Transcript Psychology 3533 Understanding Human Sexuality

LACTATION
HUMAN LACTATION:
 Mammals perfected milk for their young
over millions of years of evolution.
 Each species has the perfect milk for its
own young, for optimal adaptation to
environmental demands. Chemical
composition very varied.
 Twentieth century massive experiment on
humans: using another species’ milk. Too
recent to know long-term consequences.
LACTATION
Lactation Hormones:
Prolactin:
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pituitary stimulates breast glands to produce milk.
Levels of prolactin increase during gestation.
Oxytocin:
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pituitary releases it as a response to stimulation of
nipple and areola. Oxytocin contracts alveoli of breast
glands, releasing milk into ducts. “Let down” reflex,
milk ejected through nipple openings.
Production of both hormones responds to demand:
more sucking, more hormonal output.
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 Physiological
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mechanism:
Infant’s suckling stimulates nipple
Neural stimulus reaches mother’s
hypothalamus
Hypothalamus stimulates pituitary
Pituitary releases oxytocin
Oxytocin contracts mammary gland
Milk is released into milk ducts and to nipple
Colostrum
 Amount
of milk produced is positively
correlated with amount of suckling.
LACTATION
 Advantages
for infant:
 Nutritional:
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smooth adaptation period from intra to extrauterine life (shortened gestation – 9 months
instead of 12 as other primates)
perfected over millions of years of evolution,
right amounts of the right nutrients
species-specific: each species has different
developmental needs
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 Advantages
for infant:
 Nutritional (Cont’d):
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living tissue that changes according to infant’s
needs (age, growth spurt, environmental
temperature, pathogens)
different composition for premies
brain development: cisteine, taurine,
docosahexanoic acid, arachidonic acid, other
aminoacids and nucleotides
LACTATION
 Advantages
for infant:
 Nutritional (Cont’d):
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non-allergenic
100% digestible, no waste
lower renal solute
unlikely to overfeed due to changing
composition through a feed: lower risk of later
obesity
bioavailability of nutrients
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 Immunological
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advantages:
fresh antibodies in each drop (infant has
immature immune system)
macrophages, lymphocytes, neutrophiles
mammary gland makes antibodies in situ
when a new pathogen appears in the
environment
enteromammary antibodies
bronchomammary antibodies
LACTATION
 Immunological
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advantages (Cont’d):
lactobacillus bifidus prevents gut colonization
by harmful bacteria
lactoferrin kills staph and E-coli
B12 transfer factor starves bacteria
antiviral factor
interferon
 Therefore:
lower morbidity and mortality
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 Other
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advantages:
much lower SIDS incidence
better oral health
better oral cavity conformation
secure, happy
bonding, closeness
better skin
better smell (hair, skin, excretions)
long term health
good foundation for attachment
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Benefits for lactating mother:
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uterus back to pre-pregnant state due to oxytocin-induced
contractions
contraception**
breast cancer protection
skeletal calcium deposits (lower osteoporosis risk)
weight loss
stress control (hormonal)
economic
convenience
bonding
empowerment, self-assurance
pleasure
lower incidence of rheumatoid arthritis
lower incidence of Type II diabetes
delays recurrence of MS (Multiple Sclerosis)
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Other advantages of breastfeeding:
 Protection against some cancers for both
mother and infant.
 Lessens the risk of heart disease later in
life (for infant).
 Non-breastfed infants have higher
cholesterol levels in adolescence.
 Positive effect on bone mineral density for
both mother and infant. More efficient
calcium absorption.
LACTATION
Other advantages of breastfeeding (Cont’d):
 Breastfed infants score higher on the
psychomotor and mental scales of the
Bayley Scales.
 Reduced dental caries in breastfed infants.
 Protection and enhancement of vision for
infants.
 Two months of breastfeeding resulted in
absence of coronary artery disease in
adolescents.
LACTATION
Other advantages of breastfeeding (Cont’d):
 Better lipid absorption. Lipids (fats) are
necessary for brain development and cell
membrane health.
 Significantly lower cholesterol in 30-year-old
adults who were breastfed for six months.
 Because of the chemical composition of cow’s
milk-based formula, iron is less bioavailable.
Adding iron to infant’s diet often causes
intestinal bleeding, which leads to loss of iron.
 Composition of human milk changes every few
minutes during a feed. E.g. much higher fat
content after some 20 minutes. This causes
baby to stop nursing, or nurse shallowly,
therefore not overfeeding.
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ENVIRONMENTAL BENEFITS:
 Packaging of formulas: cans, bottles, rubber
nipples, labels (thousands of tons of plastic,
metal, paper, etc. each).
 Pollution of land and groundwater, toxic fumes
on incineration.
 Like all cattle-based food, significant contribution
to pollution, acid rain, deforestation and soil
erosion.
 Industrial processing to produce formulas uses
vast quantities of energy, natural resources.