7) Breast Milk Composition (Part II) Flashcards Preview

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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.



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.



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