Breast feeding: benefits and hazards. Methodology and summary of results.
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Breast Feeding↗
Biomedical subjects
I S Rogers
Publications and source records attributed to I S Rogers.
Properties of human milk and their relationship with maternal nutrition.
The composition of human milk varies over the course of lactation and in each individual. The volume of breast milk produced is related to the weight of the infant. Human milk is markedly different from cows' milk, both in terms of macronutrients and micronutrients. This includes the types of fatty acids present and factors affecting their absorption. The types of proteins present and their relative proportions and both qualitative and quantitative differences in the non-protein nitrogen fraction. There is much less lactose in cows' milk than breast milk and the oligosaccharide fraction is very different. Their are major differences in content and absorption rates of vitamins and minerals from breast milk compared to cows' milk or formula milk. Vitamin D and vitamin K status are possible problems for the breast-fed infant in certain circumstances. The nutritional status of the mother appears to influence fat concentration and thus the energy content of breast milk as well as its fatty acid composition and immunological properties. There is no coherent evidence, however, that the protein or lactose concentrations are greatly affected. There is some evidence that the concentration of vitamins in the breast milk are influenced by the mother's intake. Minerals are less variable, with the exception of selenium. The response of the infant to human and formula milk differs with respect to endocrine function, stool motility, immune function and renal function. Infant formula milks are designed to mimic human milk as much as possible, but this is unlikely to ever be completely successful. A number of important compositional differences between human milk and formula milk remain. This includes the types and proportions of fatty acids present (which may be of developmental importance), the nature of the non-protein nitrogen component (also possible developmental importance) and the presence of immunoglobulins and fibronectin (which may protect the infant against infection).
Diet↗
The incidence and duration of breast feeding.
Information obtained from a variety of sources shows different rates of initiation and duration of breast feeding and different supplementation strategies. Among populations of developing countries, in general, the mothers resident in rural-areas are more likely to breast feed than those in urban areas; in addition the better off or more highly educated are less likely to breast feed. In contrast in the developed countries, the better educated and the higher social class mothers are more likely to breast feed. There is some evidence that delay in initiation of breast feeding, lack of professional support, conflicting advice from health professionals and the presence of free samples of artificial milk (whether or not given to the mother) can result in a mother failing to establish breast feeding. Additionally, mothers who smoke cigarettes are less likely to breast feed successfully. Whilst breast feeding is almost universal in a number of developing countries, many also commonly use complementary feeds. In some countries, particularly in Asia, it is still commonplace for a child not to be given the mother's colostrum, and therefore for the first breast feed to occur well after the first 24 h.
Attitude↗
Relactation.
Relactation may be useful in the developing world either if the child has been ill and unable to feed for a time or the mother is ill or has died. Relactation appears to be easier with a younger infant and in women who have lactated previously. However, with appropriate care, support and motivation even some women who have never been pregnant or who have been pregnant but never lactated may be able to start lactation.
Adoption↗
Gastroenteritis, diarrhoea and breast feeding.
In this paper we review the literature in regard to possible relationships between breast feeding and diarrhoea or gastroenteritis. We show that in the developed as well as the developing world, there is consistent evidence of a protective effect of exclusive breast feeding in the first 4-6 months of life. The odds ratios were generally in excess of 3.0 for non-breast milk feeds. The relationship was not consistent for rotavirus infections but was consistently strong for non-viral pathogens. There are a number of indicators that suggest biological plausibility, in both the developing and developed world. The triple indicators of consistency and strength of the epidemiological associations, together with biological plausibility are major arguments for believing that there is a causal sequence involved.
Breast Feeding↗
Does breast feeding protect against non-gastric infections?
There is convincing evidence that breast-feeding is protective against gastro-enteritis and diarrhoea, but for other infections the situation is less clear cut. There is evidence that breast-fed infants are at increased risk of one infection (infant botulism). They are probably not significantly protected from upper respiratory tract infections (other than otitis media.), but they may be at a decreased risk of lower respiratory tract infections, particularly those associated with respiratory syncytial virus. There is strong evidence that Haemophilus influenzae B infection is more likely in the bottle-fed infant, and consistent evidence of protection of young children from chronic otitis media with prolonged breast-feeding.
Breast Feeding↗
Eczema, asthma and allergy.
The literature in relation to the development of atopic and allergic disorders has been reviewed, in order to assess the claim that prolonged and exclusive breast feeding protects against the development of such disorders. The data in the literature show little consistent evidence to identify any protective association between breast feeding and either eczema, wheezing/asthma or other types of atopy or allergic response.
Asthma↗
Does breast feeding have any impact on non-infectious, non-allergic disorders?
Feeding of breast milk in the first weeks of life appears to have a strong protective effect against necrotising enterocolitis. Nevertheless breast milk also seems to be positively linked to the development of jaundice and to late haemorrhagic disease in infants who have not received vitamin K supplements. There is no consistent evidence that other childhood conditions such as insulin dependent diabetes or cancer are less prevalent among children who have been breast fed. Among adult conditions suggested to be less prevalent in the breast fed, only single reports of significant findings for multiple sclerosis and breast cancer exist and convincing corroboration is not available. There are a number of studies that indicate a relationship between breast feeding and later cholesterol levels--and one that has considered the mortality of ischaemic heart disease among adult males. There is some suggestion that breast feeding (during the first year of life) is the optimal protection against future raised lipid levels and mortality from coronary heart disease, but the evidence is far from conclusive. The major health advantage of breast feeding that has been clearly demonstrated remains in the protection of the infant from certain infections in early life. If there are other long-term health advantages they have yet to be fully elucidated and confirmed.
Adult↗
Breast feeding and infant mortality.
The evidence linking bottle feeding to infant and early childhood mortality has been reviewed. Ecological studies of national time trends in infant mortality do not parallel breast feeding trends in those countries, and indicate that falling death rates are more likely to be related to better health care facilities and social conditions. Direct studies of deaths provide some contradictory findings; meta-analyses are not informative because of the many differences in statistical and sample methodology. The methodology exhibited in most studies is more likely to have over- rather than under-estimated a relationship between bottle feeding and infant mortality. Retrospective analyses must take account of changes in feeding pattern due to early signs of illness. Prospective population studies able to account for large numbers of potential confounders provide the best estimates, especially if proportional hazards models are used. Two such studies have been carried out--both showed protective effects of breast feeding.
Breast Feeding↗
The growth and nutritional status of the breast-fed infant.
The literature on the relationship between early infant feeding and growth shows that after the first 3 or 4 months, breast-fed infants in the developed world are lighter than formula-fed infants with markedly lower adiposity. There is some evidence of a slightly lower rate of linear growth over the first year or so. These differences in weight and length do not apparently persist beyond the first few years of life. In the developing world the situation is very different. The growth curves of breast-fed infants of malnourished mothers may falter between the third and sixth month of life. However, the generally poor quality of the supplementary foods offered in the developing world and the increased risk of diarrhoeal infections mean that supplementary feeding before the age of 6 months is unlikely to lead to a growth advantage and may well lead to growth faltering.
Breast Feeding↗
Association between breast feeding, child development and behaviour.
Consistent data are available to suggest that children who have been breast fed are, on average, intellectually more able than their formula-fed contemporaries. This has been shown in eight of 10 population studies and all three studies of low birthweight infants. In general, the longer the child has been breast fed the more pronounced the effect. There is evidence that breast milk that has been pasteurised before feeding does not have this effect, but that fresh breast milk is effective whether the milk is delivered by tube or by the breast. However no studies have been able to have both sufficient statistical power and the ability to allow for other confounders such as parental ability, parental IQ and other factors that might explain these findings. Additional data from studies of visual acuity show an association between breast feeding and enhanced vision which is hypothesised to be due to the unique fatty acid composition of breast milk. The differences in intellectual development might also be related to these fatty acids. Alternative explanations for the effect on intellectual development concern the possible consequences of early infections, particularly gastroenteritis, which are more common in bottle-fed babies. In contrast with the many publications on cognitive function and breast feeding, there was only one on neurological dysfunction (showing a protective effect of breast feeding) and one on childhood behaviour (using the teacher's assessment no relationship with breast feeding was found). Further research is needed in both areas.
Breast Feeding↗
Lactation and fertility.
Breastfeeding suppresses ovarian activity resulting in amenorrhea and infertility. The frequency of breastfeeds and their duration appear to be important in maintaining amenorrhea--and night-time sucking appears to be particularly crucial. Supplementary feeding may affect fertility by altering suckling behaviour, but the evidence is confusing as to whether feeding supplements reduces the duration of amenorrhea and increases the risk of conception. Mothers who are better nourished tend to have a shorter period of amenorrhea than the malnourished, possibly because the infant has to suckle for a shorter period to obtain the nourishment needed. Lactation has an important effect on fertility at the population level. However, it cannot be considered a reliable contraceptive at an individual level.
Amenorrhea↗
The effects of lactation on the mother.
Undernourished mothers are likely to have limited fat reserves to draw on during lactation. In order to supply nutrition to her child the mother may therefore become more malnourished and suffer from bone resorption. Repeated or overlapping pregnancies with lactation are likely to compound the issue. Little research has been carried out into the health of mothers while breast feeding, or subsequently. There are theoretical reasons to think that the malnourished mother in the developing world may be particularly vulnerable, but no studies appear to have been undertaken. Investigations in the developed world have concentrated on cancers of the reproductive organs and shown consistent evidence in large case-control studies for a reduced risk of pre-menopausal breast cancer in mothers with a history of prolonged breast feeding. In contrast there have been a number of studies in the developed world concerned with emotional well-being with some indications that mothers who breast feed are more likely to be depressed and are less likely to be positive about their baby.
Female↗