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HUMAN LACTATION:HUMAN LACTATION: Mammals perfected milk for their young Mammals perfected milk for their young

over millions of years of evolution.over millions of years of evolution. Each species has the perfect milk for its Each species has the perfect milk for its

own young, for optimal adaptation to own young, for optimal adaptation to environmental demands. Chemical environmental demands. Chemical composition very varied.composition very varied.

Twentieth century massive experiment on Twentieth century massive experiment on humans: using another species’ milk. Too humans: using another species’ milk. Too recent to know long-term consequences.recent to know long-term consequences.

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Lactation Hormones:Lactation Hormones:Prolactin:Prolactin:

pituitary stimulates breast glands to produce milk. pituitary stimulates breast glands to produce milk. Levels of prolactin increase during gestation.Levels of prolactin increase during gestation.

Oxytocin:Oxytocin: pituitary releases it as a response to stimulation of pituitary releases it as a response to stimulation of

nipple and areola. Oxytocin contracts alveoli of breast nipple and areola. Oxytocin contracts alveoli of breast glands, releasing milk into ducts. “Let down” reflex, glands, releasing milk into ducts. “Let down” reflex, milk ejected through nipple openings.milk ejected through nipple openings.

Production of both hormones responds to demand: Production of both hormones responds to demand: more sucking, more hormonal output.more sucking, more hormonal output.

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Physiological mechanism:Physiological mechanism: Infant’s suckling stimulates nippleInfant’s suckling stimulates nipple Neural stimulus reaches mother’s Neural stimulus reaches mother’s

hypothalamushypothalamus Hypothalamus stimulates pituitaryHypothalamus stimulates pituitary Pituitary releases oxytocinPituitary releases oxytocin Oxytocin contracts mammary glandOxytocin contracts mammary gland Milk is released into milk ducts and to nippleMilk is released into milk ducts and to nipple ColostrumColostrum

Amount of milk produced is positively Amount of milk produced is positively correlated with amount of suckling.correlated with amount of suckling.

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Advantages for infant:Advantages for infant: Nutritional:Nutritional:

smooth adaptation period from intra to extra-smooth adaptation period from intra to extra-uterine life (shortened gestation – 9 months uterine life (shortened gestation – 9 months instead of 12 as other primates)instead of 12 as other primates)

perfected over millions of years of evolution, perfected over millions of years of evolution, right amounts of the right nutrientsright amounts of the right nutrients

species-specific: each species has different species-specific: each species has different developmental needsdevelopmental needs

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Advantages for infant:Advantages for infant: Nutritional (Cont’d):Nutritional (Cont’d):

living tissue that changes according to infant’s living tissue that changes according to infant’s needs (age, growth spurt, environmental needs (age, growth spurt, environmental temperature, pathogens)temperature, pathogens)

different composition for premiesdifferent composition for premies brain development: cisteine, taurine, brain development: cisteine, taurine,

docosahexanoic acid, arachidonic acid, other docosahexanoic acid, arachidonic acid, other aminoacids and nucleotidesaminoacids and nucleotides

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Advantages for infant:Advantages for infant: Nutritional (Cont’d):Nutritional (Cont’d):

non-allergenicnon-allergenic 100% digestible, no waste100% digestible, no waste lower renal solutelower renal solute unlikely to overfeed due to changing unlikely to overfeed due to changing

composition through a feed: lower risk of later composition through a feed: lower risk of later obesityobesity

bioavailability of nutrientsbioavailability of nutrients

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Immunological advantages:Immunological advantages: fresh antibodies in each drop (infant has fresh antibodies in each drop (infant has

immature immune system)immature immune system) macrophages, lymphocytes, neutrophilesmacrophages, lymphocytes, neutrophiles mammary gland makes antibodies mammary gland makes antibodies in situin situ

when a new pathogen appears in the when a new pathogen appears in the environmentenvironment

enteromammary antibodiesenteromammary antibodies bronchomammary antibodiesbronchomammary antibodies

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Immunological advantages (Cont’d):Immunological advantages (Cont’d): lactobacillus bifidus lactobacillus bifidus prevents gut colonization prevents gut colonization

by harmful bacteriaby harmful bacteria lactoferrin kills staph and E-colilactoferrin kills staph and E-coli B12 transfer factor starves bacteriaB12 transfer factor starves bacteria antiviral factorantiviral factor interferoninterferon

Therefore: lower morbidity and mortalityTherefore: lower morbidity and mortality

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Other advantages:Other advantages: much lower SIDS incidencemuch lower SIDS incidence better oral healthbetter oral health better oral cavity conformationbetter oral cavity conformation secure, happysecure, happy bonding, closenessbonding, closeness better skinbetter skin better smell (hair, skin, excretions)better smell (hair, skin, excretions) long term healthlong term health good foundation for attachmentgood foundation for attachment

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Benefits for lactating mother:Benefits for lactating mother: uterus back to pre-pregnant state due to oxytocin-induced uterus back to pre-pregnant state due to oxytocin-induced

contractionscontractions contraception**contraception** breast cancer protectionbreast cancer protection skeletal calcium deposits (lower osteoporosis risk)skeletal calcium deposits (lower osteoporosis risk) weight lossweight loss stress control (hormonal)stress control (hormonal) economiceconomic convenienceconvenience bondingbonding empowerment, self-assuranceempowerment, self-assurance pleasurepleasure lower incidence of rheumatoid arthritislower incidence of rheumatoid arthritis lower incidence of Type II diabeteslower incidence of Type II diabetes delays recurrence of MS (Multiple Sclerosis)delays recurrence of MS (Multiple Sclerosis)

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Other advantages of breastfeeding:Other advantages of breastfeeding: Protection against some cancers for both Protection against some cancers for both

mother and infant.mother and infant. Lessens the risk of heart disease later in Lessens the risk of heart disease later in

life (for infant).life (for infant). Non-breastfed infants have higher Non-breastfed infants have higher

cholesterol levels in adolescence.cholesterol levels in adolescence. Positive effect on bone mineral density for Positive effect on bone mineral density for

both mother and infant. More efficient both mother and infant. More efficient calcium absorption.calcium absorption.

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Other advantages of breastfeeding (Cont’d):Other advantages of breastfeeding (Cont’d): Breastfed infants score higher on the Breastfed infants score higher on the

psychomotor and mental scales of the psychomotor and mental scales of the Bayley Scales.Bayley Scales.

Reduced dental caries in breastfed infants.Reduced dental caries in breastfed infants. Protection and enhancement of vision for Protection and enhancement of vision for

infants.infants. Two months of breastfeeding resulted in Two months of breastfeeding resulted in

absence of coronary artery disease in absence of coronary artery disease in adolescents.adolescents.

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Other advantages of breastfeeding (Cont’d):Other advantages of breastfeeding (Cont’d): Better lipid absorption. Lipids (fats) are Better lipid absorption. Lipids (fats) are

necessary for brain development and cell necessary for brain development and cell membrane health.membrane health.

Significantly lower cholesterol in 30-year-old Significantly lower cholesterol in 30-year-old adults who were breastfed for six months.adults who were breastfed for six months.

Because of the chemical composition of cow’s Because of the chemical composition of cow’s milk-based formula, iron is less bioavailable. milk-based formula, iron is less bioavailable. Adding iron to infant’s diet often causes Adding iron to infant’s diet often causes intestinal bleeding, which leads to loss of iron.intestinal bleeding, which leads to loss of iron.

Composition of human milk changes every few Composition of human milk changes every few minutes during a feed. E.g. much higher fat minutes during a feed. E.g. much higher fat content after some 20 minutes. This causes content after some 20 minutes. This causes baby to stop nursing, or nurse shallowly, baby to stop nursing, or nurse shallowly, therefore not overfeeding.therefore not overfeeding.

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ENVIRONMENTAL BENEFITS:ENVIRONMENTAL BENEFITS: Packaging of formulas: cans, bottles, rubber Packaging of formulas: cans, bottles, rubber

nipples, labels (thousands of tons of plastic, nipples, labels (thousands of tons of plastic, metal, paper, etc. each).metal, paper, etc. each).

Pollution of land and groundwater, toxic fumes Pollution of land and groundwater, toxic fumes on incineration.on incineration.

Like all cattle-based food, significant contribution Like all cattle-based food, significant contribution to pollution, acid rain, deforestation and soil to pollution, acid rain, deforestation and soil erosion.erosion.

Industrial processing to produce formulas uses Industrial processing to produce formulas uses vast quantities of energy, natural resources.vast quantities of energy, natural resources.