on the infant's size, as size is an important determinant of energy expenditure. Previous work on six-week old breast-fed infants has suggested that, at this age, milk intake in infants is proportional to the square root of body weight (wt.(0.5)). In this paper, the form of the relationship between body weight and energy intake is examined in infants of different ages, using data from two longitudinal studies, one of initially breast-fed and one of initially bottle-fed infants. In the first data set, energy intake is proportional to body weight raised to powers ranging from 0.63 to 1.23 at different ages and, in the second, to body weight raised to powers ranging from 0.50 to 1.07 at different ages. No single value is consistent with all the data at all ages. In general, the powers decrease up to six months of age, and then increase again, a pattern that may be due to the pattern of changes in the adiposity of the infants, as reflected in their body mass indexes (BMIs).

Is suckling behaviour a useful predictor of milk intake? A review

In studies on mammalian parental investment, time spent suckling is often used as a predictor of the milk transferred from mother to infant. It is assumed that the rate of milk transfer is positively correlated with the time spent suckling. However, this assumption has not been tested and empirical studies show conflicting results. Nevertheless, in species in which suckling can readily be observed, time spent suckling is still used to measure milk transfer, although an increasing number of workers recognize that the measure is potentially inaccurate. A meta-analysis on studies that have correlated measures of time spent suckling with milk intake estimates based on weight gain revealed a weak positive relationship and significant heterogeneity between studies. Isotope-labelling techniques for the measurement of milk transfer independent of behaviour have been in use since the 1970s, particularly in studies of species in which suckling is difficult to observe. Only one study has attempted to correlate behavioural measures with independent isotope measures, and it found no relationship between the two measures. I suggest that researchers have avoided such a test as it is unlikely that a strong relationship will be found between milk transfer and suckling behaviour, and I discuss the various factors that confound the relationship and contribute to high heterogeneity between studies. Consequently, the assumption that milk transfer can be measured by time spent suckling has inadequate empirical foundation, and needs to be tested using isotope-labelling methods. Copyright 1998 The Association for the Study of Animal Behaviour

Recent advances in breast feeding

Increasingly, epidemiological studies are showing the benefits of exclusive breast-feeding to infants in industrialized countries, as they have previously for those in developing countries. In this review we have focused on several recent developments, in particular on the interplay between infant behaviour and maternal physiology in regulating breast milk supply. This will illustrate that many past and current clinical problems concerning breast-feeding are likely to be of iatrogenic origin, the products of imposing arbitrary rules for breast-feeding management. In order for the protective benefits to be fully realized it is necessary to ensure that breast-feeding is free from prescriptive practices. We will illustrate the key role played by the infants' control of appetite in the hope of encouraging clinicians to empower infants to exercise more control over the feeding process.

The Chiang Mai lactation project: study design and implementation

The Chiang Mai lactation project is a longitudinal field study of human lactation carried out among northern Thai women living in the Sanpatong area of Chiang Mai Province. Its aim was to measure the volume and composition of breast milk transferred from mothers to their infants in the first year postpartum, and to relate it to predictors of milk production, and to the growth of the child. Breast milk and supplementary food intake, and nursing patterns, were recorded over two consecutive 24-hour periods six times during the first year. Samples of breast milk and of supplementary foods were analysed for energy and protein. Supplementary foods were also analysed for bacterial contamination. The growth of the child was measured, and health assessed using a combination of health diaries and examination by a physician. Recruitment to the study was excellent. After recruitment, two subjects left the study area, but otherwise only two dropped out, so complete sets of data covering these variables are available for 58 of the 62 recruited subjects.

[Supply, metabolism and biological effects of trans-isomeric fatty acids in infants]

Consumption of trans-fatty acids increased markedly during this century due to the widespread use of partially hydrogenated fats. A sensitive analytical method was developed which enables the precise determination of 7 trans-isomers in small sample volumes. With this method we documented the materno-fetal transfer of trans-fatty acids across the human placenta. The content in human milk depends on maternal diet and is lower in Germany than in the Sudan. The distribution in fore- and hind-milk, in milk fat fractions and within the triglyceride molecule was determined. The content of trans-fatty acids is lower in commercial and home-made infant formulae than in human milk, although there is a certain batch to batch variation in formulae. Infants absorb dietary trans-isomers and incorporate them into endogenous lipids, subcutaneous tissue and cell membranes. Trans-fatty acids in plasma lipids are significantly higher in infants fed human milk than in those fed formulae. African children have a lower exposure than Germans. The relative contribution of trans-octadecenoic acid is lower in plasma sterol esters than in triglycerides and phospholipids, pointing to a negative selectivity of plasmatic cholesterol esterification with this fatty acid. Thus, a high supply of trans-octadecenoic acid might have negative effects on the cholesterol levels. In premature infants we found an inverse correlation between trans-fatty acid exposure and birthweight, thus interference with intrauterine growth appears possible. A possible causative factor could be impaired biosynthesis of long-chain polyunsaturated fatty acids by trans-isomers, for which we found strong indications. The results of our investigations the question whether the consumption of trans-fatty acids in pregnant and lactating women and in infants is nutritionally safe.

Do changes in pattern of breast usage alter the baby's nutrient intake?

Twelve mother/baby pairs took part in a study of the difference in effect of two patterns of breast feeding--either feeding at one breast or at two breasts during a feed. Baseline measures were taken at 4 weeks, and the test patterns of feeding were followed for a week each, in random order. The two patterns of feeding led to differences in milk volume intake and mean feed fat concentration, but not in the baby's net fat intake per 24 h. The results indicate that the breast-fed baby can regulate his fat intake quickly and thus mothers should be encouraged to practice "baby-led" feeding.

Circadian variation in fat concentration of breast-milk in a rural northern Thai population

1. Twenty-five northern Thai mothers, breast-feeding their infants on demand, were studied in their homes for 24 h. All breast-feeds were test-weighed and pre- and post-feed expressed breast-milk samples (0.5 ml) taken at each feed. 2. The fat concentration of milk taken during a feed showed significant circadian variation, with maximum values between 16.00 and 20.00 hours and minimum values between 04.00 and 08.00 hours. Fat concentration at the start and at the end of a feed also varied significantly over 24 h. 3. Multiple regression analysis showed that the most important predictor of fat concentration at a feed was the length of time elapsed since the previous feed--the longer this interval, the lower the subsequent fat concentration. Other significant predictors were the fat concentration at the end of the previous feed, and the milk intake at the previous and at the current feed. 4. Fat concentration declined between feeds in proportion to the length of time between feeds, but the decline was less between sleep feeds than between waking feeds. This would appear to be a reflection of the lower post-feed fat concentration and higher pre-feed fat concentration of sleep feeds compared with waking feeds, when other variables relating to feeding pattern are taken into account. 5. The larger the milk intake at a feed, the greater was the increase in fat concentration from the start to the end of the feed. The change in fat concentration was less in feeds taking place during the sleep period than in daytime feeds.

Milk flow and sucking rates during breast-feeding

This study examined sucking patterns during breast-feeding in order to investigate the supposed 'nutritive' and 'non-nutritive' sucking dichotomy. The intervals between sucks were determined: they indicated that there is no bimodal distribution corresponding to 'nutritive' and 'non-nutritive' rates of sucking, but rather a complete gradation between the two. In a further experiment in which milk flow was assessed by test-weighing the baby at three-minute intervals during feeding, there was a linear relationship between milk flow and sucking rate: the higher the milk flow, the lower the sucking rate. These results were further substantiated by testing the sucking rate on an empty and full breast, and the sucking pattern of an infant with a non-lactating mother. The study shows that there is no dichotomy between two sucking rates, but rather a continuous variation in response to milk-flow rate.

The continuous measurement of milk intake at a feed in breast-fed babies

A method for the continuous measurement of milk intake during a breast-feed is described. A miniature Doppler ultrasound flow transducer, located in the tip of a latex nipple shield, is interposed between mother and baby during feeding. Preliminary results indicate the scope and current limitations of the method in terms of both populations and individual mother/infant pairs. An initial analysis of individual feeds indicates that two factors may contribute to the curtailment of intake during a feed from one breast: a progressive reduction in intake volume per suck, and/or an increase in the proportion of time spent pausing between bursts of sucking.