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By Emma Turner ND
Nutritional Advantages of Breast-feeding
One of the major benefits of breast milk compared to formula milk is its nutritional content. It contains an optimal amount of fatty acids, lactose, amino acids for human digestion, brain development and growth5. The composition of human breast milk varies at different times of the day and from one period of lactation to another2. Rates of growth and activity in mammals tend to be related to the need for protein in the breast milk. One of the slowest rates of mammalian growth is seen in humans, thus human milk contains one of the lowest amounts of protein2.
The main proteins in human milk are2:
1. Casein (40%)
2. alpha-Lactalbumin (60%)
3. Lactoferrin
4. Secretory IgA (whey proteins)
5. Serum albumin
6. Immunoglobulins
7. Glycoproteins
In human milk the amino acid content is recognised as ideal for the human infant with low levels of some amino acids (methionine and phenylalanine) deemed to be detrimental in high levels, and high in some amino acids that infants rely on and cannot synthesize such as cystine and taurine 2, 14.
The majority of lipid in human milk (90%) is in the form of triglycerides and the remainder is composed of phospholipids, diglycerides, monoglycerides, glycolipids, sterol esters, free fatty acids and cholesterol. The levels of linoleic acid and oleic acid are greater in human milk than in cow's milk, while levels of short chain saturated fatty acids are greater in cow's milk. Cholesterol, needed for rapid growth of the myelin sheath in the central nervous system, is present in higher levels in breast milk than formula milk. The presence of cholesterol in breast milk also stimulates the development of enzymes needed for cholesterol degradation later in life2.
Human milk provides infants with polyunsaturated fatty acids (PUFAs), including docosahexaenoic acid (DHA) and arachidonic acid (AA), while many formula milks, if fortified with long chain polyunsaturated fatty acids, only contains the precursors alpha linolenic acid (ALA) and linoleic acid (LA). Formula fed infants are therefore left to synthesise DHA and AA. As both ALA and LA compete for the same enzyme pathways for this conversion, it may be impaired in infants fed formula milk. This is evidenced further by lower levels of plasma and erythrocyte DHA and AA in formula fed infants compared to breastfed infants.
It has also been suggested that the PUFA profile in blood may be a representation of what is present in neural tissue, and the percentage of DHA in the brain cortex of breastfed infants has been shown to be greater than in those infants fed formula milk6.
Immune Benefits to the Infant
Breast milk confers passive immunity to the infant from the mother. In the mother's body migrating B cells, with the role of developing antibodies7, are taken up by Peyer's Patches (lymph nodes in the gut mucosa) and travel to the mammary glands, in addition to various exocrine glands and mucosal membranes. After binding to the receptors in the mammary gland antibodies produced by B cells are transported through the glandular epithelium and into the milk8.
Secretory IgA is the principal immunoglobulin in exocrine secretions such as milk. It plays an important part in protecting the infant's mucus membranes from pathogenic bacteria and viruses9. Secretory IgA's production is initiated by hormones involved in inducing lactation. It is produced by plasma cells10 (mature B-lymphocytes7) in the mammary glands which direct their defences against bacteria, viruses and other antigenic substances that the mother has been recently exposed to, thus providing this protection to the infant via the breast-milk10. Colostrum's main protein is secretory IgA, and later in the breast-feeding process lactoferrin becomes the main protein in the mature milk. Lactoferrin is anti-inflammatory and has anti-bacterial, anti-viral and anti-fungal properties, as well as killing some tumour cells10.
Human milk also contains cytokines that may contribute to the maturation of the intestines and oligosaccharides which prevent the binding and adherence of certain microbes and their toxins to intestinal epithelial cells which cause diarrhoea and gastric irritation10, 15.
Additional Benefits of Breast-feeding:
As well as nutritional benefits, human breast-feeding also provides a number of other benefits5:
1. Proper jaw development is promoted by the stronger sucking action required to create milk flow from the breast. This exercises and strengthens the jaw, promoting the growth of straight healthy teeth.
2. Human milk is normally sterile, reducing the risk of infection from contaminated milk.
3. The psychological benefits - the bonding time of mother and child. Studies have shown that infants at one week of age prefer the smell of their own mother's breast-milk. (Breast pads were soaked with breast-milk in babies' cribs and their faces turn toward the one that smells familiar).
Benefits of Breast-feeding to Mothers
While there are many benefits to breastfed infants, there are also benefits to mothers. Some of these are5 :
1. The stimulation of the uterus to contract back to its original size and tone
2. Breast-feeding also requires extra calories and this increased demand for energy can assist the mother in shedding any weight gain associated with the pregnancy
3. Convenience - having ready-made milk on demand makes for easy, regular feeding which facilitates resting for the mother
4. Helps to act as a contraceptive, as breast-feeding suppresses ovulation. However, this is not a reliable form of contraception on its own
5. Formula milk can be expensive and breast milk is ready when required with little or no equipment.
While breast milk is a naturally made food source for infants, it can also be recommended to assist in preventing certain health problems. Exclusive breast-feeding has been shown to decrease the risk of dying from respiratory infections by 3.6 times compared to formula or cow's milk feeding. Post weaning, breastfed infants also have reduced risk of death from other infections10.
In a large study it was found that each additional month of breast-feeding decreased infant mortality by 6.2 deaths per 1000. In comparison, artificial feeding increased neonatal and postnatal mortality by a factor of 1.8 to 2.6 per 100010.
Moreover, breast milk contains heat stable growth promoting factors that may promote repair of damaged intestinal mucosal cells. Eleven infants diagnosed with severe protracted diarrhoea lasting one to 14 months despite dietary and other treatments, were given human breast milk. In all instances, diarrhoea resolved and weight loss stopped within seven days of the introduction of the human milk feeds12.
Development of Allergies
An association has been found between the diversity of the infants' diet during their first month and development of eczema. Delayed introduction of a single food allergen is shown to postpone single-food allergy. Prolonged breast-feeding has been shown to have prophylactic properties against atopic disease for up to three years of age11.
Prophylaxis of atopic disease in infants with hereditary risk has long been an area of interest for researchers. After six months of age the danger of developing new allergies can be largely reduced if breast-feeding is maintained8and while maternal elimination diet during late pregnancy did not protect against atopy, elimination diet during lactation did reduce infantile eczema in high-risk individuals11.
It seems that the more IgA the mother has in her breast milk against cow's milk proteins, the less risk of developing cow's milk allergy her children will have10. It has therefore been suggested that breast-feeding may enhance the development of immunological tolerance against food that should normally appear early in life10.
The Role of Probiotics
In a study on atopic eczema, probiotics were shown to provide protection to infants when given to the mother before delivery and during breast-feeding13. Elevated core blood IgE is used as a marker to reflect atopic sensitization in utero. Infants with this marker were the most likely to benefit from probiotics, which were shown to increase the amount of TGF-?2 (transforming growth factor) in breast milk. TGF-?2 is a major immuno-regulatory factor in promoting IgA production and induces oral tolerance. Its concentration correlates with the infants production of specific IgA antibodies against dietary antigens13.
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