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How much milk fat is in breast milk?
2.9-5.5% of milk by weight?
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What is the main component of milk fat?
98% of milk fat is in the form of triacylglycerols
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Other than TAGs, what is the rest of milk fat?
- Diacylglycerols
- Monoacylglycerols
- Cholesterol, Cholesterol esters
- FFA
- Phospholipids
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How are lipids found in breast milk?
- Enclosed within membrane-enclosed milk fat globules
- Core: TAG
- Membranes: phospholipids, cholesterol and proteins
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Wat is the main energy source of milk?
Triacylglycerols (50-60% of energy)
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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
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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
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Why is CHO not good for creating fat deposits?
CHO is only synthesized into non-essential fatty acids
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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
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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
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What happens in the maternal adipose tissue during lactation?
- Decreased lipoprotein lipase activity
- Channels FA uptake from diet and internal stores into mammary tissue
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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
- DHA
- Arachidonic acid
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What happens to TAGs in the GI tract?
TAGs + lipase--> 2-MAGs + FFA
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Why does human milk have better lipolytic activity?
- Lipoprotein lipase
- Bile salt stimulated lipases
- Pancreatic lik lipases
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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
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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
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Why are saturated fats not good in terms of absorption?
Form complexes= insoluble soaps with Ca and Mg which decreases absorption
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How does human milk improve fat absorption?
- Lipoprotein lipase from maternal serum
- Bile salt stimulated lipases
- Pancreatic like lipases
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Which has a higher cholesterol content, human milk or bovine?
Human milk as 2x higher [cholesterol] than cows milk
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Why is a higher oleic acid content in human milk good?
Oleic acid is better absorbed than saturated fat
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How do saturated fatty acids inhibit calcium absorption?
- Form Ca soaps which are insoluble in alkaline pH, making them non-absorbable
- Inhibits Ca absorption
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How can one increase DHA in breast milk?
Increase fish intake
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How much DHA is in breast milk?
0.1-0.3%
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How much DHA is in infant formula or cows milk?
negligible amounts
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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
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What happens if an infant is deficient in DHA?
Impaired vision and learning
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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
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What happens when infants are fed excess eicosapentanoic acid?
Decrease RBC phosphoplipid content of arachadonic acid- associated with decreased growth
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Does linolenic acid increase DHA levels?
Linolenic acid addition alone does not seem to optimally increase DHA in RBC phospholipids
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What is the least variable component in breast milk?
- Lactose
- Exerts 60-70% of osmotic pressure of milk
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How does the mothers diet influence lactose concentration in breast milk?
No influence on milk [lactose]
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Why is lactose important in breast milk?
Aids in mineral absorption by forming soluble chelates with minerals?
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Why is lactose important in GI health?
Stimulates beneficial microorganisms in gut
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What component in breast milk aids lactose digestion?
Amylast in breast milk aids in lactose digestion
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Why is the osmotic pressure of milk important?
Lactose contribution to osmotic pressure --> milk isoosmotic to plasma --> low energy cost to maintain osmolarity
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What are the advantages of human milk vs bovine in terms of nutrient content?
- Better mineral bioavailability
- Better Ca:P ratio
- Lower solute load
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Why is Ca and Zn bioavailability increased in human milk?
Lactalbumin: metalloenzyme; binds Ca and Zn
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Why is Fe and Mo bioavailability increase in human milk?
Xanthine oxidase
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Why is Se bioavailability increase in human milk?
Glutathione peroxidase is Se carrier
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Why is Fe bioavailability increased in human milk?
Lactoferrin: Fe is highly bioavailable
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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
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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
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What is preterm milk?
- Higher energy, protein, Na and Cl
- Lower lactose
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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
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Why should preterm milk be fortified?
Insufficient in Ca, P, Mg, vit.D
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Why does preterm milk have higher protein and higher energy?
Preterm infants need rapid growth rate approximating in utero growth
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How does foremilk differ from hindmilk?
- Foremilk is low in fat
- Hindmilk has a 3x increase in milk fat content
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What is milkfat content influenced by?
Milk fat content is influenced by length of time between feedings, timing of nursing
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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)
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What type of fats are needed for myelin sheath synthesis?
MCFA
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How does malnutrition affect breast milk composition?
- Does not seem to affect the immune factors in mature milk
- Immune factors are decreased in colostrum
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How does protein deficiency affect breast milk composition?
- Milk protein content is not easily affected by malnutrition
- Unless prolonged and severe protein calorie malnutrition
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What factor affects milk volume?
Only severe malnutrition will hinder milk volume
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How does maternal body fat content effect milk fat?
Increase in maternal fat content--> increase milk [fat]
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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
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How is cholesterol and phospholipid content of milk affected by diet?
Cholesterol and phospholipid content is unaffected
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What factor can increase milk cholesterol content?
Increase milk cholesterol content only in severe hypercholesterolemia
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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
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What affects linoleic acid content in breast milk?
Diet (vegetarians have 30% linoleic acid)
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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
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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
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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)
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Which fat soluble vitamin is affected buy maternal diet?
Vitamin D decreases with decreased sun exposure decreased dietary intake
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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
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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
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When is infantile beri-beri seen?
After child is nursed by mother with beri-beri
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How is folate in milk affected?
Folate milk content is unaffected by deficiencies in the mother
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What happens if a mother has low B6 intake?
- Increased risk of B6 deficiency in the infant
- Decreased attentiveness
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What happens if a mother is low in vitamin C?
Decreased milk vitamin C content
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Can maternal supplementation of water soluble vitamins cause overdose?
Maternal supplementation of water soluble vitamins causes an increase until a plateau is reached
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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
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How is iodine effected in breast milk?
Excess maternal intake (60% from salt, 25% from dairy) especially from milk leads to excess breast milk
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What are some disadvantages to breastfeeding?
- Environmental contaminants
- Heavy metals and pesticides present in breast milk
- Vitamin K deficiency
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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
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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)
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How do dioxins and PCBs enter breast milk?
Breast milk source of PCBs and dioxins predominantly from stored levels in maternal adipose tissue
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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
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How does low vitamin K affect neonates?
- Developmental immaturity to synthesize prothrombin
- Low prothrombin levels (20% of adult values) 1-7 days postpartum
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Which vitamin is breast milk particularly low in?
Vitamin K
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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
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Why do newborns not make their own vitamin K?
Have a sterile gut -> No bacterial contribution to vitamin K intake
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What is done to combat vitamin K deficiency in newborns?
Vitamin K injections are given at birth
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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
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What are two important factors when determining wether a drug is safe to use during breastfeeding?
Dose and duration
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How do hallucinogenic drugs affect infants?
Irritability, tremors, withdrawal symptoms in infants
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What happens if a mother is taking anticonvulsants?
Infant may need vitamin K supplements
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What can happen to the infant if the mother is taking oral contraceptives?
- Cause gynecomastia (enlarged breasts) in young infants
- Suppress lactatiom
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How do antibiotics taken by the mother affect the infant?
Allergic reactions, sleepiness, vomiting and refusal to eat
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How does caffeine taken by the mother affect the infant?
1-2 cups/day = restlessness, irratbility and sleeplessess in the infant
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Why is caffeine so dangerous for infants?
Caffeine accumulates in the infant over time; may interfere with Fe availability and status in the infant
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How do sedatives taken by the mother affect infants?
Cause lethargy in infants
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How does smoking affect lactating mothers?
Decreases milk volume
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How do hot spices and garlic affect lactating mothers?
Cause distress in infant
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How does alcohol affect breastfeeding infants?
- Decrease infants intake of milk
- Decrease milk production
- Readily enters breast milk
- Peaks in milk 1h after intake
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How does exercise affect breast milk?
Intense exercise builds up lactic acid which increases acidity in breast milk
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What is lofenalac?
An infant formula with low PHE content?
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When is lofenalac used?
Used in infants with phenylketonuria because it has a low PHE content
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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
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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.
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What is breast milk lacking for premature infants?
Insufficient Ca and P for skeletal growth
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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
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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
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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
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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
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Why are Fe supplements in infants controversial?
Fe deficiency is less common in breast fed infants
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Why are vitamin D supplements recommended for breastfeeding women?
Due to generally poor exposure to sunlight in Northern Climates
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