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NUTR 2050 (77)
Chapter 6


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NUTR 2050
Jess Haines

CHAPTER 6: Nutrition during Lactation Key Nutrition Concepts • Human milk is the best food for newborn infants for the first year of their life or longer • Maternal diet doesn’t significantly alter protein, carbohydrate, fat, major mineral composition of breast milk BUT it dies alter fatty acid profile and the amount of vitamins and minerals • When maternal diet is inadequate the quality of milk is preserved over the quantity for the majority of nutrients • Health care policies/procedures and the knowledge and attitudes of health care providers affect community health Breastfeeding Goals For The USA • In early 1900s almost all infants were breastfed -introduction of human milk substitutes (HMS) • In 1950/60s breastfeeding reached levels below 30% -peaked in the 70s and 80s to above 60% in recognition of health and economic benefits of breastfeeding • Longer duration of breastfeeding is associated with higher education and socio economic status -also living in western USA , being older and married • Healthy People 2010 has objectives for national health goals 1. Increasing quality and yeas of healthy life 2. Eliminating racial and ethnic disparities in health 3. Increased emphasis on the duration of breastfeeding -increase proportion of mothers who exclusively breastfeed their infants through 3 months (60%) to 6 months (25%) • 77% of infants born in 2005/6 are reported to have been breastfed in the early postpartum period • American Academy of Pediatrics recommend babies be breastfed until 6 months, but rates are lower than 50% • Gaps in breastfeeding remain -geographically -among racial groups -educational groups -income groups -marital status • Highest rates of breastfeeding in western states -California, Washington, Oregon, Hawaii • Low rates for younger and unmarried women and women with low incomes LACTATION PHYSIOLOGY Functions of the Mammary Gland • Mammary gland is the source of milk for offspring called the breast -common characteristic of mammals • Alveoli: rounded/oblong shaped cavity present in the breast -composed of secretory cells: responsible for secreting milk components into ducts • Ducts are arranged like branches, each smaller ducts leading to 6 – 10 larger collecting ducts, these lead to the nipple • Myoepithelial cells: line the alveoli and can contract to cause milk to be secreted into the duct -contract under the influence of oxytocin: hormone produced during letdown Mammary Glad Development • Increase release of estrogen and progesterone by ovaries governs pubertal breast development • Mammary gland develops its lobular structure (lobes) through the cyclic production of progesterone and complete within 12-18 months after menarche -secretory cells develop, nipple grows, pigmentation changes, fibrous and fatty tissues increase • In pregnancy luteal and placental hormones (placental lactogent & chorionic gonadotropin) allow further preparation for breastfeeding • Estrogen stimulates development of gland that will secrete milk • Progesterone allows tubules to elongate and epithelial cells (that line tubules) to duplicate Lactogenesis • Breast milk production occurs in 3 stages • Stage 1 begins during the last trimester of pregnancy, stage 2 +3 occur after birth Lactogenesis 1 -milk begins to form, lactose and protein content of milk increases -this stage extends through the first few days postpartum Lactogenesis 2 -begins 2-5 days postpartum, increased blood flowing to the mammary gland -changes in milk composition and quantity of milk that can be produced over first 10 days of baby’s life Lactogenesis 3 -begins 2-10 days after birth -milk composition becomes stable Hormonal Control Of Lactation • Prolactin: hormone that stimulates milk production • Suckling is major stimulation for Prolactin secretion, levels double • Stress, sleep, sexual intercourse also stimulate prolactin levels • To prevent milk production in last 3 months of pregnancy, prolactin activity is suppressed by prolactin-inhibiting factor released by the hypothalamus • Actual level of prolactin in the blood is not related to the amount of milk made -prolactin is necessary for milk synthesis to occur • Oxytocin’s role is in the letdown/ejection of milk from the milk glands (acinus) -women can experience tingling/shooting pains that corresponds with contractions in the milk glands -oxytocin acts on the uterus, causes it to seal blood vessels and shrink in size Secretion of Milk • Knowledge helps in understanding how nutritional status, supplementation, medication, disease may affect breastfeeding or milk composition • Secretory cells in the breast uses 5 pathways for milk secretion • Water, sodium, potassium, chloride are able to pass through alveolar cell membranes in either direction -passive diffusion • Milk fat comes from triglycerides from the mother’s blood and from new fatty acids produced in the breast -fats are made soluble in milk by adding a protein carrier to form milk fat globules • Immunoglobulin A and other plasma proteins are captured from mother’s blood and taken into alveolar cells -then secreted into milk ducts The Letdown Reflex • Stimuli of infant suckling pass through the nerves of hypothalamus which promotes oxytocin release from posterior pituitary gland • Oxytocin causes contraction of myoepithelial cells surrounding the secretory cells HUMAN MILK COMPOSITION • Elegantly designed natural resource • Only food needed by majority of healthy infants for approx 6 months • Milk composition is designed to nurture and protect infants from infections and certain chronic diseases Colostrum • Milk produced in the first 2-3 days after the baby is born  Lactogenesis 2 -thick often yellow fluid • Is higher in protein and lower in lactose than milk produced after a milk supply is established • Secretory immunoglobulin A and lactoferrin are primary proteins present • Concentration of mononuclear cells is highest in colostrum -specific white blood cell from mother that provides immune protection • Higher concentrations of sodium, potassium, chloride than more mature milk Water • Breast milk is isotonic with plasma • This means babies don’t need water to maintain hydration • Allows suspension of milk sugars, proteins, immunoglobulin A, sodium, potassium, citrate, chloride, calcium and water soluble vitamins Energy • Human milk provides 0.65 kcal/mL -energy content varies with its fat • Breastfed infants consume fewer calories than infants fed HMS Lipids • Second largest component of breast milk by concentration, 3-5% in mature milk • Provide half the energy of human milk • The fatty acid profile of human milk varies based on the diet of the mother • Milk DHA levels are increased by maternal supplementation -docosahexaenioic acid • DHA is essential for retinal development and accumulates during last months of pregnancy • Fatty acids stemming from the mother’s diet are present in human milk -trans fats of American and Canadian women are similar but women in Europe have lower levels • Cholesterol is needed for growth and replication of cells -breastfed infants have higher intakes of cholesterol levels than infants fed HMS -early consumption of cholesterol from breast milk appears to be related to lower blood cholesterol levels later in life • Protein content of mature human milk is relatively low compared to other mammal milk -protein and their digestive products exhibit a variety of antiviral and antimicrobial effects • Casein is a major class of protein in mature milk from women who deliver at term or preterm -casein’s digestive products keep calcium in soluble form and facilitate its absorption • Whey proteins are proteins that remain soluble in water after casein is precipitated from milk by acid or enzymes -includes milk and serum proteins, enzymes, immunoglobulins -enzymes in whey protein aid in digestion and protection against bacteria • Non-protein nitrogen provides for 20-25% of nitrogen in milk • Some nitrogen in available for producing nonessential amino acids, some non-protein nitrogen is used to produce other proteins with biological roles Milk Carbohydrates • Lactose is the dominant carbohydrate in human milk • Lactose enhances calcium absorption • Oligosaccharides contribute calories at low osmolality (a measure of the concentration of particles in solution), stimulate growth of bifidus bacteria in the gut, inhibit the growth of E. coli and other harmful bacteria • Oligosaccharides can be free, bound to proteins as glycoproteins, bound to lipids as glycolipids -Conjugated or unconjugated oligosaccharides are classified as glycans Fat Soluble Vitamins • Vitamin A in human milk is in the form of beta-carotene -responsible for the characteristic yellow color of colostrum • Vitamin D is present in both lipid and aqueous compartments of human milk -varies with maternal diets, exposures to sunlight • Vitamin E: level of tocopherols in human milk is related to the milk content - levels of alpha-tocopherol decrease from colostrum to transitional milk to mature milk -whereas beta and gamma tocopherols remain stable throughout each stage of lactation -needed for muscle integrity and resistance of red blood cells to hemolysis (breaking of red blood cells) • Vitamin K: about 5% of breastfed infants are at risk for vit K deficiency Water Soluble Vitamins • Generally responsive to the content of the maternal diet or supplements • Clinical problems are rare in infants nursed by mothers with inadequate diets • Vitamin B6 is considered most likely to be deficient in human milk, they directly reflect maternal intake • Vitamin B12 an Folic Acid are bound to whey proteins in human milk, their content in milk is less influenced by maternal intake of these vitamins -factors that influence the protein secretion are likely to alter the human milk levels of B12 and folate than is dietary intake -deficiencies have been reported in milk from women who have had gastric bypass surgery, have hypothyroidism, consume vegan diets, have latent pernicious anemia, are malnourished • Folate levels increase with the duration of lactation despite a decrease in maternal serum and red blood cell folate levels Minerals in Human Milk • Moonovalent ion (atom with an electrical charge or +/- 1 ) secretion is managed closely by the alveolar cells , in balance with lactose, to maintain the isosmatic composition of human milk • Mineral content in milk is related to the growth rate of the offspring • Mineral concentration decreases over the first 4 months postpartum -is easier for the kidneys to handle, is a significant benefit of human milk • Bioavailability: the packaging of minerals in human milk makes them highly available to the infant -efficient use by the infant of minerals reduces the burden to the mother because less of the mineral is needed in the milk • Exclusively breastfed infants have little risk of anemia • Human milk zinc is bound to protein and is highly available -both zinc intake and the requirement of infants decline after the first few months -zinc homeostasis and human zinc levels are maintained even if maternal zinc levels are low • Trace minerals are present in the human body in small concentrations and are essential for growth and development -copper, selenium, chromium, manganese, molybdenum, nickel, fluorine -fluorine provided in community water is safe for breastfeeding mothers and their infants Taste of Human Milk • Breastfeeding woman’s diet influences the composition of her milk and has a long lasting influence on the infant • The flavour of human milk is slightly sweeter and carries the flavours of compounds ingested • The transfer of flavour compounds appears to occur selectively and in relatively low amounts • Exposing infants to a variety flavours in human milk may contribute to their interest in and consumption of human milks as well as their acceptance of flavours in solid foods BENEFITS OF BREASTFEEDING Breastfeeding Benefits for Mothers • Breastfeeding women experience hormonal, physical and psychosocial benefits • It immediately increases levels of oxytocin, which stimulates uterine contractions, minimizes maternal postpartum blood loss, help uterus to return to non-pregnant size • The return of fertility id delayed in most women during breastfeeding -the delay in ovulation results in longer intervals between pregnancies • Increased self confidence and facilitated bonding with the infant Breastfeeding Benefits for Infants 1. Nutritional benefits: • Human milk provides optimal nutrition to the infant • Nutrients in human milk matches infant requirements for growth and developments • Human milk is isosmotic therefore meets the requirements for food and water • Relatively low protein content in breast milk does not overload the infant’s kidneys with nitrogen • Whey protein in human milk forms a soft, easily digestible curd • Provides generous amounts of lipids • Long chained polyunsaturated fatty acids especially DHA are present, necessary for optimal development of central nervous system • Minerals in breast milk are easily available and press minimal demands on maternal reserves 2. Immunological Benefits • The ability of human milk to protect against infections • Cells, secretory immunoglobins, histocompatibility antigens, T-cell products, carrier proteins, enzymes are components that confer immunological benefits • Cellular components in human milk are especially high in colostrum but are also present for month in mature human milk • Macrophages: white blood cell that acts mainly through phagocytosis - kills bacteria, produces complement proteins • Leukocyte function offers more protection to the breast than to immunocompetence of the infant • Bifidus is a growth factor that supports the growth of Lactobacillus bifidus -it’s a probiotic bacterium that stimulates antibody production and enhances phagocytosis of antigens • Lysozyme protects against enterobacteria and gram positive bacteria - it’s secreted by neutrophils and macrophages 3. Lower infant mortality in developing countries • Improving breastfeeding practices can save approx 1.3 million lives annually • Reduces the risk of sudden infant death syndrome (SIDS) 4. Fewer acute illnesses • Reduced infant illness in countries with high infant morbidity (rate of illness in a population) and mortality (rate of death), poor sanitation and questionable water supplies 5. Reductions in chronic illness • Breastfeeding seems to protect against chronic childhood diseases • May reduce the risk of celiac disease, inflammatory bowel disease, neuroblastoma • Risk of allergy and asthmatic diseases are reduced during breastfeeding 6. Breastfeeding and childhood overweight • Breastfed children are typically leaner than children fed HMS • Literature suggests there is a small reduction in risk of overweight children older than 3 years who were breastfed potential mechanism for reducing obesity in children is the metabolic programming related to neurometabolic messengers delivered in human milk 7. Metabolic benefits • The duration of breastfeeding is linked with cognitive benefits, assessed by IQ • Increases in cognitive benefits associated with breastfeeding are significant even
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