The physiological basis of breastfeeding Z NOISS3S 2.1 Breast-milk composition a baby.The concentration of protein in breast milk Breast milk contains all the nutrients that an infant (0.9 g per 100 ml)is lower than in animal milks.The needs in the first 6 months of life,including fat,car- much higher protein in animal milks can overload bohydrates,proteins,vitamins,minerals and water the infant's immature kidneys with waste nitrogen (1,2,3,4).It is easily digested and efficiently used. products.Breast milk contains less of the protein Breast milk also contains bioactive factors that aug- casein,and this casein in breast milk has a different ment the infant's immature immune system,provid- molecular structure.It forms much softer,more eas- ing protection against infection,and other factors ily-digested curds than that in other milks.Among that help digestion and absorption of nutrients. the whey,or soluble proteins,human milk contains more alpha-lactalbumin;cow milk contains beta- Fats lactoglobulin,which is absent from human milk and to which infants can become intolerant (4). Breast milk contains about 3.5 g of fat per 100 ml of milk,which provides about one half of the energy Vitamins and minerals content of the milk.The fat is secreted in small drop- lets,and the amount increases as the feed progresses. Breast milk normally contains sufficient vitamins for As a result,the hindmilk secreted towards the end of an infant,unless the mother herself is deficient (5). a feed is rich in fat and looks creamy white,while the The exception is vitamin D.The infant needs expo- foremilk at the beginning of a feed contains less fat and sure to sunlight to generate endogenous vitamin D- looks somewhat bluish-grey in colour.Breast-milk or,if this is not possible,a supplement.The minerals fat contains long chain polyunsaturated fatty acids iron and zinc are present in relatively low concentra- (docosahexaenoic acid or DHA,and arachidonic acid tion,but their bioavailability and absorption is high or ARA)that are not available in other milks.These Provided that maternal iron status is adequate,term fatty acids are important for the neurological devel- infants are born with a store of iron to supply their opment of a child.DHA and ARA are added to some needs;only infants born with low birth weight may varieties of infant formula,but this does not confer need supplements before 6 months.Delaying clamp- any advantage over breast milk,and may not be as ing of the cord until pulsations have stopped(approxi- effective as those in breast milk. mately 3 minutes)has been shown to improve infants' iron status during the first 6 months of life (6,7). Carbohydrates Anti-infective factors The main carbohydrate is the special milk sugar lac- tose,a disaccharide.Breast milk contains about 7g Breast milk contains many factors that help to protect lactose per 100 ml,which is more than in most other an infant against infection(8)including: milks,and is another important source of energy immunoglobulin,principally secretory immuno- Another kind of carbohydrate present in breast milk globulin A(slgA),which coats the intestinal mucosa is oligosaccharides,or sugar chains,which provide and prevents bacteria from entering the cells; important protection against infection(4). white blood cells which can kill micro-organisms; Protein whey proteins (lysozyme and lactoferrin)which Breast milk protein differs in both quantity and qual- can kill bacteria,viruses and fungi; ity from animal milks,and it contains a balance of oligosacccharides which prevent bacteria from amino acids which makes it much more suitable for attaching to mucosal surfaces.The physiological basis of breastfeeding 2.1 Breast-milk composition Breast milk contains all the nutrients that an infant needs in the first 6 months of life, including fat, car￾bohydrates, proteins, vitamins, minerals and water (1,2,3,4). It is easily digested and efficiently used. Breast milk also contains bioactive factors that aug￾ment the infant’s immature immune system, provid￾ing protection against infection, and other factors that help digestion and absorption of nutrients. Fats Breast milk contains about 3.5 g of fat per 100 ml of milk, which provides about one half of the energy content of the milk. The fat is secreted in small drop￾lets, and the amount increases as the feed progresses. As a result, the hindmilk secreted towards the end of a feed is rich in fat and looks creamy white, while the foremilk at the beginning of a feed contains less fat and looks somewhat bluish-grey in colour. Breast-milk fat contains long chain polyunsaturated fatty acids (docosahexaenoic acid or DHA, and arachidonic acid or ARA) that are not available in other milks. These fatty acids are important for the neurological devel￾opment of a child. DHA and ARA are added to some varieties of infant formula, but this does not confer any advantage over breast milk, and may not be as effective as those in breast milk. Carbohydrates The main carbohydrate is the special milk sugar lac￾tose, a disaccharide. Breast milk contains about 7 g lactose per 100 ml, which is more than in most other milks, and is another important source of energy. Another kind of carbohydrate present in breast milk is oligosaccharides, or sugar chains, which provide important protection against infection (4). Protein Breast milk protein differs in both quantity and qual￾ity from animal milks, and it contains a balance of amino acids which makes it much more suitable for a baby. The concentration of protein in breast milk (0.9 g per 100 ml) is lower than in animal milks. The much higher protein in animal milks can overload the infant’s immature kidneys with waste nitrogen products. Breast milk contains less of the protein casein, and this casein in breast milk has a different molecular structure. It forms much softer, more eas￾ily-digested curds than that in other milks. Among the whey, or soluble proteins, human milk contains more alpha-lactalbumin; cow milk contains beta￾lactoglobulin, which is absent from human milk and to which infants can become intolerant (4). Vitamins and minerals Breast milk normally contains sufficient vitamins for an infant, unless the mother herself is deficient (5). The exception is vitamin D. The infant needs expo￾sure to sunlight to generate endogenous vitamin D – or, if this is not possible, a supplement. The minerals iron and zinc are present in relatively low concentra￾tion, but their bioavailability and absorption is high. Provided that maternal iron status is adequate, term infants are born with a store of iron to supply their needs; only infants born with low birth weight may need supplements before 6 months. Delaying clamp￾ing of the cord until pulsations have stopped (approxi￾mately 3 minutes) has been shown to improve infants’ iron status during the first 6 months of life (6,7). Anti-infective factors Breast milk contains many factors that help to protect an infant against infection (8) including: K immunoglobulin, principally secretory immuno￾globulin A (sIgA), which coats the intestinal mucosa and prevents bacteria from entering the cells; K white blood cells which can kill micro-organisms; K whey proteins (lysozyme and lactoferrin) which can kill bacteria, viruses and fungi; K oligosacccharides which prevent bacteria from attaching to mucosal surfaces. Session 2