Female milk is a nutrient fluid produced by a woman’s mammary glands . It changes its composition both at the stages of pregnancy - childbirth - breastfeeding - colostrum - transitional - mature milk, and during each feeding - front - back milk. In its composition, it meets the nutritional requirements of the child during infancy, and also performs the functions of immune defense and regulation of the growth of the child .
| Female milk Nutrition value per 100 g of product | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Energy value 70 kcal 291 kJ | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Source: USDA Nutrient database | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Content
- 1 Composition
- 1.1 Proteins
- 1.2 Fats
- 1.3 Carbohydrates
- 1.4 Enzymes
- 1.5 Immune factors
- 1.6 Hormones and growth factors
- 2 Properties
- 3 See also
- 4 notes
- 5 Literature
Composition
- Solids - 11.9%
- Fat - 3.9%
- Protein - 1.0% (including casein - 0.4%)
- Lactose - 6.8%
- Minerals - 0.2%
The composition of breast milk during lactation varies depending on the lactation period, time of day, and even from the beginning to the end of each feeding. The content of some components, for example, water-soluble vitamins (ascorbic, nicotinic acids, thiamine, riboflavin, pyridoxine) to a certain extent depends on the diet of the mother. The content of other components, for example, iron, does not depend on the mother’s diet [1] .
Squirrels
The total amount of protein in human milk is 0.9-1.0%, which is 2-3 times lower than in cow's milk. Casein content is low at the beginning of lactation (whey protein / casein ratio 90:10); in mature milk, the proportion of casein is higher (whey protein / casein ratio 60:40) [2] . The size of casein micelles is 42 nm.
The complex of partially expanded alpha-lactalbumin (whey protein of breast milk) and oleic acid , called HAMLET (abbreviation for Human Alpha-Lactalbumin Made Lethal to Tumor Cells), causes programmed death ( apoptosis ) of tumor cells both in vitro and in vivo [3 ] . The conditions necessary for the formation of the HAMLET complex are present in the baby’s stomach while breastfeeding: low pH can expand the protein molecule due to the release of calcium; hydrolysis of milk triglycerides with acid-sensitive lipases occurs with the release of oleic acid.
Fats
The fat content ranges from 2.1 to 5.3%, while the breast milk fat contains 1.5-2 times more unsaturated fatty acids (including essential ones ) compared to cow's milk fat. Milk fat is finely dispersed, which contributes to a better absorption of fat by the body of the child. The milk fat content is inversely proportional to the fullness of the breast: at the beginning of feeding, the baby receives the so-called front milk with low fat content. Such milk quenches the thirst of a child well. As the baby empties the breast, the concentration of fat in the milk gradually increases. The “back” milk that the baby receives at the end of feeding contains more fat.
A mother’s diet does not affect the total fat content in milk. But at the same time, the composition of fatty acids in milk depends on the type of fat in a woman’s diet.
Carbohydrates
Breast milk contains a lot of lactose - 6.8% and about 1% of other more complex oligosaccharides , which stimulate the development of bifidobacteria in the intestines of an infant.
Lactose is important for the absorption of calcium. The high content of lactose, which breaks down into glucose and galactose during the digestion of milk, provides energy to the rapidly growing brain of the child.
About 130 varieties of oligosaccharides have been found in breast milk. Oligosaccharides can block antigens and prevent their attachment to epithelial cells. For example, this mechanism blocks the adhesion of pneumococcus .
The oligosaccharide is also the bifidus factor contained in breast milk, which stimulates the growth of bifidobacteria in the intestines of the baby.
Enzymes
Breast milk contains active hydrolytic enzymes: lipase , amylase , protease , xanthine oxidase [4] and is characterized by less active peroxidase and alkaline phosphatase .
The lipase activated by the bile salts, produced by the mother’s mammary gland and ingested into the baby’s body with human milk, compensates for the low amount of the newborn’s own enzymes and helps the child absorb fats. Free fatty acids , which are formed during the breakdown of fats in the baby’s gastrointestinal tract by human milk lipase, have a strong antiviral and antiprotozoal effect. Activated by bile salts, lipase is the main factor inactivating pathogenic protozoa .
Immune factors
Breast milk contains a wide range of immunological defense factors.
The main types of immune cells found in human milk are phagocytes (mainly macrophages ) (90% of the cell population), T-lymphocytes and B-lymphocytes (10% of the breast milk cell population). These cells remain active in the baby’s gastrointestinal tract.
The main class of human milk immunoglobulins is secretory immunoglobulin A (sIgA). This immunoglobulin protects the mucous membranes of the child - the main gateway to infection for children of this age. In colostrum , sIgA content reaches 5 g / L, in mature milk - up to 1 g / L. Secretory immunoglobulin A is resistant to low pH and proteolytic enzymes and remains active in the baby's digestive tract, covering its walls with a protective layer. Despite the fact that the concentration of immunoglobulins A in mature milk is lower, the child receives enough of these antibodies due to the fact that it absorbs a larger volume of milk. It was estimated that during the entire period of breastfeeding, the baby receives approximately 0.5 g of secretory immunoglobulin A per day. This is fifty times more than the daily dose of IgA received by patients with hypoglobulinemia [5] .
The immunoglobulins that are delivered with breast milk to the baby are specific for the baby’s pathogens. This is because every time a mother makes contact with her baby - breastfeeds, wears on her hands, kisses, sniffs, touches the baby, changes diapers, bathes him - she inhales and / or swallows bacteria and other pathogenic microorganisms (which are on the skin) child, in feces, etc.). These pathogens activate B-lymphocytes , which are located in the lymph nodes of the intestinal-associated and bronchial-associated lymphoid tissue of the mother. Some of these activated lymphocytes migrate into the mammary gland and produce secretory immunoglobulin A, which passes through breast milk to the baby. Thus, with each application to the breast, the baby receives antibodies specific to those pathogens that he and his mother are exposed to [1] .
Broad spectrum antimicrobial protection is provided by lysozyme and lactoferrin enzymes. Lactoferrin makes up from 10% to 15% of the whole protein component of human milk.
In the second year of lactation, the concentrations of lysozyme, lactoferrin, total and secretory immunoglobulin A are higher than in the first year of lactation.
About 600 (according to other sources, more than 700 [6] ) species of bacteria are found in human milk. Among them, bifidobacteria of several species (B. breve, B. adolescentis, B. longum, B. bifidum, B. dentium). [7] . In addition, the milk contains complex long chain sugars , the so-called oligosaccharides . There are about ten grams of them in a liter of breast milk, which is 10-100 times more than in the milk of any other mammals . Oligosaccharides are not intended for the nutrition of the child himself, since the latter lacks the necessary enzymes for this, but for the nutrition of bifidobacteria, which are found in breast milk [6] .
Hormones and growth factors
Breast milk contains epidermal growth factor, nerve growth factor , human growth factors I, II and III, insulin-like growth factor , erythropoietin , thyroxine and thyrotropin-releasing hormone , cholecystokinin , beta- endorphins , prostaglandins , prolactin , leptin , ghrelin , adiponectin , resistin obestatin [8] .
Properties
Breast milk has the following physicochemical and technological properties:
- acidity = 3 ÷ 6 ° T, pH = 6.8 ÷ 7.4
- density = 1026 ÷ 1036 kg / m³
- high thermal stability (more than 50 minutes at 130 ° C), due to the low content of ionized calcium.
Special adapted milk mixtures are produced for the artificial feeding of infants who for some reason do not receive breast milk. Methods for adapting cow’s milk mixtures are reduced in the amount of proteins , in balancing essential acids, polyunsaturated fatty acids, minerals (Ca, P, Na), vitamins, and increasing the lactose content. Nevertheless, all the mixtures contain only a part of the composition of substances desired for the infant to receive, and correspond only to the minimum requirements for adaptation to human milk. In the mixtures there are no immune factors, hormones and growth factors. Children who are raised on artificial feeding have poorer intelligence, immunity, and general health than breast-fed children.
According to a study at University College Dublin , breastfeeding does not affect the cognitive abilities of the child, but reduces the level of hyperactivity [9] .
See also
- Breast-feeding
- Milk
- Breast milk substitute
Notes
- ↑ 1 2 Riordan J. Breastfeeding and Human Lactation . Jones and Bartlett Publishers, 2004.
- ↑ Kunz C., Lönnerdal B. Re-evaluation of the whey protein / casein ratio of human milk (Eng.) // Acta Paediatr : journal. - 1992 .-- February ( vol. 81 , no. 2 ). - P. 107-112 . - PMID 1515752 .
- ↑ Gustafsson L., Hallgren O., Mossberg AK, Pettersson J., Fischer W., Aronsson A., Svanborg C. HAMLET kills tumor cells by apoptosis: structure, cellular mechanisms, and therapy. (Eng.) // J Nutr : journal. - 2005 .-- May ( vol. 135 , no. 5 ). - P. 1299-1303 . - PMID 15867328 .
- ↑ Stevens CR Antibacterial properties of xanthine oxidase in human milk // The Lancet : journal. - Elsevier , 2000 .-- September ( vol. 356 , no. 9232 ). - P. 829-830 . - PMID 11022933 .
- ↑ J. Acre. Feeding children in their first year of life: physiological basis: adj. to that 67, 1989 Bulletin World. org health care . - Geneva: WHO, 1991.- 120 p.
- ↑ 1 2 Taylor, 2016 , p. 37.
- ↑ Martin, R; Jiménez E., Heilig H., Fernández L., Marín M., Zoetendal E., Rodríguez J. Isolation of Bifidobacteria from Breast Milk and Assessment of the Bifidobacterial Population by PCR-Denominating Gradient Gel Electrophoresis and Quantitative Real-Time PCR. (English) // Applied and Enviromental Microbiology: journal. - 2009. - Vol. 75 . - P. 965-969 . - DOI : 10.1128 / AEM.02063-08 . - PMID 19088308 .
- ↑ Francesco Savino, Stefania A. Liguori, Maria F. Fissore, and Roberto Oggero. Breast Milk Hormones and Their Protective Effect on Obesity // International Journal of Pediatric Endocrinology: journal. - 2009. - Vol. 2009 . - P. 8 . - PMID 20049153 .
- ↑ Breastfeeding does NOT boost a baby's IQ: Nourishing infants the natural way only makes them less hyper
Literature
- Obgolts A.A. Microbiology and immunology of breast milk. - Omsk, 2000 .-- 107 s.
- Jeremy Taylor Darwin Health: Why We Get Ill and How It Tells Evolution = Jeremy Taylor “Body by Darwin: How Evolution Shapes Our Health and Transforms Medicine”. - M .: Alpina Publisher, 2016 .-- 333 p. - ISBN 978-5-9614-5881-7 .
- Lukoyanova O. L. Breast milk as a reference model for the creation of infant formula. Scientific Center for Children's Health RAMS, Moscow, 2012.
- The Importance of Breast Milk for Infant Immunity. (unavailable link) Per. from English N. D. Firsova (2017).