7) Breast Milk Composition (Part II) Flashcards

1
Q

Milk fat forms what percentage of milk by weight?

A

2.9 to 5.5%

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2
Q

What percentage of milk fat is composed of triacylglycerols? What forms the rest?

A
  • 98%

- Diacylglycerols, monoacylglycerols, cholesterol, cholesterol esters, free fatty acids, phospholipids

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3
Q

Describe the composition of milk fat globules.

A
  • The core is composed of triacylglycerols

- The membrane contains phospholipids, cholesterol and proteins

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4
Q

What forms the main source of energy in milk? Why?

A
  • 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
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5
Q

How does the metabolic cost of fat compare to carbohydrates for the synthesis of adipose tissue storage?

A
  • Fat has a low metabolic cost

- Carbohydrates have a high metabolic cost

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6
Q

Where are fatty acids with a backbone of fewer than 16 carbons synthesized?

A

In alveolar cells within the mammary gland from glucose

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7
Q

Where are fatty acids with a backbone of greater than 18 carbons synthesized?

A

From maternal adipose tissue stores and the diet

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8
Q

What are the effects of an increase in prolactin during lactation in terms of maternal milk lipid synthesis? (2)

A

1) Increases lipoprotein lipase (LPL) activity within the mammary gland
2) Increases free fatty acid uptake into the mammary gland

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9
Q

What occurs to the activity of lipoprotein lipase in maternal adipose tissue stores during lactation? What is the effect?

A
  • 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
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10
Q

Human milk contains a higher proportion of ______ at the second carbon position of triacylglycerols.

A

palmitate

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11
Q

What is the primary saturated fatty acid in cow and human milk fat?

A

Palmitic acid

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12
Q

How do monoacylglycerols containing palmitic acid at the second position compare to free palmitic acid in terms of absorption?

A
  • Monoacylglycerols containing palmitic acid are better absorbed than free palmitic acid
  • Human milk contains a higher proportion of palmitate at the second position
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13
Q

What creates non-soluble calcium soaps? What is the consequence?

A
  • Saturated free fatty acids within the GI tract combining with calcium
  • Lowers the bioavailability of calcium and prevents its absorption
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14
Q

How do monoacylglycerols containing a saturated fatty acid form a non-soluble calcium soap?

A

They do NOT form non-soluble calcium soaps

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15
Q

How does human milk compare to cow’s milk in terms of lipolytic activity?

A

Human milk has better lipolytic activity

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16
Q

Which type of lipase is less present in newborns? Why?

A
  • Pancreatic lipase

- Due to a certain immaturity in terms of the exocrine function of the pancreas

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17
Q

Which types of lipids contained within breast milk require less bile salts for emulsification? Why? What is the consequence?

A
  • Short-chain fatty acids, PUFAs, monounsaturated fatty acids
  • Contain lower melting points
  • Increases their likelihood of absorption
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18
Q

How does the quantity of oleic acid and saturated fatty acids compare between breast milk and cow’s milk?

A
  • Greater quantity of oleic acid in breast milk

- Lower quantity of saturated fatty acids in breast milk

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19
Q

Non-soluble calcium soaps lower the bioavailability of which nutrients?

A
  • Fat
  • Calcium
  • Magnesium
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20
Q

How does the quantity of EFAs compare between breast milk and cow’s milk? How does that compare to infant formula?

A
  • Breast milk contains 5x more EFAs than cow’s milk

- Infant formula may contain more EFAs than breast milk

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21
Q

How does the quantity of long-chain PUFAs compare between breast milk and infant formulas?

A

They are contained in higher quantities in human breast milk

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22
Q

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?

A
  • DHA: dependent on the diet

- Arachidonic acid: not dependent on the diet

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23
Q

Are essential fatty acid precursors sufficient for a newborn? Why or why not?

A

No, as they are developmentally immature and lack elongase and desaturase enzymes, required to form EFAs

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24
Q

How does the calcium to phosphorus ratio differ between breast milk and cow’s milk?

A
  • 2 : 1 in breast milk

- 1.5 : 1 in cow’s milk

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25
Q

What is the effect of a greater quantity of phosphorus in relation to calcium in cow’s milk?

A
  • Causes an increase in calcium excretion within the gut

- Decreases the absorption of calcium

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26
Q

There is a (lower/higher) solute load in human breast milk.

A

lower

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27
Q

Why is there a lower stress on the kidneys of the infant if they consume breast milk?

A

Because there is a lower protein content and a lower solute load

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28
Q

What is the least variable component within breast milk? Why?

A
  • Lactose
  • As it regulates 60 to 70% of the osmotic pressure of milk
  • The maintenance of osmolarity maintains the energy cost of lactation low
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29
Q

How does diet influence the concentration of lactose in breast milk?

A

Diet does not influence the concentration of lactose in breast milk

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30
Q

How does lactose aid in mineral absorption?

A

Forms soluble chelates, preventing these minerals from precipitating within the duodenum due to its alkaline pH

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31
Q

How does pre-term milk compare to term milk?

A
  • Pre-term milk is higher in energy, protein, sodium and chloride
  • Pre-term milk is lower in lactose
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32
Q

Why is pre-term milk not optimal for infant consumption? What is recommended?

A
  • Because it contains insufficient amounts of calcium, phosphorus, magnesium, and vitamin D
  • Pumping followed by fortification is recommended
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33
Q

What decreases in breast milk in response to an increased length of lactation?

A
  • Total protein
  • Immunoglobulins
  • Fat-soluble vitamins
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34
Q

What increases in breast milk in response to an increased length of lactation?

A
  • Lactose
  • Fat
  • Energy
  • Water-soluble vitamins
35
Q

How does the fatty acid content differ between colostrum and mature milk?

A

Colostrum has a lower fatty acid content

36
Q

How does the proportion of fatty acids change in response to an increased length of lactation?

A

Higher proportion of medium-chain fatty acids and palmitoleic acid

37
Q

What explains the higher proportion of medium-chain fatty acids as lactation progresses?

A
  • The rate of nerve cell division decreases (lower quantity of DHA required)
  • Increase in myelination of nerve cells, which requires medium-chain fatty acids
38
Q

What are major factors that influence breast milk composition?

A
  • Gestational age (pre-term versus term)
  • Time of day
  • Maternal body fat content
  • Type of maternal fat consumed
39
Q

How does malnutrition affect immune factors?

A
  • No effect on immune factors in mature milk

- Decrease in immune factors in colostrum

40
Q

Which type of malnutrition may affect protein and immune factor components in breast milk?

A

Severe protein-energy malnutrition

41
Q

How does diet influence breast milk composition?

A

There is no evidence that alterations in maternal diet affect the total milk fat content or milk volume

42
Q

How does maternal body fat content influence breast milk composition?

A
  • 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
43
Q

What is the effect of insufficient maternal fat reserves accumulated during pregnancy?

A

May cause breast milk fat content to decrease

44
Q

How do changes in the diet influence cholesterol and phospholipid content of milk?

A

Changes in the diet do not affect cholesterol and phospholipid content in milk

45
Q

How does the quantity of linoleic acid in breast milk vary between vegetarian and omnivore mothers?

A
  • Vegetarians: over 30% linoleic acid

- Omnivores: 6.9 to 18% linoleic acid

46
Q

A low-fat and energy-restricted diet increases the proportion of which fatty acids within breast milk? Why?

A
  • 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
47
Q

Which fatty acids are contained in low quantities in breast milk derived from vegan mothers?

A
  • DHA (omega-3 fatty acids): insufficient amounts

- They receive sufficient quantities of omega-6 fatty acids

48
Q

Which fat-soluble vitamin is the only one that is affected by maternal malnutrition?

A
  • Vitamin D
  • If there is insufficient ingestion of vitamin D or insufficient sun exposure, there will be poor vitamin D in breast milk
49
Q

How are fat-soluble vitamins influenced by malnutrition? How are water-soluble vitamins influenced by malnutrition?

A
  • Fat-soluble vitamins are not very affected by maternal malnutrition (apart from vitamin D)
  • Water-soluble vitamins are generally affected by malnutrition
50
Q

Which water-soluble vitamins are affected by malnutrition?

A
  • Vitamin B12
  • Vitamin B1
  • Vitamin B6
  • Vitamin C
51
Q

Which breast milk minerals are closely associated with maternal dietary intake?

A
  • Selenium

- Iodine

52
Q

Why do fetuses possess a greater risk of environmental contaminants than for breastfed infants? (3)

A

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

53
Q

What are the effects of PCBs and dioxins in breast milk?

A
  • May interfere with vitamin K metabolism

- Linked to the late hemorrhagic disease of the newborn

54
Q

Where do PCBs and dioxins in breast milk majorly arise from?

A

Stored levels in maternal adipose tissue

55
Q

Which vitamin deficiencies may arise from exclusive breastfeeding?

A
  • Vitamin K
  • Vitamin D
  • Iron (if iron-rich foods are not introduced after 6 months)
56
Q

What increases the risk for vitamin K deficiency in newborns? (2)

A
  • 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

57
Q

What do newborns require to prevent the risk of bleeding to death?

A

Mandatory injection of vitamin K is given at birth to allow for the proper synthesis of prothrombin

58
Q

How do dioxins and PCBs interfere with vitamin K metabolism?

A
  • 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
59
Q

What must be considered in terms of drug intake during lactation?

A

Type, half-life, dose, and duration of use

60
Q

Which drugs are completely contraindicated during lactation?

A

Hallucinogenic drugs

61
Q

If a mother is taking anti-convulsants, the infant may require ________ supplements.

A

vitamin K

62
Q

Why is the mini-pill prescribed to lactating women instead of the contraceptive pill?

A
  • The contraceptive pill containing estrogen and progesterone may cause gynecomastia in young infants and suppress lactation
  • The mini-pill just contains progesterone
63
Q

What are the effects of antibiotics in breast milk?

A

May cause allergic reactions, sleepiness, vomiting, diarrhea, and a refusal to eat in the infant

64
Q

What are the effects of a caffeine intake above 1 to 2 cups a day in breast milk?

A

May cause restlessness, irritability, and sleeplessness in the infant

65
Q

What is the effect of a sedative in breast milk?

A

Causes lethargy in infants

66
Q

What is the effect of smoking in breast milk?

A

Decreases milk volume

67
Q

What are the effects of alcohol in breast milk?

A
  • Alcohol depresses the infant’s intake of milk

- The milk produced is decreased by alcohol

68
Q

Which in-born error of metabolism prevents the infant from consuming breast milk?

A
  • Phenylketonuria (PKU)

- The infant must ingest a formula with a low-phenylalanine content

69
Q

What is galactosemia?

A
  • Rare autosomal recessive disorder
  • Causes a deficiency in 1-P-uridyl transferase
  • Infants with galactosemia may not consume breast milk
70
Q

What is the effect of a deficiency of 1-P-uridyl transferase?

A
  • Prevents the conversion of galactose to UDP-galactose

- Galactose-1-phosphate accumulates

71
Q

What metabolite is produced from the accumulation of galactose-1-phosphate?

A

Galactitol

72
Q

What are the symptoms of galactosemia?

A
  • Severe mental retardation
  • Cataracts
  • Liver damage
73
Q

What are recommendations for breastfeeding in mothers with HIV?

A
  • Breastfeeding must be done exclusively throughout six months
  • Mix-feeding is NOT recommended
74
Q

Why is breastfeeding alone not recommended for pre-term infants? What is recommended instead?

A
  • 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
75
Q

When does breast milk jaundice occur? When does it end?

A
  • Relatively uncommon (2 to 4% of infants)
  • Occurs on the fourth day of life
  • Ends on day 5 to 15
76
Q

How does breast milk jaundice develop?

A
  • 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
77
Q

What is the treatment for breast milk jaundice?

A

Phototherapy, in which a fluorescent light is absorbed by the skin of the infant, which converts the bilirubin molecules to water-soluble isomers

78
Q

Is breastfeeding recommended to be withheld in infants with breast milk jaundice?

A
  • If it is extremely severe, then yes, but only for a short period of time
  • It is not recommended in most cases
79
Q

What is the onset of eczema during breastfeeding associated with?

A
  • The blunting of growth

- Symptoms of atopic eczema and rates of growth improve after breastfeeding is discontinued

80
Q

What are possible consequences for prolonged breastfeeding beyond the age of 6 months?

A
  • Reduced growth rate

- Feeding aversion

81
Q

______ deficiency may be observed after 6 months when an infant is breastfed exclusively.

A
  • Iron

- Iron-rich foods must be introduced after 6 months, when the infant’s iron stores become depleted

82
Q

Are vitamin D supplements recommended for breastfed infants? Why or why not?

A
  • Breastfed infants may be protected from vitamin D deficiency
  • But, vitamin D supplements are recommended due to poor exposure to sunlight in Northern climates
83
Q

Which vitamin deficiency may lead to late hemorrhagic disease of the newborn?

A

Vitamin K