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What precent of milk by weight is fat?
2.9 to 5.5%
____% of milk fat is in the form of triacylglycerides (TAGs)
Other than TAG what are the other fat components in milk?
- cholesterol esters
What is enclosed within milk fat globules?
- Core: TAG
- Membranes: PL,CH, porteins
What % of milk energy do TAG make up?
Infants need _______kg fat in the 1st 6 months
1.4 - 1.7
Fat has a low ______________________ cost. __% of energy of absorbed TAG invested for cost of adipose tissue vs. ___% for CHO
- osmotic or metabolic
Where do milk FAs of ≤16C come from?
synthesized in the aveolar cells within the mammary gland from glucose
Where do milk FAs of ≥18C come from?
maternal adipose stores and diet
Maternal Milk Lipid synthesis increased ___________ activity just preceding and during lactation leads to increased _______________ in the mammary glands leaing to increased _____ uptake into the mammary gland
- lipoprotein lipase
Maternal Milk Lipid synthesis in maternal adipose tissue decreased ________________ activity leads to __________ FA uptake from ____________________into mammary tissue
- lipoprotein lipase
- diet and internal stores
List advantages of human milk 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 SFA content
- 5x greater EFA content than cow's milk
- linolenic acid content of 0.7-1.3% in breast milk vs 1-5% in formulas
- better mineral bioavailibility
- Better Ca:P ratio
- lower solute load (Mg, Na, K, Citrate) in human breast milk
what is the primary SFA in cows milk and human milk?
TAGs + lipase --> 2 MAGs + FFA
slow hydrolysis of _____________
palmitic acid in 2 position is an advantage in terms of absorption, why?
- MAGs with palmitic acid are much netter absorbed than free palmitic acid
- MAGs from better micelles with bile salts than free palmitic acid- lower melting point
SFA, PUFA, and MUFA have lower melting points what does this mean for their emulsification?
need lower bile salt concentration to emulsify them
What decreases SFA absorption?
- SFA complex and form insoluble soaps with Ca and Mg leading to decreased absorption
- inhibit Ca absorption
- not soluble in alkaline pH --> non-absorbable
What lipases present in human breast milk improve fat absorption and lipolytic activity?
- lipoprotein lipase from maternal serum
- bile salt stimulated lipase
- pancreatic like lipase
Which has more CH human milk or cow's milk?
human milk has 2x [CH] than cow's milk
Why is higher oleic and lower SFA content better?
oleic acid is better absorbed than saturated fat
T or F- EFA is 5x greater in breast milk then cows milk but it can be higher in infant formula
- EFA in infant formula is 10-16% of energy
List the major factors that influence breast milk composition
- gestational ages
- length of lactation
- increase in maternal fat content will lead to an increase in milk fat content
- insufficient maternal fat reserves put on during pregnancy lead to fat content of breast milk going down significantly
How does malnutrition affect milk composition?
- does not seem to affect the immune factors in mature milk but immune factors in colostrum are decreased
- milk protein content is not easily affected by malnutrition unless prolonged and severe protein calorie malnutrition
- no evidence that alteration in maternal diet will affect the total milk fat content nor milk volume
- only severe malnutrition in the form of severe energy restriction will hinder milk volume
Long chain fatty acids are ______ higher in breast milk than infant formula
DHA accounts for ______% in breast milk
How can the amount be increased?
How much DHA is in formula?
- 0.1 - 0.3%
- can increase by fish intake
- negligible amounts in formula
What effects occur from DHA deficiency?
impaired vision and learning
Arachidonic acid _______% in omnivores
___________ levels are lower in formula fed infants than breast fed infants but __________ arachidonic acid content is similar in both groups
low amounts of DHA --> low EPA, how does this effect infants?
- low RBC PL content of arachidonic acid
- associated with decreased growth
What can be done to formula to improve growth and cognitives performance?
- enriching the formula with DHA only
- Linolenic acid addition alone does not seem to optimally increase DHA in RBC PL
What is the second most abundant constituent in breast milk after water? What is its total concentration?
Lactose is the least variable component in milk its exerts _______% of osmotic pressure of milk.
What does lactose's contribution to osmotic pressure result in?
- leads to milk isoosmotic to plasma
- leading to low energy cost to maintain osmolarity
- stimulates beneficial microorganisms in the gut (e.g. lactobacilli)
What is the function of amalyase in breast milk?
aids in lactose digestion
Besides contributing to osmotic pressure what is another function of Lactose in breast milk?
aids in mineral absorption by forming soluble chelates with minerals
What compounds aid in mineral bioavailability in breast milk? What mineral does each one aid in digestion?
- lactalbumin metalloenzyme binds Ca and Zn
- xanthine oxidase- Fe and Mo
- glutathione peroxidase Se carrier
- alkaline phosphataste: Zn and Mg
- lactoferrin Fe (high bioavailable form)
What is the Ca:P ratio in breast milk?
What is the Ca:P ratio in cows milk?
What effects does having a low P relative to Ca have on infants?
increased gut excretion of Ca thus less Ca is excreted in gut with breast milk
What effect does having a lower solute loas in human breast milk have on infants?
less stress on infants kidneys when combined with the lesser protein content of human breast milk
What are the characteristics of preterm milk?
- higher energy, protein, Na and Cl
- lower lactose
- insufficient in Ca, P, Mg, vit D --> milk should be fortified
Why does preterm milk have higher protein and energy?
preterm infants have a rapid growth rate approximating in utero growth
What happens to breast milk with increasing length of lactation?
- lower total protein, Ig's and fat soluble vitamins
- increased lactose, fat, energy, and water soluble vitamins
There is an increased proportion of which FAs in mature milk from colostrum? Why?
- C8:0, 10:0, 12:0, 14:0, and 16:1
- less contribution from dietary and maternal stores
- changing needs of infants: decreased rate of nerve cell division, myelination rate increases (need MCFA synthesized by mammary glands for myelin sheath synthesis)
What is milk fat content influenced by?
- length of time between feedings and time of nursing
- foremilk= low fat
- hindmilk = 3x increase in milk fat content
What result does insufficient maternal fat reserves put on during pregnancy have on breast milk?
fat content of breast milk can significantly decrease to 1.0g/100mL
What is the influence of diet on milk composition?
- CH and PL content is unaffect by changes in diet
- milk FA composition is affected by dietary fat composition
- linoleic acid content in human breast milk depends on diet
- fat soluble vitamins are not much affected by maternal malnutrition
- water soluble vitamins generally affected by malnutrition
When is milk CH content affected/changed?
milk CH is increased in severe hypercholestolemia
CH and PL are integral components of milk _____________
Their secretion rate correspond to the total quantity of ________________________
- fat globules
- milk fat secretion
What precent linoleic acid do vegetarian mothers have in their diet?
What precent linoleic acid do omnivore mothers have in their diet?
>6.9 to 18%
What precent linoleic acid do very low fat mothers have in their diet?
What are the effects of a low fat energy restricted diet on milk composition?
- increased proportion of C16
- saturated LCFA predominant
- indicates that stored fat is used for fat synthesis
What are the effects of vegan mothers on infants FA profile?
- insufficient DHA (decreased n-3 FA intakes and reserves in vegan mothers
- high intakes of arachadonic acid (high intake of linoleic acid in vegan mothers)
Which fat soluble vitamin content changes in in milk? What conditions cause it to change?
- Vit D
- decreases with decreased exposure and decreased dietary intake
- maternal supplementation can cause toxicity in the infant
What does excessive vit D in maternal milk result in?
- failure to thrive
What population has infantile B12 deficiency been observed in?
vegetarians who breast fed their infants
What population has infantile beri-beri been observed in?
in infants nursed by mother with Beri-Beri
T or F Folate milk content is affected by deficiencies in mother?
- Folate milk content is unaffected
How does low maternal B6 occur? What are the implementation for their infants?
- Low maternal B6 is associated with a protein poor diet
- This leads to an increased risk of B6 deficiency in the infant and decreased attentiveness in infants
What are the results of low maternal vitamin C intake?
decreased Vit C content in milk
Se and Id milk content is closely linked to ____________________________
maternal dietary intake
T or F maternal supplementation of water soluble vitamins will continually increase their content in milk
- they will cause an increase until a plateau is reached
In general what is the relationship between maternal dietary mineral intake and their content in milk?
no significant relationship b/w maternal intake and breast milk content
What major minerals are maintained as a constant over a wide range of intakes?
- Major minerals: Ca
- Trace minerals: Cu, Zn, Fe
What is considered excessive I intake? and what will it result in?
- 60% from salt 25% from dairy especially from milk 100 to 1300 ug/L
- leads to excessive I content in breast milk
What are the disadvantages to breast feeding?
- environmental contaminants
- vit K deficiency
- HIV infection
- premature infants require fortified breast milk
- breast milk jaundice
- development of moderate to severe eczema due to breast milk allergy
Why may the risk of environmental contaminants be greater for the fetus then breast fed infants?
fetuses have more sensitive CNS, higher does per kg body weight and less fat tissue to store contaminants
What are the implications of heavy metals and pesticides in breast milk?
does not seem to be toxicologically siginifcant quantities except in the case of an environmental catastrophe (Minamata Bay, Japan --> Hg into water supply --> severe neurological disordered)
What implications do dioxins and PCBs have on the newborn?
suggested that dioxins and PCBs may interfere with vit. K metabolism; may contribute to late hemorrhagic disease of new borns (bleeding, easy bruising, mucosal bleeding and severe intracranial hemorrhaging)
When are PCBs and dioxins excreted in higher amounts?
1st week after birth
What is the source of PCBs and dioxins?
- from stored levels in maternal adipose tissue
- no difference b/w a high dioxin diet and low dioxin diet during lactation
- daily intake contributes only 14% of the total excretion of dioxins in breast milk
Breast milk is low in vit K, what effects could this have on new borns?
- late hemorrhagic disease of newborns
- developmental immaturity to synthesized prothrombin
- low prothrombin levels (20% of adult values) 1-7 days postpardum
- newborns have sterile gut- no bacterial contribution to vit K intake
- poor Vit K stores at birth
How much more Vit K is there in cows milk than breast milk?
What is done to help infant vit K status?
- it is injected after birth
- i.m. injection (0.5-1mg dose)
- required by law
- this lead to an increase of late hemorrhagic disease
How do PCB interfere with vit K metabolism?
- PCBs induce microsomal cytochromes P-450 activity leading to microsomal gamma-glutamyl carboxylase of which Vit K is a substrate and a cofactor
- vitamin K is not recycled in the normal salvage pathway but is metabolize and excreted due to induction of Cytochromes P450
- observed with anti convulsants and phenobarbital
LHD is ___ times higher in Japan than in western countries
Why is this?
- 2 times higher
- in Japan increase in fish consumption lead to an increase in PCB thus a higher rate of LHD
Most commonly used drugs are excreted into milk but only a handful pose a significant health risk. What characteristics are desirable for drugs taken while breast feeding?
- drugs with short half life cleared from system between feedings
- drugs less readily excretable in milk
Dose and duration of drug use are important regarding their effect on breast milk. What are the effects of chronic asprin that dont occur with just one dose.
rashes, acidosis, and altered platelet function
What are the effects of hallucinogenic drugs such as heroin and cocaine on infants?
- withdrawal symptoms in infants
What is a side affect for the infant of a mother taking anti-convulsants?
infants need supplementation of Vit K
What are some side effects of a lactating mother taking oral contraceptives?
- gynecomastia (enlarged breasts) in young infants
- suppress lactation
What are some side effects of a lactating mother taking antibiotics?
- allergic reactions
- refusal to eat
What are the effects of 1-2 cups caffeine a day on infants
- accumulates in infants over time
- may interfere with Fe availability and status in infant
What are some side effects of a lactating mother taking seditives?
lethargy in infants
What are some side effects of a lactating mother smoking?
- decreased milk volume
- less weight gain in infants
- associated with SIDS (sudden infant death syndrome)
What are some side effects of a lactating mother consuming hot spices and garlic?
- distress in infant
- alteration of the milk flavor
What are some side effects of a lactating mother consuming alcohol?
- decreased infant milk intake
- decreased milk production
What are some side effects of a lactating mother exercising?
- compatible with breast feeding
- intense exercise leads to lactic acid which leads to increased acidity in breast milk
What is PKU?
- an autosomal recessive metabolic genetic disorder
- enzyme phenylalanine hydroxylase (PAH) is non-functional
- PHA is necessary to metabolize phenylalanine and tyrosine
- phenylalanine accumulates and is converted to phenylpyruvate which is detected in urine
How is PKU dectected and treated in infants? What happens if it is not treated?
- infants screened at birth with a number of other inborn errors of metabolism
- Lafenalac is preferred source of infant formula with low PHE content
- otherwise infants will get severe mental retardation
What is galactosemia?
- a rare autosomal recessive disorder
- occurs in 1/60,000
- inability to metabolize galactose sugar produced from lactose
- galactitol, a reduced form of galactose that is highly toxic and causes severe mental retardation, cataracts and liver damage
How is galactitol produced in people with galactosemia?
- 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
should women with HIV breast feed?
it is not recommended except in developing countries since there have been 1.5 million deaths/ year due to poor sterilization of drinking water
How many people do not have enough safe drinking water?
1.2 billion people
Why do premature infants require fortified breast milk?
breast milk is insufficient in Ca and P for skeletal growth
How often does breast milk jaundice occur? How long does it last? Why does it occur? How is it treated
- uncommon 2-4% of infants
- starts day 4 and ends day 5-15
- metabolite of progesterone, pregnane-3-α-20-β-diol; inhibits bilirubin conjugated by glucoronyl transferase
- treatment is extra water, phototherapy
- if hyperbilirubinemia persists or is excessively high-> withhold milk for short period of time
What does a baby getting eczema while breast feeding indicate?
- onset of allergies associated with blunting of growth
- after breastfeeding was discontinued symtoms of atopic eczema improved as did rates of growth
What are the effects of prolonged feeding of breast milk without introduction of solids beyond 6 months.
- reduced growth rate
- feeding adversion
What precent of energy should solids account for in a 6 month old infant and a 10 month old infant?
- 20% at 6 months
- 50% at 10 months
Iron deficiencies may occur after _____months of age if Fe rich foods are not introduced
T or F formulas are fortified with Fe
T or F It is agreed upon that breast fed infants should receive Fe supplementation
- it is controversial as Fe deficiency is less common in breastfed infants
How much Vit D should breast fed infants be supplemented? Why?
- recommended due to generally poor exposure to sunlight in Northern climates even though breast fed infants are more protected from Vit D deficiency