Nutrition During Lactation Part 1

Nutrition During Lactation (Part 1)

• General Outcome: Understand physiological changes during lactation and its relation to nutrition, summarize benefits of breastfeeding, and understand factors affecting breastfeeding.

• Specific Outcomes: Describe mammary gland development, structure, and function; describe hormonal influences on development and function; describe benefits of breastfeeding for mother and infant; and describe barriers to breastfeeding and ways to overcome them.

Development of Mammary Gland

• Estrogen and progesterone increase during puberty and influence pubertal breast development.
• During pregnancy, estrogen stimulates development of milk-producing mammary glands.
• Breasts produce milk from water and nutrients.
• Milk is stored in lobules until oxytocin signals muscles in lobules to contract and push milk through ducts.

Functional Units of the Mammary Gland

• Alveoli are the fundamental units of the mammary gland.
• Each alveolus comprises secretory cells with a duct in the center.
• Ducts are arranged like branches of a tree.
• Myoepithelial cells surround secretory cells; contract under oxytocin influence to eject milk into ducts.

Lactogenesis

• Lactogenesis is another term for human milk production.
• Three main stages of lactogenesis:
  • Stage I: Begins at the end of the trimester (12 weeks before delivery); milk begins to form; lactose and protein in milk increase.
  • Stage II: 2 to 5 days after birth; increase in blood flow to mammary gland; delayed stage II is associated with failure to sustain breastfeeding.
  • Stage III: About ten days after birth; also called galactopoiesis; milk composition becomes stable.

Hormonal Control of Lactation

• Prolactin: Stimulates milk production; stimulated by suckling; also influenced by stress, sleep, and exercise; prolactin level in blood not related to amount of milk produced; level may drop if breast not stimulated to produce milk.
• Oxytocin: Involves in ejection of milk from milk glands; stimulated by suckling; also acts on uterus during and after delivery (causing contraction, sealing blood vessels, and shrinking its size).

Secretion of Milk

• Lactose: Formed in secretory cells.
• Milk fat: Comes from maternal triglycerides and fatty acids produced in breasts; actively transported from cell into milk.
• Sodium, potassium, and water: Actively transported from the cell into milk.
• Proteins: Captured from the mother's blood through transcytosis.
• Leukocytes: Pass directly between cells.

Letdown Reflex

• This is also called the milk ejection reflex.
• It's a natural response happening when the body releases milk from the breasts during breastfeeding.
• Stimulation occurs when the baby sucks on the breast, stimulating sensory nerve endings.
• Signals are sent to the brain to release oxytocin.
• Oxytocin causes muscles around alvéoli to contract, pushing milk through ducts and out of the nipple for the baby to drink.

Human Milk Composition

• Human milk is the only food needed for infants for first six months.
• Composition is variable over a feeding and changes according to infant age, gestational age at delivery, breast infections, maternal nutritional status, geographical location.
• Many components of human milk have been identified, and their nutritive and non-nutritive roles remain under investigation.

Human Milk Composition - Colostrum

• A thick, yellow fluid produced during lactogenesis II (days 1-3 after infant birth).
• Infants may only consume 2-20 mL (0.5-4 tsp) per feeding in the first two to three days.
• Contains high immunoglobulin A (provides antibodies) and lactoferrin (regulates iron absorption).
• Nutritional profile: (~580-700 kcal/L) containing protein, minerals, carbohydrate, fat & vitamins.

Human Milk Composition - Water & Energy

• Water: major component of human milk; isotonic with maternal plasma and babies don't need additional water or fluids to maintain hydration.
• Energy: Provides about 0.65-0.75 kcal/mL; fewer calories than human milk substitutes; enhanced growth in the first 3-4 months is seen in infants with prolonged and exclusive breastfeeding; at 8-11 months, breastfed infants are thinner than infants who consume human milk substitutes.

Human Milk Composition - Lipid

• Contributes half the calories in human milk; fat content is lower in foremilk and higher in hindmilk.
• Effect of maternal diet on fat composition; profile reflects dietary intake of mother.
• Important lipid components: DHA (essential for retinal development), trans fatty acids (present in human milk from maternal diet), cholesterol (needed for cell replication).
  • Foremilk: milk consumed at the beginning of feeding.
  • Hindmilk: milk obtained at the end of feedings

Human Milk Composition - Protein

• Protein content of mature human milk is relatively low.
• Concentration is influenced by infant age.
• Important nutritive and non-nutritive values.
• Exhibit a variety of antiviral and antimicrobial effects.
• Enzymes provide protection by preventing inflammation.
• Types of proteins: Casein and Whey.

Human Milk Composition - Carbohydrate

• Dominant carbohydrate is lactose.
• Enhances calcium absorption.
• Other carbohydrates: monosaccharides (glucose), polysaccharides, oligosaccharides, and protein-bound carbohydrates.
• Second largest carbohydrate component is oligosaccharides; contribute calories at low osmolality; stimulate growth of Bifidobacteria in the gut; inhibit growth of E.coli and other harmful bacteria.

Human Milk Composition - Fat-Soluble Vitamins

• Vitamin A: Colostrum contains twice the concentration of vitamin A compared to mature milk; some vitamin A is in the form of beta-carotene (yellow color). Important for calcium absorption and bone metabolism.
• Vitamin D: Content in milk is reflective of the mother's exposure to sunlight; maternal exposure can increase vitamin D3 level in milk.

Human Milk Composition - Fat-Soluble Vitamins (cont.)

• Vitamin E: Protects cells from oxidative damage; important for maintaining normal neurological structure and function; adequate in human milk to meet full-term infant needs for muscle and red blood cell integrity.
• Vitamin K: Used by the body to form clots and stop bleeding, about 5% of breastfed infants are at risk for vitamin K deficiency, intramuscular vitamin K at birth can prevent deficiency bleeding.

Human Milk Composition - Water-Soluble Vitamins

• Content is reflective of mother's diet or supplements.
• Milk from well-nourished women provides nutrients in quantities consistent with estimated needs of their babies.
• Folate is bound to whey protein, less influenced by maternal intake.
• Minerals like magnesium, calcium, iron, and zinc are packaged, making them highly available to infants; improving efficiency and reducing burden to the mother.
• Vitamin C and lactose in human milk promote iron absorption.

Taste of Human Milk

• Flavor of human milk is important for newborn infants - slightly sweet.
• Milk carries flavors of compounds ingested by the mother (e.g., mint, garlic, vanilla, alcohol).
• Transfer of flavor compounds is selective and in low amounts.
• Infants show more interest in mother's milk when flavors are new to them.
• Mothers should eat a variety of healthy foods.

Explore the physiological changes during lactation and their nutritional implications with this quiz. Understand the benefits of breastfeeding, mammary gland development, and the barriers mothers may face while breastfeeding. Perfect for those studying maternal and infant nutrition.