Introduction to Lactation and Protein Comp
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What happens to a woman's hormones after giving birth?
- Significant drop in progesterone and estrogen
- Hormonal cascade initiates secretion of milk
What 2 things are involved in stimulating milk production?
- Nerves and hormones
- Nipples send signals to hypothalamus and pituitary gland via spinal cord
- Prolactin stimulates milk production and oxytocin stimulates milk release
Why is a womans support system crucial after giving birth?
Psychological issues can cause decreased milk flow
What can cause insufficient milk production?
Poor suckling response in LBW (neurologically impaired infants)
What is done to counteract the effects of insufficient milk production and release?
Milk polypropylene tube feeding at same time as breast-feeding
What cells produce milk?
Alveolar cells in mammary glands produce milk- stimulated by prolactin from the anterior pituitary
What cells release milk?
- Myoepithelial cells from mammary glands contract--> milk movement through duct system for release 'let-down'
- Stimulated by oxytocin (posterior pituitary)
What is oxytocin?
- 'mothering' response in mammals- increase in maternal-child bonding
- 'Satisfaction or pleasure' hormone
- Stimulates contraction (involution) of the uterus to help control blood loss
What suppresses ovulation?
Decrease in estrogen and progesterone and an increase in prolactin
What are the advantages of breastfeeding?
- May aid in proper jaw and tooth development
- Bacteriologically safe and always fresh
- Contains a variety of anti-infectious agents and immune cells
- Breast milk is nutritionally superior
- Associated with a decreased risk of food allergy
What is a problem with bottle feeding in developing countries?
Increased risk of infection, especially in developing countries with contaminated water supplies
What is problem is associated with formula feeding?
Increased risk of food allergy
What are the compartments of milk?
Micelles. membrane-bound globules, live cells, protein and non-protein nitrogenous compounds, CHO, lipids, vitamins, minerals and trace elements
What are the 3 sources of milk components?
- Transfertred from maternal plasma
- Synthesized from maternal secretory (alveolar) cells from maternal plasma precursors
- Synthesized from other mammary cells in situ
What factors can affect milk composition?
Hormones, other maternal physiological changes and diet
What is colostrum?
- First 5-7 days of milk production
- Relative to mature milk, has: increased protein and mineral content (Na, K, Cl)
- Decreased energy, fat and lactose content
- Intense transparent yellow fluid
- Color due to carotenoid content (10x higher than mature milk)
- Only 2-10mL feeding/day
What are the 3 stages of milk production?
- Transitional Milk
- Mature Milk
What is transitional milk?
- 7 days to 3-4 weeks
- Protein content drops to consistent level with increases in lactose and fat
- Continues from colostrum stage until 30th day of lactation
What is mature milk?
Changes according to the changing infant's needs
What are the immunological properties of human breast milk?
- Direct action against pathogens
- Modulation of immune response
- Promotion of growth and maturation of GI tract
What are the anti-infectious agents in human breast milk?
- Immunological factors produced throughout lactation, nut some factors are highest in colostrum
- Most immune factors not found in formula and lower concentrations in cow's milk
What is the importance of whey proteins in breast milk?
- Many whey proteins have immunological enhancing properties
- Lactoferrin (bacteriostatic, iron-binding)
- Resistant against proteolysis/acid via anti-proteases which protect proteins by preserving their disulfide bonds
Why are anti-proteases important in breast milk?
Preserve their S-S bonds which maintain protein conformation and activity
What is the importance of anti-bodies in breast milk?
- Directed against specific bacteria, bacterial toxins, viruses, fungi and food proteins (which may cause allergy)
- Important as infants immune system takes several months to mature fully
What is the importance of IgA, IgM, IgE, IgI in human breast milk?
- Produced locally from mammary gland
- IgG absorbed from maternal plasma
- Act against bacterial invasion of the mucosa
- Inhibit colonization of the gut via their bacterial and viral neutralizing capacities
What is IgA?
- 90% of the secretory Igs
- Originates from the B cells from the maternal small intestine or respiratory tract and enter the maternal blood
- Lactogenic hormones stimulated B cells to travel to mammary gland
- Decreased byt significant concentrations in mature milk
- IgA acts on mucosal surfaces of GI tract and is resistant to proteolysis
Where to B cells originate from and how do they get into breast milk?
- B cells originate from maternal sites where pathogen exposure is high
- B cells travel to the mammary gland to form plasma cells producing IgA
What is the bifidus factor?
- N-containing CHO
- Promotes the growth of lactobacilli (bifidobacteria)
- Lactobacilli antagonize the survival of enterobacteria (diarheal diseases in childhood)
What is the importance of lactobacilli in babies?
- Lactobacilli antagonize the survival of enterobacteria (diarrheal diseases in childhood)
- Dominant bacteria of the lower GI of breast-fed infants
- Secrete organic acids such as acetic acid --> inhibit pathogenic bacterial overgrowth
What is necrotizing entercolitis?
infects and destroys intestinal tissue--> acute inflammation of intestinal mucosa
What is N-acetylglucosamine (gangliosides)?
Decreases risk of diarrheal diseases
What are lysozymes?
- High concentrations throughout lactation
- Break dwon susceptible bacteria by breaking down proteoglycans from cell wall
What is lactoferrin?
- Anti-infectious agent in milk
- Inhibits siderophilic (fe-absorbing) bacteria
- Competes for Fe as it is 80% in Apo form
- Produced by milk lymphocytes
What are lactoperoxidases in milk?
- Anti-infectious agents in milk
- Kills streptococci and enteric bacteria
Why are lipases important in breast milk?
Enhance fat breakdown in gut --> products of FFA and monoacylglycerols have antiviral properties
What is interferon?
- Anti-infectious agent in human breast milk
- Produced by milk lymphocytes and inhibits intracellular viral replication
What is the importance of B12-binding protein in human breast milk?
Renders vitamin B12 unavailable for bacterial growth
What is the importance of white blood cells in human breast milk?
- Neutrophils and macrophages = 90% of WBC (lymphocytes = 10%)
- neutrophils- intracellular phagocytosis
What is the importance of macrophages in human breast milk?
Activated when secreted--> antigen-processing properties for presentation to T lymphocytes (recognition of foreign material)
What is the importance of lymphocytes in human breast milk?
Synthesize secretory IgA and other Igs
What is the importance of fibronectin in human breast milk?
What is the importance of complement proteins in human breast milk?
- Promotes opsinization
- Rendering bacteria and other cells more susceptible to phagocytosis
What are some growth factors in human breast milk?
- Insuline-like Growth factor
- Vitamin E
What is the importance of cortison/thyroxine/insulin in human brease milk?
Stimulates synthesis of intestinal enzymes and maturation of gut mucosa
What is the importance of prostaglandins in human breast milk?
- Stimulates mucus secretion and cell division
- Important as mucosal barrier is immature in newborn
What is the importance of polyamines in human breast milk?
- Spermine and spermidine
- Growth factors, increase cell replication
What is the importance of vitamin E in human breast milk?
Stimulates immune system
What is the importance of insuline-like growth factor in human breast milk?
Increases rate of gut maturation
What are the 2 proteins found in milk?
Caseins and whey
What are caseins?
Complexes of caseinates found in micelles in combination with Ca, Mg, and phosphates
What is whey protein?
Thin liquid remaining after removal of the acid precipitate of the curd (casein) and removal of cream
What is directly affected by the protein content in different types of milk?
- Growth rates in animal species related to milk protein content
- Humans have one of the slowest growth rates and very low protein concentrations
What are the advantages of human milk vs bovine milk in terms of nutrient content?
- whey:casein ratio (60:40 in huma, 40:60 in cow)
- Higher proportion of nucleotides
- Better balance of essential amino acids
- Decreased risk of allergic reaction
Why is it important to have a higher whey content in baby milk?
- Softer, more easily digestible curd
- Better absorbability - in newborns, acidity and pepsin secretions are immature
Where is IgA produced?
Dimeric IgA: produced by plasma cells of mammary gland -> transported into milk
Why are whey proteins important in milk?
Major supplier of minerals
What are the major whey proteins in human milk?
Lactalbumin, IgA and serum albumin
What is b-lactoglobulin?
- 10% of cows milk
- Responsible for most of antigenicity of cows milk--> allergenic properties of cows milk
What are the major whey proteins in cows milk?
IgG, B-lactoglobulin, BSA
Why is bovine serum albumin not good for babies?
BSA different from HSA; implicated in the development of DM-1
How does BSA relate to diabetes?
Antibody for BSA is present in most type 1 diabetics but only in 2.5% of the non-diabetic population
What is colic?
- Inconsolable crying, abdominal distress and distension and excess gas, 1st 2-4 months and ends by 3-4 months
- 10-15% believed to be related to cows milk allergy
What is thought to cause colic in cows milk?
How is most nitrogen found in human milk?
- 15-25% of all nitrogen in human milk is in the form of nonprotein nitrogen (NPN)
- amino acids, peptides, -acetyl sugars, urea, nucleotides
What makes human milk more easily digestible?
High proportion of NPN to protein N in human milk --> better digestibility
How do NPNs help with GI maturation?
Polyamines, nucleotides (orotic acid) may play a role as growth factors in the human gut to aid GI maturation
Why is taurine content important in human milk?
- A principle component of NPN, 30x greater in human milk s cows milk
- Needed for bile acid conjugation; putative neurotransmitter and conditionally essential amino acid in infants
- Conditionally essential for new borns
What happens if infants are deficient in taurine?
TAU-deficient formula fed infante--> abnormal retinograms
Why are premature infants supplemented with taurine?
Increased maturation of responses (auditory, visual etc)
Why is a low cystein:methionine ratio in cows milk not good?
- Cystine ca be used without methionine metabolism
- Methionine metabolism is impaired (developmental delay in cystathionase)
- Use of cystine prevents methionine build up; most toxic amino acid
- May adversely affect CNS
Why are low phenylalamine and tyrosine in human milk important?
- Enzymatic delays in metabolizing
- Excessive PHE and excessive TY%R could be neurotoxic (more of a potential problem for premature infants)
- Tyrosine aminotransferase and para-hydrosyphenyl pyruvate oxidase are late to develop
- Excess blood PHE and TYR may adversely affect CNS
How often does cows milk allergy occur?
Occurs in about 1-7.5% of infants
What are the clinical signs of cows milk allergy?
- GI tract (vomiting, nausea)
- Respiratory (sneezing, wheezing, chronic cough)
- Skin (dermatitis)
- Neurologi8cal (headaches)
What causes a major reaction to cows milk?
- Interaction between IgE and food proteins--> complex
- Binds to Fc receptor on mast cells/basophils--> release of cytokines, interleukins and platelet activating factor
- Inflammatory response via increased histamine release; increased susceptibility to histamine release
- Histamins: bronchial hyperactivity, asthma, dermatitis, vomiting, diarrhea
How is cows milk allergy managed?
- Casein/whey protein hydrolysates
- Cross reactivity between milk and soy protein--> allergenic reactions to soy in addition to cows milk
How does breast milk protect agains milk allergy?
- IgA from human breast milk aids in the blockage of whole food proteins from absorption by binding them
- The IgA-food protein complex promotes mucus release from goblet cells and proteolysis at the mucosal surface
- Blood IgA binds to food proteins and clears them out via the reticuloendothelial system
- Infants have leaky junctions in GI tract--> antigens can pass through
- Colostrum hastens closure of leaky junctions
Why is soy milk formula not ideal for babies?
- Soy protein associated with poorer bioavailability of Zn, Ca, Fa (phytic acid-protein complexes)
- 25% more Ca and 50% more phosphorous, but a decrease in bone density because there is a decrease in calcium and phosphorous retention with soy formula feeding
What is Heiner's Syndrome?
- Hypersensitivity to cows milk protein in infants fed unheated cows milk
- Gi blood loss and Fe deficiency anemia
- Failure to thrive
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