NUTR2003 Lecture Notes - Lecture 6: Prolactin, Ovulation, Fish Oil
NUTR2003 LECTURE SIX
NUTRITION DURING LACTATION
• Lactation physiology
• Human milk consumption
• Maternal dietary needs
• Benefits of breastfeeding
• Barriers to breastfeeding
Australian National Breastfeeding Strategy 2000-2015:
Dietary Guidelines for Australians: 2013
Guideline 4: Encourage and support breastfeeding
Physiology Terms:
Mammary gland: AKA breast
Alveoli: rounded shaped cavity present in breast
Secretory cells: cells in acinus (milk gland) responsible for secreting milk components into ducts
Myoepithelial cells: line the alveoli and can contract to cause milk to be secreted into ducts
Oxytocin: hormone produced during letdown that causes milk to eject into ducts
Lactiferous sinuses: larger ducts for storage of milk behind nipple
Lobes: rounded structures of mammary glands
Mammary Gland Development
• During puberty, the ovaries mature with increases in oestrogen and progesterone
• Hormones impacting lactation and their functions:
Stages of Lactogenesis
I: birth to 2-5 days, milk formation begins
II: begins 2-5 days after birth, increased blood flow to breast; milk 'comes in'
III: begins at ~10 days after birth, milk composition is stable
find more resources at oneclass.com
find more resources at oneclass.com
Hormonal Control of Lactation
1. Prolactin:
• Stimulates milk production
• Released in response to suckling, stress, sleep and sexual intercourse
• Inhibits ovulation
2. Oxytocin:
• Stimulates letdown/ ejection
• Tingling of the breast may occur corresponding to contractions in milk ducts
• Causes uterus to contract, seal blood vessels, and shrink in size
The Letdown Reflex: Triggered by infant suckling
Human Milk Composition:
• Only food needed by the majority of healthy infants for ~6 months
• Nurtures and protects infants from infectious disease
Composition changes over a single feeding/over a day, based on:
Infant age
Present of infection in breast
Menses
Maternal nutrition status
Colostrum:
• The first milk secreted during the first few days postpartum
• Small amount for immature digestive system
• 'Paints' digestive tract
• Low fat for easy digestion
• Contains mother's antibodies which boost infants' immune system
• Acts as a laxative
Milk transition:
• Transitional milk up to 2 weeks: may still have yellow appearance
• Amounts increase quickly as infant hungers and digestive system matures
• Mature milk: supply/demand system engorgement decreases
Water and Energy in Human Milk:
Water:
• Major component in human milk
• Isotonic with maternal plasma
• Changes with external temperature
Energy:
find more resources at oneclass.com
find more resources at oneclass.com
• ~0.65kcal/ml
• Lower in calories than human milk substitute (HMS)
Lipids in Human Milk:
• 1/2 calories
• Fatty acid profile reflects mother's dietary intake (i.e. low fat diet with adequate CHO and protein,
milk is increased in medium-chain fatty acids)
DHA, Trans Fatty Acids and Cholesterol in Human Milk
DHA (docosahexaenoic acid)
• Essential for retinal development
• Associated with higher IQ scores
Trans fatty acids:
• Present in human milk from maternal diet
Cholesterol:
• Higher in human milk than HMS
• Early consumption of cholesterol through breast milk appears to be related to lower blood
cholesterol levels later in life
Proteins in Human Milk:
Total:
• Lower than in whole cow's milk
• Antiviral and antimicrobial effects
Casin:
• Main protein in mature human milk
• Facilitates calcium absorption
Whey:
• Soluble, precipitates by acid or enzyme
• Some minerals, hormones and vitamin binding proteins are part of whey
Non-protein nitrogen:
• ~20-25% nitrogen in human milk
• Used to make non-essential amino acids
Milk Carbohydrates:
Lactose:
• Dominant CHO
• Enhances Ca2+ absorption
Oligosaccharides:
• Medium length CHO
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Nutrition during lactation: human milk consumption, maternal dietary needs, benefits of breastfeeding, barriers to breastfeeding. Secretory cells: cells in acinus (milk gland) responsible for secreting milk components into ducts. Myoepithelial cells: line the alveoli and can contract to cause milk to be secreted into ducts. Oxytocin: hormone produced during letdown that causes milk to eject into ducts. Lactiferous sinuses: larger ducts for storage of milk behind nipple. Mammary gland development: during puberty, the ovaries mature with increases in oestrogen and progesterone, hormones impacting lactation and their functions: I: birth to 2-5 days, milk formation begins. Ii: begins 2-5 days after birth, increased blood flow to breast; milk "comes in" Iii: begins at ~10 days after birth, milk composition is stable. Human milk composition: only food needed by the majority of healthy infants for ~6 months, nurtures and protects infants from infectious disease. Composition changes over a single feeding/over a day, based on:
