7) Breast Milk Composition (Part II) Flashcards
Milk fat forms what percentage of milk by weight?
2.9 to 5.5%
What percentage of milk fat is composed of triacylglycerols? What forms the rest?
- 98%
- Diacylglycerols, monoacylglycerols, cholesterol, cholesterol esters, free fatty acids, phospholipids
Describe the composition of milk fat globules.
- The core is composed of triacylglycerols
- The membrane contains phospholipids, cholesterol and proteins
What forms the main source of energy in milk? Why?
- Triacylglycerols
- It is the most efficient way of delivering energy to the infant given their small stomach size
- It is more efficiently transformed into adipose tissue than carbohydrate and protein
How does the metabolic cost of fat compare to carbohydrates for the synthesis of adipose tissue storage?
- Fat has a low metabolic cost
- Carbohydrates have a high metabolic cost
Where are fatty acids with a backbone of fewer than 16 carbons synthesized?
In alveolar cells within the mammary gland from glucose
Where are fatty acids with a backbone of greater than 18 carbons synthesized?
From maternal adipose tissue stores and the diet
What are the effects of an increase in prolactin during lactation in terms of maternal milk lipid synthesis? (2)
1) Increases lipoprotein lipase (LPL) activity within the mammary gland
2) Increases free fatty acid uptake into the mammary gland
What occurs to the activity of lipoprotein lipase in maternal adipose tissue stores during lactation? What is the effect?
- Activity of LPL decreases
- The adipose tissue takes up less fatty acids
- Aids in the transport of FAs from the adipose tissue to the mammary tissue
Human milk contains a higher proportion of ______ at the second carbon position of triacylglycerols.
palmitate
What is the primary saturated fatty acid in cow and human milk fat?
Palmitic acid
How do monoacylglycerols containing palmitic acid at the second position compare to free palmitic acid in terms of absorption?
- Monoacylglycerols containing palmitic acid are better absorbed than free palmitic acid
- Human milk contains a higher proportion of palmitate at the second position
What creates non-soluble calcium soaps? What is the consequence?
- Saturated free fatty acids within the GI tract combining with calcium
- Lowers the bioavailability of calcium and prevents its absorption
How do monoacylglycerols containing a saturated fatty acid form a non-soluble calcium soap?
They do NOT form non-soluble calcium soaps
How does human milk compare to cow’s milk in terms of lipolytic activity?
Human milk has better lipolytic activity
Which type of lipase is less present in newborns? Why?
- Pancreatic lipase
- Due to a certain immaturity in terms of the exocrine function of the pancreas
Which types of lipids contained within breast milk require less bile salts for emulsification? Why? What is the consequence?
- Short-chain fatty acids, PUFAs, monounsaturated fatty acids
- Contain lower melting points
- Increases their likelihood of absorption
How does the quantity of oleic acid and saturated fatty acids compare between breast milk and cow’s milk?
- Greater quantity of oleic acid in breast milk
- Lower quantity of saturated fatty acids in breast milk
Non-soluble calcium soaps lower the bioavailability of which nutrients?
- Fat
- Calcium
- Magnesium
How does the quantity of EFAs compare between breast milk and cow’s milk? How does that compare to infant formula?
- Breast milk contains 5x more EFAs than cow’s milk
- Infant formula may contain more EFAs than breast milk
How does the quantity of long-chain PUFAs compare between breast milk and infant formulas?
They are contained in higher quantities in human breast milk
Is the quantity of DHA in breast milk dependent on the diet? Is the quantity of arachidonic acid in breast milk dependent on the diet?
- DHA: dependent on the diet
- Arachidonic acid: not dependent on the diet
Are essential fatty acid precursors sufficient for a newborn? Why or why not?
No, as they are developmentally immature and lack elongase and desaturase enzymes, required to form EFAs
How does the calcium to phosphorus ratio differ between breast milk and cow’s milk?
- 2 : 1 in breast milk
- 1.5 : 1 in cow’s milk
What is the effect of a greater quantity of phosphorus in relation to calcium in cow’s milk?
- Causes an increase in calcium excretion within the gut
- Decreases the absorption of calcium
There is a (lower/higher) solute load in human breast milk.
lower
Why is there a lower stress on the kidneys of the infant if they consume breast milk?
Because there is a lower protein content and a lower solute load
What is the least variable component within breast milk? Why?
- Lactose
- As it regulates 60 to 70% of the osmotic pressure of milk
- The maintenance of osmolarity maintains the energy cost of lactation low
How does diet influence the concentration of lactose in breast milk?
Diet does not influence the concentration of lactose in breast milk
How does lactose aid in mineral absorption?
Forms soluble chelates, preventing these minerals from precipitating within the duodenum due to its alkaline pH
How does pre-term milk compare to term milk?
- Pre-term milk is higher in energy, protein, sodium and chloride
- Pre-term milk is lower in lactose
Why is pre-term milk not optimal for infant consumption? What is recommended?
- Because it contains insufficient amounts of calcium, phosphorus, magnesium, and vitamin D
- Pumping followed by fortification is recommended
What decreases in breast milk in response to an increased length of lactation?
- Total protein
- Immunoglobulins
- Fat-soluble vitamins
What increases in breast milk in response to an increased length of lactation?
- Lactose
- Fat
- Energy
- Water-soluble vitamins
How does the fatty acid content differ between colostrum and mature milk?
Colostrum has a lower fatty acid content
How does the proportion of fatty acids change in response to an increased length of lactation?
Higher proportion of medium-chain fatty acids and palmitoleic acid
What explains the higher proportion of medium-chain fatty acids as lactation progresses?
- The rate of nerve cell division decreases (lower quantity of DHA required)
- Increase in myelination of nerve cells, which requires medium-chain fatty acids
What are major factors that influence breast milk composition?
- Gestational age (pre-term versus term)
- Time of day
- Maternal body fat content
- Type of maternal fat consumed
How does malnutrition affect immune factors?
- No effect on immune factors in mature milk
- Decrease in immune factors in colostrum
Which type of malnutrition may affect protein and immune factor components in breast milk?
Severe protein-energy malnutrition
How does diet influence breast milk composition?
There is no evidence that alterations in maternal diet affect the total milk fat content or milk volume
How does maternal body fat content influence breast milk composition?
- An increase in maternal body fat content increases the concentration of fat within breast milk
- The impact of the diet is dependent on prior nutritional status of the mother
What is the effect of insufficient maternal fat reserves accumulated during pregnancy?
May cause breast milk fat content to decrease
How do changes in the diet influence cholesterol and phospholipid content of milk?
Changes in the diet do not affect cholesterol and phospholipid content in milk
How does the quantity of linoleic acid in breast milk vary between vegetarian and omnivore mothers?
- Vegetarians: over 30% linoleic acid
- Omnivores: 6.9 to 18% linoleic acid
A low-fat and energy-restricted diet increases the proportion of which fatty acids within breast milk? Why?
- C16:0 and long-chain saturated fatty acids
- As there is an insufficient ingestion of EFAs, which increases the quantity of fatty acids mobilized from maternal fat stores
Which fatty acids are contained in low quantities in breast milk derived from vegan mothers?
- DHA (omega-3 fatty acids): insufficient amounts
- They receive sufficient quantities of omega-6 fatty acids
Which fat-soluble vitamin is the only one that is affected by maternal malnutrition?
- Vitamin D
- If there is insufficient ingestion of vitamin D or insufficient sun exposure, there will be poor vitamin D in breast milk
How are fat-soluble vitamins influenced by malnutrition? How are water-soluble vitamins influenced by malnutrition?
- Fat-soluble vitamins are not very affected by maternal malnutrition (apart from vitamin D)
- Water-soluble vitamins are generally affected by malnutrition
Which water-soluble vitamins are affected by malnutrition?
- Vitamin B12
- Vitamin B1
- Vitamin B6
- Vitamin C
Which breast milk minerals are closely associated with maternal dietary intake?
- Selenium
- Iodine
Why do fetuses possess a greater risk of environmental contaminants than for breastfed infants? (3)
1) More sensitive CNS
2) Higher dose per kg of body weight
3) Less fat tissue to store contaminants, increasing their availability to other areas of the body
What are the effects of PCBs and dioxins in breast milk?
- May interfere with vitamin K metabolism
- Linked to the late hemorrhagic disease of the newborn
Where do PCBs and dioxins in breast milk majorly arise from?
Stored levels in maternal adipose tissue
Which vitamin deficiencies may arise from exclusive breastfeeding?
- Vitamin K
- Vitamin D
- Iron (if iron-rich foods are not introduced after 6 months)
What increases the risk for vitamin K deficiency in newborns? (2)
- Breast milk contains low quantities of vitamin K
- The newborn has a sterile gut, which means that they do not possess bacteria to synthesize vitamin K
What do newborns require to prevent the risk of bleeding to death?
Mandatory injection of vitamin K is given at birth to allow for the proper synthesis of prothrombin
How do dioxins and PCBs interfere with vitamin K metabolism?
- They induce the activity of cytochrome P450
- Gamma-glutamyl carboxylase in cytochrome P450 requires vitamin K as a co-enzyme
- Vitamin K is not recycled in the normal salvage pathway, but is instead metabolized and excreted
What must be considered in terms of drug intake during lactation?
Type, half-life, dose, and duration of use
Which drugs are completely contraindicated during lactation?
Hallucinogenic drugs
If a mother is taking anti-convulsants, the infant may require ________ supplements.
vitamin K
Why is the mini-pill prescribed to lactating women instead of the contraceptive pill?
- The contraceptive pill containing estrogen and progesterone may cause gynecomastia in young infants and suppress lactation
- The mini-pill just contains progesterone
What are the effects of antibiotics in breast milk?
May cause allergic reactions, sleepiness, vomiting, diarrhea, and a refusal to eat in the infant
What are the effects of a caffeine intake above 1 to 2 cups a day in breast milk?
May cause restlessness, irritability, and sleeplessness in the infant
What is the effect of a sedative in breast milk?
Causes lethargy in infants
What is the effect of smoking in breast milk?
Decreases milk volume
What are the effects of alcohol in breast milk?
- Alcohol depresses the infant’s intake of milk
- The milk produced is decreased by alcohol
Which in-born error of metabolism prevents the infant from consuming breast milk?
- Phenylketonuria (PKU)
- The infant must ingest a formula with a low-phenylalanine content
What is galactosemia?
- Rare autosomal recessive disorder
- Causes a deficiency in 1-P-uridyl transferase
- Infants with galactosemia may not consume breast milk
What is the effect of a deficiency of 1-P-uridyl transferase?
- Prevents the conversion of galactose to UDP-galactose
- Galactose-1-phosphate accumulates
What metabolite is produced from the accumulation of galactose-1-phosphate?
Galactitol
What are the symptoms of galactosemia?
- Severe mental retardation
- Cataracts
- Liver damage
What are recommendations for breastfeeding in mothers with HIV?
- Breastfeeding must be done exclusively throughout six months
- Mix-feeding is NOT recommended
Why is breastfeeding alone not recommended for pre-term infants? What is recommended instead?
- Because there is insufficient calcium and phosphorus in the maternal milk that is provided by pre-term infants
- Mothers are recommended to pump, and the milk is then fortified with the lacking nutrients
When does breast milk jaundice occur? When does it end?
- Relatively uncommon (2 to 4% of infants)
- Occurs on the fourth day of life
- Ends on day 5 to 15
How does breast milk jaundice develop?
- As metabolites of progesterone travel to the infant’s bloodstream
- Specifically, 5B-pregnane-3a,20B-diol
- Inhibits bilirubin conjugation by glucoronyl transferase
- Jaundice occurs as bilirubin accumulates
What is the treatment for breast milk jaundice?
Phototherapy, in which a fluorescent light is absorbed by the skin of the infant, which converts the bilirubin molecules to water-soluble isomers
Is breastfeeding recommended to be withheld in infants with breast milk jaundice?
- If it is extremely severe, then yes, but only for a short period of time
- It is not recommended in most cases
What is the onset of eczema during breastfeeding associated with?
- The blunting of growth
- Symptoms of atopic eczema and rates of growth improve after breastfeeding is discontinued
What are possible consequences for prolonged breastfeeding beyond the age of 6 months?
- Reduced growth rate
- Feeding aversion
______ deficiency may be observed after 6 months when an infant is breastfed exclusively.
- Iron
- Iron-rich foods must be introduced after 6 months, when the infant’s iron stores become depleted
Are vitamin D supplements recommended for breastfed infants? Why or why not?
- Breastfed infants may be protected from vitamin D deficiency
- But, vitamin D supplements are recommended due to poor exposure to sunlight in Northern climates
Which vitamin deficiency may lead to late hemorrhagic disease of the newborn?
Vitamin K
