Biochemistry of human Milk – Flashcards
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Colostrum - specific gravity
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1.04 - 1.06
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Mean energy value of colostrum
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67Kcal/100ml
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Mean energy value of mature milk
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75kcal/100ml
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Ph of milk
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7.45 initial then 7 in second week gradually rising to 7.4 by 10 months. (almost neutral)
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What causes colour of colostrum
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B - carotene - antioxident and nutrient
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What contents are higher in colostrum than mature milk?
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Ash content, Na, K, Cl, zinc, protein, fat -soluble vits. (Vit A, carotenooids and vit E v. high) and minerals, immunoglobulins (esp. IgA). Cholesterol is also present.
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What contents are lower in colostrum than mature milk?
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Fat (2-3gm/100ml in colostrums and 4-5gm/100ml in mature milk) , water soluble vits. and lactose content lower in colostrum than mature milk
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Function of colostrum
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Facilitates the establishment of bifidus flora in the digestive tract - coats gut to prevent adherence of pathogens Facilitates the passage of meconium Its low volume reduces metabolic stress on immature infant kidneys It has a low lactose content because production of lactase and other gut enzymes are just beginning. High antibodies protects against bacteria and viruses after the birth Contains antioxidants which may function as traps for neutrophils - generated reactive O2 metabolites. and protect against hemorrhagic disease.
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Transitional milk
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7 to 10 days postpartum to 2 weeks postpartum. Concentration of immunoglobulins, total protein, fat soluble vits decrease while lactose, fat, water soluble vits. and total caloric content increase. Volume: by day 5 volume is around 500mls/ day and it increases to about 800mls/day at month 6 of full breastfeeding. (range of 550-1150mls)
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Water in mature milk
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Constituent in largest quantity All other constituents are dissolved , dispersed or suspended in H2O Lactating women have a greatly increased obligatory uptake of water
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Second greatest constituent in human milk.
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Lipids - Fats are 4% by volume in mature milk,
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Predominant lipid in human milk
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triglycerides
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Function of lipids in human milk
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Maximum intestinal absorption of fatty acids Contributes to about 50% of calories. (Provides the major fraction of kilocalories in human milk. Provide cholesterol. Provide essential fatty acids (EFAs) and PUFAs
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Variation in lipids (most variable constituent)
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increased late morning and early pm. Hindmilk fat content 4 - 5 x greater than foremilk. Increases more steeply the more milk is taken.
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Fats-Effect of maternal diet and bm lipids
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effects the constituents of the lipids but not the total amount of fat Diets free from added fats or linoleic acid induce deficiency in infants. S/S skin lesions, decrease wt. gain and poor healing Vegetarians - higher progortion of polyunsaturated fats.
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Fats - cholesterol
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higher in bf babies but overall reduction in artherosclerosis important consituent of brain tissue - myelin sheath.
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Fats - Linoleic acid
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a polyunsaturated fat whose metabolites are very important in myelin formation and therefore brain and CNS development. MS is reduced in BF babies
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Fats - LC-PUFAs (long chain polyunsaturated fatty acids) include docosahexanoic acid (DHA) and arachidonic acid (AA)
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Thought to cause higher visual acuity and cognitive ability of the child.
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function Free Fatty acids (formed when Long Chain fatty acids (triglycerides) are broken down by lipase)
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kill bacteria and parasites and inactivate viruses.
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Protein in HM
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Constitute 0.9% of contents of human milk - 1.13 -2.07 /100mls, HM has the lowest protein content among mammals. The low protein result in a low solute load for the infants immature kidneys
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Differences in pariety and human mlk
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Primips have higher fat
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Protein - Casein
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Human milk forms a flocculent suspension with 0 curd tension. Curds are easily digested due to a high whey : casein ratio. This reduces gastric emptying time. The average gastric half emptying time for bm is 48mins and 78mins for AF The concentration of whey protein decreased from early lactation and casein ratios increase
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Protein -phenylalanine and tyrosine
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lower in hm than cm
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Protein -Taurine
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high in hm Necessary for conjugation of bile salts, develops brain and retina. Not in bovine milk
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Whey : Casein ratios
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Human: 80:20 (early lactation 90: 10, 60:40 mature milk and 50:50 late lactation) , bovine: 20:80, AF: 60:40
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whey proteins - alpha lactalbumin
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Function: regulates milk synthesis, mucins bind pathogens, kill cancer cells invitro (There is no measurable Beta lactalbumin which is the main component in cow's milk.)
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Giving iron to BF infants does what?
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appears to inactivate the lactoferrin by saturation it with FE.
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main immunoglobulin in breast milk?
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IgA (very stable at low pH and resistant therefore to proteolytic enzymes. Present in the intestine of BF babies and provides a defence against bacteria and viruses by stopping mucosal invasion.)
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Proteins: Lysozyme
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High concentration in HM Nonspecific antimicrobial factor - kill bacteria by disrupting cell walls. Bacteriolytic against Enterobacteriaceae and gram pos bacteria Contributes to dev. and maintenance of specific intestinal flora of BF infant 3000 x greater than in bovine milk
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NonProteins Nitrogen: Polyamines
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Increase the rate of transcription, translation and amino acid activation. Suggest a protective effect against alimentary allergies
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NonProteins Nitrogen: Nucleotides
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help in protein synthesis. May explain the satisfactory growth pattern of breastfed infants on relatively low protein intake and the more efficient protein utilization of breastfed infants. Recognised as an integral part of the immunosystem acting on the host defences against bacteria and viruses and parasites as well as various malignancies.
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NonProtein Nitrogen - Carnitine
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Increased in HM, important in brain lipid synthesis
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Protein - Taurine
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Abundant amino acid; associated with early brain maturation and retinal development.
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Predominant CHO
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lactose - disaccharide (galactose - CNS development + glucose - energy) 40% of energy needs only found in milk, highesst in HM, sweetest milk synthesised by the mammary gland from lactogenesis 2 increased greatly from day 4
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What enzyme hydrolyzesis lactose?
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lactase - in the tip of the intestinal villi
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Changes in lactose
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Constant throughout the day but effected by maternal diet
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Carbohydrates - Lactose functions
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Energy, enhances Ca absorption, critical in prevention of rickets, facilitates FE absorption protects GI from pathogens Supports CNS and cognitive development - increased lactose content in milk corresponds to an increased brain size
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Other charbohydrates in HM other than bifidus factor and oligosaccharides
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glycopeptides, fructose, galactose
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When are minerals highest in HM?
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first few days after birth and decrease slightly in a consistent pattern throughout lactation with little diurnal or within-feeding variation. (except Mg). Levels are not effected by mat. diet (even with supps.), pariety, age Na and Cl increased with masitits
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Major cations
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Na, K, Ca, MG
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Major anions?
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Phos, Cl, Citrate
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How much higher are Na levels in CM than HM?
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3.6 times
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Ca/Phos ratio is higher or lower in CM
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Lower but it is more efficiently absorbed and no rickets seen
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Why is Fe in HM more bioavailable than in CM?
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1. increase in GI acidity, 2. Appropriate levels of zinc and CU., 3. Transfer factor: lactoferrin which prevents bacteria in GIT using Fe 4. high levels of lactose and vit C in hm which promote absorption.
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Function of Zinc in HM
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As part of enzyme structure and as an enzyme activator. Def. S/S failure to thrive, persistant perioral or perianal rash.
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Role of fluorine in HM?
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Prevention of dental caries
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Vitamin levels over course of lactation
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the level of water-soluble vitamins in breastmilk increases, and the level of fat soluble vitamins declines.
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Which vitamins are minimally influenced by recent maternal diet )can be drawn from storage in the body.
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A, D, E, K
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Vitamins in greatest quantities
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A, C, E
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Vitamin A
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Twice as much in colostrum. Is very high in prem milk. Required for vision
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Vitamin d
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Increases with mothers taking supps and sunshine. Some cases of def. esp in cool climates with little sunshine
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Vitamin E
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Needed for muscle integrity, resistance of erythrocytes to haemolysis. May need supps for prems.
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Vit K
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Essential for synthesis of blood clotting factors which are normal in the serum at birth. Produced by intestinal flora but takes several days in the previously sterile gut to be effective. All infants receive Vit K injection at birth regardless of feeding plans.
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Vitamin C
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Essential to collagen synthesis. HM is outstanding source of water soluble vits. and reflect increased maternal uptake
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B1/ Thiamine
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Increased with duration of breastfeeding but lower in HM than CM. Essential for fat synthesis and carbohydrate metabolism.
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B2 / riboflavin
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Essential for protoplasmic growth Increased with supps. reduced in HM but it's bioavailibility is enhanced by a specific transfer factor.
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Niacin
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Increased in BM. Responds to supps
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Folic Acid/Folacin
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Essential for erythropoiesis, levels increase as lactation increases. Increased with supps
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B12
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Low in BM but has a high binding capacity
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Whey proteins - Enzymes in human milk
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Fnx: digestion of nutrients in milk, stimulate neonatal growth Amylase (high in colostrum, digests polysaccharides, BF infants have few problems digesting starch) Lipase (Pancreatic lipase is immature so HM contains it's own, HM fat is almost completely digestible, makes free fatty acids available in large portions, distroyed by heating, FFAs inactivate bacteria and parasites eg. protozoa , giardia, entamoebas) Diastase, Lysozyme- attacks cell walls Protease (high in BM) Alkaline phosphatase Peroxidases act like hydrogen peroxide and oxidize bacteria (Xanthine oxidase, Sulfhydryl oxidase, Glutathione peroxidase)
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Growth Factors
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Epidermal Growth Factor - aid gut and other tissue maturity Nerve growth factor - help CNS Insulin like growth factor
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Anti-inflammatory factors
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Prostoglandins (GI motility), Cytokines (activate immune system), Epidermal Growth Factor (promote gut maturation and epithelial cell growth)
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Role of relaxin in HM
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Acts on GI tract
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Cells in HM
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Phagocytes / macrophages - engulf and absorb pathogens; release IgA Lymphocytes - T and B cells - cell mediated immunity
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changes in milk over time
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increased fat and energy, serotonin and lysozymes zinc decreases as volume drops protective factors increase in proportion to total volume. whey - casein ratio Ca decreases
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Colostrum volumes
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D1: 37mls - stomach volume 7mls D3: 408mls - stomach capacity 27mls D5: 705mls - stommach capacity 57mls
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Whey proteins - lactoferrin
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Function: competes with bacteria to bind iron, iron transport and absorption, antibacterial, essential growth factor for B and T lynphocytes, promotes growth of lactobacilli, prevents inflammation including NEC Produced in mammary epithelial cells, milk ducts and toher regions of the body.
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Whey Proteins - secreory immunoglobulin A (SIgA)
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Coats mucosal surfaces to prevent adherence and penetration by pathogens Also IgG, IgM and IgM
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Whey Protein - Hormones and hormone-like substances
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insulin Prostoglandins Oxytocin relaxin thyroid hormones - thyroxine/TRH/TSH- (prevents hypothyroidism; cholecystokinin (CCK) - enhances digestion, produces a sleepy feeling in both mother and infant. Prolactin (different from mother's serum prolactin) enhances development of B and T lymphocytes), oestrogens, thyroid releasing hormone and thyroid stimulating hormone (protect infants from hypothyroid states, stimulates infants intestine) , androgens, cortisol (role not clear) Beta endorphins - higher in the colostrums of women who delivered prematurely, vaginally, and without epidural analgesia. Help babies overcome birth stress.
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Other carbohydrates in HM - Oligosaccharides
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stim. growth of bifidum flora, block pathogens from attaching to gut, protect against enterotoxins
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Other carbohydrates in HM - Bifidus Factor
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combines with lactose, promotes growth of lactobacillus factor which occupies the intestines , crowds out pathogens and produces an acid detrimental to pathogen growth. Contributes unique aromoa of exclusively bm stool.
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Fats: Ratio of saturated to unsaturated fats
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42% saturated: 57% unsaturated.
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Cells in HM
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Macrophages - 90% of cells in HM contain IgA, phagocytosis, make/facilitate lactoferrin Leukocytes Lymphocytes - tcells and B Cells Epithelial celss Neutorphil granulocytes
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Fe in HM
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50% of iron absorbed from bm compared to 7% from AF Full term babies have sufficient stores until 6mths
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Preterm milk
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higher protein, Na, cl than mature lower lactose
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Human milk genetic specifity
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HM matches more than 50% of baby's genetic material
