How much milk fat is in breast milk?
2.9-5.5% of milk by weight?
What is the main component of milk fat?
98% of milk fat is in the form of triacylglycerols
Other than TAGs, what is the rest of milk fat?
- Cholesterol, Cholesterol esters
How are lipids found in breast milk?
- Enclosed within membrane-enclosed milk fat globules
- Core: TAG
- Membranes: phospholipids, cholesterol and proteins
Wat is the main energy source of milk?
Triacylglycerols (50-60% of energy)
How much fat do infants need to deposit in the first 6 months?
Infants need to deposit 1.4-1.7 kg of fat in the 1st 6 months
Why is dietary fat of such high importance to infants?
- Dietary fat converted to adipose tissue more efficiently than CHO or proteins
- Low osmotic or metabolic cost- 1% of energy ofd absorbed TAG invested for cost of adipose tissue vs 25% for CHO
Why is CHO not good for creating fat deposits?
CHO is only synthesized into non-essential fatty acids
Where are milk fatty acids synthesized?
- if <16C: synthesized in the alveolar cells within the mammary gland from glucose
- if >18C: come from maternal adipose stores and diet
What happens as a result of increased prolactin production just preceding and during lactation?
- Increased lipoprotein lipase activity in the mammary gland
- Increased FFA uptake into the mammary gland
What happens in the maternal adipose tissue during lactation?
- Decreased lipoprotein lipase activity
- Channels FA uptake from diet and internal stores into mammary tissue
What are the advantages of human vs bovine milk in terms of fat absorption and composition?
- Higher proportion of Palmitate at 2-position of TAGs
- Better lipolytic activity
- Higher oleic and lower saturated fatty acid content
- 5x greater EDFA content than cows milk
- Linolenic acid
- Long-chain fatty acids, free fatty acids
- Arachidonic acid
What happens to TAGs in the GI tract?
TAGs + lipase--> 2-MAGs + FFA
Why does human milk have better lipolytic activity?
- Lipoprotein lipase
- Bile salt stimulated lipases
- Pancreatic lik lipases
Why is it better to have palmitate at 2-position of TAGs?
- Advantage in terms of absorption
- MAGs with palmitic acid are much better absorbed than free palmitic acid
Why are MAGs important in terms of absorption?
- Form better micelles with bile salts than free palmitic acid
- Lower melting point (need lower [bile salts] to emulsify into micellar form
Why are saturated fats not good in terms of absorption?
Form complexes= insoluble soaps with Ca and Mg which decreases absorption
How does human milk improve fat absorption?
- Lipoprotein lipase from maternal serum
- Bile salt stimulated lipases
- Pancreatic like lipases
Which has a higher cholesterol content, human milk or bovine?
Human milk as 2x higher [cholesterol] than cows milk
Why is a higher oleic acid content in human milk good?
Oleic acid is better absorbed than saturated fat
How do saturated fatty acids inhibit calcium absorption?
- Form Ca soaps which are insoluble in alkaline pH, making them non-absorbable
- Inhibits Ca absorption
How can one increase DHA in breast milk?
Increase fish intake
How much DHA is in breast milk?
How much DHA is in infant formula or cows milk?
Why is DHA important in the first 18 months of life?
- Predominant EFA in retinal phospholipids
- Large amounts deposited in brain cell membranes in first 18 months of life
What happens if an infant is deficient in DHA?
Impaired vision and learning
Why are EFA precursors importnat in infants, especially premature infants?
- EFA precursors (linoleic and linolenic acids) may not be sufficient (especially in premature infants)
- Immaturity of elongase and desaturase enzymes to synthesize sufficient LCFA for optimal growth and CNS needs
What happens when infants are fed excess eicosapentanoic acid?
Decrease RBC phosphoplipid content of arachadonic acid- associated with decreased growth
Does linolenic acid increase DHA levels?
Linolenic acid addition alone does not seem to optimally increase DHA in RBC phospholipids
What is the least variable component in breast milk?
- Exerts 60-70% of osmotic pressure of milk
How does the mothers diet influence lactose concentration in breast milk?
No influence on milk [lactose]
Why is lactose important in breast milk?
Aids in mineral absorption by forming soluble chelates with minerals?
Why is lactose important in GI health?
Stimulates beneficial microorganisms in gut
What component in breast milk aids lactose digestion?
Amylast in breast milk aids in lactose digestion
Why is the osmotic pressure of milk important?
Lactose contribution to osmotic pressure --> milk isoosmotic to plasma --> low energy cost to maintain osmolarity
What are the advantages of human milk vs bovine in terms of nutrient content?
- Better mineral bioavailability
- Better Ca:P ratio
- Lower solute load
Why is Ca and Zn bioavailability increased in human milk?
Lactalbumin: metalloenzyme; binds Ca and Zn
Why is Fe and Mo bioavailability increase in human milk?
Why is Se bioavailability increase in human milk?
Glutathione peroxidase is Se carrier
Why is Fe bioavailability increased in human milk?
Lactoferrin: Fe is highly bioavailable
Why is a better Ca:P ratio in breast milk important?
Excess P relative to Ca --> increased gut excretion of Ca --> less Ca excretion in gut with breast milk
Why is a lower solute load of human milk good?
Lower solute load--> less stress on infants kidneys when combined with the lesser protein content of human breast milk
What is preterm milk?
- Higher energy, protein, Na and Cl
- Lower lactose
What happens to breast milk composition with increasing gestational age?
- Decrease in total protein, Igs and Fat soluble vitamins
- Increase lactose, fat, energy and water soluble vitamins
Why should preterm milk be fortified?
Insufficient in Ca, P, Mg, vit.D
Why does preterm milk have higher protein and higher energy?
Preterm infants need rapid growth rate approximating in utero growth
How does foremilk differ from hindmilk?
- Foremilk is low in fat
- Hindmilk has a 3x increase in milk fat content
What is milkfat content influenced by?
Milk fat content is influenced by length of time between feedings, timing of nursing
Why is there in increase proportion of SFA in mature milk?
- Less contribution from dietary and maternal stores
- Changing needs of infant: decreased rate of nerve cell division; myelination rate increases (need MCFA synthesized by mammary gland for myelin sheath synthesis)
What type of fats are needed for myelin sheath synthesis?
How does malnutrition affect breast milk composition?
- Does not seem to affect the immune factors in mature milk
- Immune factors are decreased in colostrum
How does protein deficiency affect breast milk composition?
- Milk protein content is not easily affected by malnutrition
- Unless prolonged and severe protein calorie malnutrition
What factor affects milk volume?
Only severe malnutrition will hinder milk volume
How does maternal body fat content effect milk fat?
Increase in maternal fat content--> increase milk [fat]
What happens to breast milk if insufficient maternal fat reserves are put on during pregnancy?
Fat content of breast milk can decrease significantly to 1g/100ml
How is cholesterol and phospholipid content of milk affected by diet?
Cholesterol and phospholipid content is unaffected
What factor can increase milk cholesterol content?
Increase milk cholesterol content only in severe hypercholesterolemia
What factor effects the secretion of cholesterol and phospholipids?
Integral components of the milk fat globule; their secretion rates correspond to the total quantity of milk fat secretion
What affects linoleic acid content in breast milk?
Diet (vegetarians have 30% linoleic acid)
What happens if an infants linoleic acid intake is low?
If infants intake of linoleic acid <6% of total fat, increased risk of EFA deficiency
What happens if the mother has an energy restricted diet?
- Increased proportion of C16
- Saturated LCFA predominant
- Indicates that stored fat is used for fat synthesis
What happens to vegan infants?
- Insufficient DHA (decreased n-3 FA intakes and reserves in vegan mothers)
- High intakes of AA (high intake of linoleic acid in vegan mothers)
Which fat soluble vitamin is affected buy maternal diet?
Vitamin D decreases with decreased sun exposure decreased dietary intake
What can happen if a mother supplements with vitamin D?
- Maternal supplementation of vit D can cause toxicity in the infant
- Excess goes into milk-> hypercalcemia
- Failure to thrive, vomiting, constipation, anorexia
How are water soluble vitamins affected by maternal nutrition?
- Water soluble vitamins are generally affected by malnutrition-> may cause deficiencies in infant
- Infantile B12 deficiency has been seen in vegetarians who breast feed
- Infantile Ber-beri is seen after being nursed by mother with beri beri
When is infantile beri-beri seen?
After child is nursed by mother with beri-beri
How is folate in milk affected?
Folate milk content is unaffected by deficiencies in the mother
What happens if a mother has low B6 intake?
- Increased risk of B6 deficiency in the infant
- Decreased attentiveness
What happens if a mother is low in vitamin C?
Decreased milk vitamin C content
Can maternal supplementation of water soluble vitamins cause overdose?
Maternal supplementation of water soluble vitamins causes an increase until a plateau is reached
How are minerals effected in breast milk?
- In general, no significant relationship between maternal intake and breast milk content
- Major minerals, trace elements: maintained as constants over a wide range of intakes
- Exceptions: Se, I
How is iodine effected in breast milk?
Excess maternal intake (60% from salt, 25% from dairy) especially from milk leads to excess breast milk
What are some disadvantages to breastfeeding?
- Environmental contaminants
- Heavy metals and pesticides present in breast milk
- Vitamin K deficiency
Why are environmental contaminants more detrimental to fetuses than infants?
Fetuses have more sensitive CNS, higher dose per kg body weight and less fat tissue to store contaminants
How do dioxins and PCBs affect infants?
May interfere with vit K metabolism; may contribute to late hemorrhagic disease of newborn (bleeding, easy bruising, mucosal bleeding and severe intracranial hemorrhaging)
How do dioxins and PCBs enter breast milk?
Breast milk source of PCBs and dioxins predominantly from stored levels in maternal adipose tissue
How do dioxins in the maternal diet affect breast milk?
- No difference between a high dioxin diet and a low dioxin diet during lactation
- Daily intake contributes only 14% of the total excretion of dioxins in breast milk
How does low vitamin K affect neonates?
- Developmental immaturity to synthesize prothrombin
- Low prothrombin levels (20% of adult values) 1-7 days postpartum
Which vitamin is breast milk particularly low in?
How do cows milk vitamin K levels compare to those in human breast milk?
Cows milk has 4x higher content of vitamin K than human milk
Why do newborns not make their own vitamin K?
Have a sterile gut -> No bacterial contribution to vitamin K intake
What is done to combat vitamin K deficiency in newborns?
Vitamin K injections are given at birth
How do PCBs and dioxins interfere with vitamin K metabolism?
- PCBs induce microsomal Cytochromes P-450 activity
- Microsomal gamma-glutamyl carboxylase of which vitamin K is a substrate and a cofactor
- Vitamin K not recycled in the normal salvage pathway but is metabolized and excreted due to induction of cytochromes P450
- Observed with anti-convulsants and phenobarbital
What are two important factors when determining wether a drug is safe to use during breastfeeding?
Dose and duration
How do hallucinogenic drugs affect infants?
Irritability, tremors, withdrawal symptoms in infants
What happens if a mother is taking anticonvulsants?
Infant may need vitamin K supplements
What can happen to the infant if the mother is taking oral contraceptives?
- Cause gynecomastia (enlarged breasts) in young infants
- Suppress lactatiom
How do antibiotics taken by the mother affect the infant?
Allergic reactions, sleepiness, vomiting and refusal to eat
How does caffeine taken by the mother affect the infant?
1-2 cups/day = restlessness, irratbility and sleeplessess in the infant
Why is caffeine so dangerous for infants?
Caffeine accumulates in the infant over time; may interfere with Fe availability and status in the infant
How do sedatives taken by the mother affect infants?
Cause lethargy in infants
How does smoking affect lactating mothers?
Decreases milk volume
How do hot spices and garlic affect lactating mothers?
Cause distress in infant
How does alcohol affect breastfeeding infants?
- Decrease infants intake of milk
- Decrease milk production
- Readily enters breast milk
- Peaks in milk 1h after intake
How does exercise affect breast milk?
Intense exercise builds up lactic acid which increases acidity in breast milk
What is lofenalac?
An infant formula with low PHE content?
When is lofenalac used?
Used in infants with phenylketonuria because it has a low PHE content
What is galactosemia?
- Rare autosomal recessive disorder
- Galacticol, a reduced form of galactose that is highly toxic and causes severe mental retardation, cataracts and liver damage
How is glucose converted to galactose?
Galactose + ATP ----Galactose –1-P + ADP + Pi
Galactose –1-P -----UDP-Galactose + Glucose –1-P converted via 1-P uridyl transferase (deficient) --> cannot convert galactose to UDP-Galactose
- Galactose –1-P accumulates producing galactitol, a reduced form of galactose that
- is highly toxic.
What is breast milk lacking for premature infants?
Insufficient Ca and P for skeletal growth
What is breast milk jaundice?
- Uncommon (2-4% of infants)
- Starts day 4 and ends day 5-15
- Treatment: extra water, phototherapy
- If hyperbilirubinemia persists or is excessively high--> withhold milk for short period of time
What happens if breastfeeding is prolonged beyond 6 months?
Prolonged feeding of breast milk without introduction of solids beyond 6 months causes reduced growth rate and feeding aversion
How much solids should a child be eating at 6 months and 10 months?
- 6 month infant: solids provide 20% of energy intake
- For 10 month infant: solids provide 50% of energy intake
When can iron deficiency occur in infants?
- Iron deficiency may occur after 4-6 months of age if Fe rich foods are not introduced
- Not important for formula fed infants who receive Fe-fortified formula
Why are Fe supplements in infants controversial?
Fe deficiency is less common in breast fed infants
Why are vitamin D supplements recommended for breastfeeding women?
Due to generally poor exposure to sunlight in Northern Climates