Chap 4 Lactation and Human Milk Part 1

7/28/2019 Chap 4 Lactation and Human Milk Part 1

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CHAPTER 4

LACTATION AND HUMAN MILKPART 1

1. The Mammary Gland

1.1 Early Development of the Breast

- Mammogenesis :

Mammary gland development begin in utero

Infant is born with a small amount of rudimentary mammary tissue. Maternal and

placental hormones near term entering the fetal bloodstream stimulate these

immature mamary gland, and newborns often secrete a thin, milklike fluid

( witches milk ) for several days after birth.

During puberty, high level of estrogen and progesterone stimulate rapid

development of the glands and growth of the breast.

During adolescence and young adulthoodm secretion of progesteron during each

menstrual cycle stimulates further growth of the mammary glands and ducts During pregnancy, final development and maturation of the breast occur,

stimulated by high levels of circulating ovarian hormones. By term, the glands are

fully formed and capable of producing breast milk to feed the newborn.

1.2 The Anatomy of the Breast

A lactiferus ( mammary )duct Enlargement (Alveoli) :

B lobules A secretory cells

C lactiferus sinus ( ampulla ) B myoepithelial cellsD nipple C ductule

E fat

F pectoralis mayor muscleG chest wall / rib cage

- Mammary gland : a compound tubuloalveolar gland embedded in a cushion of adiposetissue

- There re 15 to 20 small pores in the nipple to empty the sinuses.

- There are 15 to 20 lobes in each breast.- The average breast of an adult woman before pregnancy weigh about 150 to 200 g.


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1.3 Breast Development During Pregnancy

- Progesterone promotes an increase in the number and size of alveoli, while the ductal

system proliferates under the influence of estrogen.- The ducts and alveoli mature as prolactin and human placental lactogen (hPL) levels

sharply rise in later pregnancy.

- During the second half of pregnancy, secretory activity in the alveolar cells steadilyincreases. The alveolar cells produce a thin, yellowish liquid called colostrum and, in

the weeks before parturitionm, the alveoli become distended by accumulated

colostrum.- The mammary glands are fully mature and capable of lactation by the beginning of the

third trimester.

1.4 Birth and The early Hormonal Process of Lactation

- Prolactin stimulates the final differnetiation of alveolar cells in the breast to mature,

milk-secreting cells.

- Oxytocin, produced by the posterior portion of pituitary gland, has two major

functions postpartum :1. Oxytocin circulates to the breast and stimulates milk secretion from the alveoli

2. Oxytocin stimulates the uterus to contract which help control postpaartumbleeding and they aid in uterine involution.

2. Physiology of Lactation

Milk production : two-step process ; synthesis of milk and milk ejection or milk letdown.

2.1 Synthesis of Milk

- As the mammary glands mature during pregnancy, they become crowded with

ribosomes, endoplasmic reticulum, lipid droplets an secretory granules.- The constituens of milk are derived from :

1. Most of the components of milk are synthesized in the secretory cells of the

mammary gland, from precursors derived from the maternal bloodstream2. Some substances are produced by the other cells in the breast, passed to the

secretory cells and then secreted into the milk

3. Other components are pulled intact from the maternal plasma and transffereddirectly into the milk

- Factors that affect the composition of the plasma also influence the composition of the

milk.

- Five principal secretory pathways within the mammary epithelial cells :1. Exocytosis of Golgy-derived vesicles

Water-soluble components synthesized in ribosomes packed in Golgi

apparatus

transported to the alveolar surface

secreted by exocytosis Exocytosis e.c . lactose ( synthesized in the Golgi ); milk proteins; water-

soluble vitamins and minerals2. Apocrine secretion of milk-fat globules

Milk fat : de novo fatty acid synthesis from glucose and fatty acids taken up

from maternal plasma

Triglycerides, fatty acids and fat-soluble vitamins in lipid droplets in

mamary epithelial cells cytoplasm migrate to the cell surface pinched off

in small envelopes of cell membrane forming milk-fat globules

3. Transport through channels in the cell membrane

Ions pass through channels, carrefully regulated by the secretory cells

Water diffuses acros the alveolar cell membrane into the milk, following

the osmotic pull

Breast milk : over 90% water and isoosmotic with maternal plasma

4. Transcytosis of intact protein


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Immunoglobulin A : produced by white blood cells in the breast tissue

released into the bloodstream taken up by receptor-mediated pinocytosis

into the mammary secretory cells repackaged into secretory IgA

transffered across the secretory cell secreted into milk

5. The Pericellular Pathway

Certain situation e.g early stages of lactation, inflamation substance passingbetween loosely joined cells into the breast milk

Allows intact plasma protein e.g. albumin, electrolytes, maternal blood cells to

pass into the breast milk

2.2 Milk Ejection ( or Milk Letdown )

- The process that moves the milk from the alveoli through the ducts to the nipple so it

becomes available for the infant. Suckling by the infant initiate neuroendocrine

reflex.

- Nipple stimulation sensory nerves signals to the brain posterioir pituitary

release oxytocin

interact with myoepithelial cells sorounding the alveoli

contraction

2.3 Hormonal Control of Milk Secretion and Ejection

- Fall in progesteron high level of prolactin triggers the onset of mature milk

secretion

- Full lactation is delayed about 46 72 hours after parturition- Blood levels of prolactin 200 300 g/mL and remain elevated for 2 -3 weeks

postpartum even in women who are not breastfeeding.

- Nipple stimulation sensory nerves signals to the brain anterior pituitary releaseprolactin, posterior pituitary release oxytocin

- Prolactin : Prolactin stimulates protein synthesis and lactose formation, also increases the fat

content in the milk by stimulating lipoprotein lipase. Lipoprotein lipase increasinguptake of fatty acid from the maternal plasma and slows lipoprotein lipase activity

in adipose cells elsewhere in the body.


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Stimulates the secretory cells in the alveoli to produce milk.

Prolactin levels in the blood are doubled after 10 15 minutes of suckling.

There is rise and fall of prolactin levels proportional to the intensity and frequency

of nipple stimulation- Oxytocin :

interact with myoepithelial cells sorounding the alveoli contraction pushingmilk out into the ducts toward the nipple

- If suckling does not begun by the fourth postpartum day, milk production slows and

the milk composition reverts quickly to an immature, prepartum type; the mammary

gland involutes, connective tissue and fat gradually replace many of the alveoli.

2.4 Balancing Milk Production with Infant Demand

- If milk is not regulargly removed from the alveoli, the protein builds up and inhibit

secretion by the epitelial cells- Distension of the alveoli by accumulated milk; pressure and distension of the

secretory epithelium inhibits milk production.

3. Maturational Changes in Human Milk

- Breastmilk fundamentally is a solution of sufar, protein and salts containing a

suspesension of fat and also contains enzymes to help the newborn digest and absorbnutrients, immune factors to protect the infant from infection and hormones and growth

factors that influence infant growth

- The concentration of the individual component varies considerably from mother to

mother; even from the same woman at different stages of lactation, from day to day,diurnally and from the beginning of a single feeding to the end.

- First 2 3 weeks postpartum, milk production changes from a solution high in protein and

electrolytes and low in fat and lactose to one lower in protein and electrolytes but high in

lactose and fat.- Colostrum :

3 7 days postpartum

Thicker and more viscous, slightly yellow and not as milky as mature milk.

High concentration of carotenoids ( 10 times higher than mature milk )

Lower calories ( 58 kcal/100ml ) than mature milk ( 70 kcal/100 ml )

Principal protein : IgA protect newborn form gastrointestinal tract infection

Multiparous women produce greater volumes of colostrum than primiparous women

- Transitional Milk : milk between colostrum and mature milk

- Multiparous women often produce mature milk sooner than first-time mothers

4. Composition of Maturre Human Milk

4.1 Energy Content of Human Milk

- 58 72 kcal/100 ml ( generally 65 kcal/100ml )- 50% from fat; 40% from lacotose, 10% from protein

4.2 Lipid Content of Human Milk

- 2 5 g/100 ml ( average 4,2 g/100 ml )

- Over 95% triglycerides; small amount of phospholipids, glycolipids and FFA; 0.5%

cholesterol ( precursor for synthesis of myelin, cell membranes and steroid hormones

of the newborn )

- Lipases present in the newborn intestines and the breastmilk itself- Fat content is increased steadily during the first week post partum, then plateaus

- Fat content tends to be lowest at about 6:00 A.M.- At one feeding, the fat content is gradually increases from the beginning of the feed to

the end


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- After an average feeding, about 20% of the milk femains in the gland and this

hindmilk is particularty rich in fat.

- Multiparous women generally have less fat in the milk- Maternal nutrition can markedly affect the milk-fat concentration and the type of fats

present in the breast milk

4.3 Carbohydrate Content of Human Milk

- 7g/100 mL

- Lactose is the major carbohydrate ( 90% ), the remaining of 10 % is a variety ofmono- and oligosaccharides ( glucose, galactose, fructose adm glucosamines )

- Lactose enhance the absorption of calcium from breast milk

4.4 Protein Content of Human Milk

- 0,7 0,9 g/100ml

- Because of the high content of IgA in early milk and the immaturity of the newborns

digestive tract, up tp 10% of milk protein in the first few postpartum weeks is not

digested; by four months postpartum only about 3% of dietary protein goesunabsorbed.

- Milk-specific proteins divided into :

1. Casein Proteins

- 40% of total protein

- Linear phospoproteins, having a charged end that binds callcium, phospatesand calcium, form stable micelles

- During digestion the curd are precipitated into sizable clumps, which are

tougher and less readily digestible

2. Whey Proteins

- Alpha-lactalbumin 30%, lactoferrin 10-20% and secretory immunoglobulin A

10%

- Alpha-lactalbumin :

component of lactase synthetase ( enzyme that synthesizes lactose from

glucose and galactose )

has calcium and zinc binding sites

provide rich source of amino acids for the newborn

- Lactoferin

found only in human milk

iron-binding protein

antibacterial properties : inhibits the growth of certain iron-requiring

bacteria in the intestines

stimulus for growth and development of lymphocytes in the newborns

intestine

provide source of amino acids for growth

- Secretory immunoglobulin A

found only in human mik

synthesized from immunoglobulin A and other protein

colustrum is rich in SIgA ( 5 times higher than in mature human milk )

resist hydrolisis by enzymes and acid

blankets the epithelium of the intestine, blocking adhesion and invasion by

bacteria and viruses

The Protein Quality of Human Milk

- Rich in taurine, the second most abundant free amino acid in human milk, 30 times

that in cows milk in infant, taurine is important in bile acid metabolism and may


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function as neurotransmitter. Taurine is poorly synthesized by the newborn because

the enzyme systems arre still developing in early incancy.

- Contain only moderate amount of phenylalanine, tyrosine and methionine comparedto much higher conten in cows milk, because the enzyme systems mature late in fetal

life.

4.5 Nonprotein Nitrogen Content of Human Milk

- N-acetyl glucosamine : promote the growth of Lactobacillus bifidus in the colon

- Carnitine : essential in the oxidation of fatty acids for energy- Small amounts of free amino acids, peptides and urea but not significantly contribute

to nutritional needs.

4.6 Vitamin Content of Human Milk

Fat-Soluble Vitamins in Human Milk

- Vitamin A

200 g/100 ml ( first week postpartum ) 40 - 60 g/100 ml after several months

90% as retinyl esters in the milk-fat globules hydrolyzed by lipases in intestinaltract

Smaller amounts of retinol and beta-carotene retinol is absorbed

Beta caroten : - stored in developing mammary gland

- secreted into colustrum 34 750 g/100 ml, in mature milk 10

30 g/100 ml- Vitamin D

0,05 0,15 g/100 ml

75% is 25-OH vitamin D

- Vitamin E

0,8 1 mg/100ml ( in colostrum ) and 0,2 0,3 mg/100 ml ( in mature milk )

Mixture of several tocopherols, alpha-tocopherol 83% of total

- Vitamin K

0,2 g/100 ml in mature milk

Vitamin K synthesized by intestinal bacteria contributes to the needs during later

infancy, in the newborn the intestine is sterile it is recommended that all infants

receive supplementation of vitamin K during the newborn period

Recommended intake of 12 g/day.

Water- Soluble Vitamins in Human Milk

- Vitamin C

4-6 mg/100 ml

10 times higher that in maternal plasma

- Thiamin

1-2 g/100 ml in colostrum, seven ten fold in mature milk ( with maximum

levels at 2 3 months postpartum

Varies considerably over the course of lactation and between individual woman

- Riboflavin and Niacin

Riboflavin : 35 g/100 ml; high in colostrum and declines gradually over the

course of lactation

Niacin : 75 g/100 ml ( in colostrum ) 100-200 g/100 ml ( in mature milk

- Vitamin B6

18 g/100 ml by three weeks postpartum ( Vitamin B6 are low in colostrum andincreased markedly during first two weeks postpartum

- Folate

5 14 g/100 ml


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Bound to specific folate-binding protein in the whey fraction, in the form of

folylpolyglutamates

Folate continues to be secreted into the milk although maternal dietary intake is

low- Vitamin B12

0,03 0,32 g/100 ml Completely vegetarian women produce milk with vitamin B12 0,005 g/100 ml

- Biotin and Panthotenic Acid

Biotin : 0,6 g/100 ml and gradually increase over the course of lactation

Biotin actively secreted into breast milk at levels several hundred times greater

than the level in plasma

Panthotenic acid : 0,22 0,26 g/100 ml in mature milk, 20% higher than in

colostrum

4.7 Mineral Content of Human Milk

- Mature breast milk contains all of the essential minerals needed for infant growth anddevelopment, well-balanced and the bio-availibility for the infant is high.

- The mineral content of breast milk varies significantly with the stage of lactation.

Colostrum is richer in minerals than mature milk, and levels of many minerals contentgradually decline over the course of lactation.

- The mineral content also vary significantly during a single feeding. The calcium and

zinc levels are higher in the fore milk but the sodium and iron level are lower than thehindmilk.

- Most abundant minerals are major mineral (calcium, phosphorous, sulphur,

magnesium) and electrolytes ( pottasium, sodium and chloride ); with smaller amountof zinc, iron, chromium and copper and also trace minerals.

- Sodium, potassium and chloride concentration in colostrum are high but

concentrations in mature milk 1/3 2/3 lower than in colostrum

Major Minerals in Human Milk

- Calcium, phosphorus, magnesium bound to casein protein

- Calcium 20-35 mg/100ml

2/3 in casein micelles, 1/3 form soluble complex with citrate

highly bioavailable ( infant absorb 2/3 calcium in breast milk compare to

- 2/5 in bovine milk

Trace Minerals in Human Milk

- Iron Low in iron ( less than 0,5mg/day or 20 90 g/100 ml )

Concentrations are highest immediately after birth, level fall 20-50% from 2

weeks to 9-12 months postpartum

Level varies widely among women and from day to day in the same woman;

slightly higher in the evening than in the morning and higher in women who aremultiparous

Lactoferrin avidly binds iront and transport it in the milk

Iron in breast milk is highly bioavailable; infant absorbs 50 70% compared with

less than 10% from cows milk or formula. Ascorbic acid, lactoferrin and inosineand its metabolite increase availibility of iron

- Zinc

Concentration at 1,3,12 months postpaartum are 0,4; 0,1 and 0,05 mg/100ml

The most abundant trace element in human milk

Actively transported


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Levels in colostrum 4 5 times higher than in mature milk. Levels fall rapidly

during the first month postpartum then decline more slowly.

Theres day to day and diurnal variation

Bioavailibility is high. Picolinic acid, citrate and zinc-binding protein facilitate

zinc absorption from human milk. The absorption of the zinc given with

breastmilk was higher than with cows milk.- Copper

10 60 g/100 ml

20 30% higher in colostrum than in mature milk, level declines gradually over

the first 4 months of lactation then stable up to12 months

- Manganese

0,6 0,3 g/100 ml from first month to third month of lactation

- Selenium

1- 3 g/100 ml

Primarily bound to casein and other proteins Concentrations are highest in colostrum and decline over the course of lactation;

varies with geographic location and selenium content of the diet.

Levels in milk are directly related to maternal plasma levels, with values in milk

generaly 5 7 times those in maternal plasma.

Glutathione peroxidase, a selenium-containing enzyme, is present in milk and may

help protect the milk from oxidative damage. The activity of the enzyme in milk is

positively correlated with the selenium content of the milk.

- Iodine

Iodine metabolims during lactation is unique : the mammary gland acidly

accumulates iodine

Iodine concentration in milk : 20 30 times higher than in maternal plasma

Levels in milk are strongly correlated with maternal intake of iodine form the diet.

4.8 Digestive Enzymes in Human Milk

The digestive enzymes help the immature gastrointestinal tract of the newborn digest and

absorb nutrients in the milk.

Lipase

Mammary epithelium synthesized several lipases in inactive form contact with bile

salts in the upper intestine of the newborn become active( bile-salt stimulated lipases )

augement the activity of infant pancreatic lipase act on milk-fat globules, breaking

down triglycerides and retinyl esters; increase the absorption of fatty acids, glycerol andretinol

Amylases and Proteases

- Infant pancreatin amylase activity is low

- Mammary cells secrete amylase into milk (resistant to proteolysis in newborn

stomach) passes into small intestine aids the digestion of nonlactose

carbohydrates in milk.

- Breast milk proteases aid protein digestion in the infant intestine

4.9 Anti-Infective Factors in Human Milk

Anti-infective factors produced throughout lactation, particularly abundant in colostrum;

resistant to digestion; and protect the newborn from disesase particularly gastrointestinaldisease.

Immune Cells

- Several types of white blood cells, particularly in the early stages of lactation, foundin human milk


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- 90% are phagocytic cells, the reminder are lymphocytes ( produce antibodies,

lysozyme, lactoferrin and complement )

Immunoglobulins

- Maternal exposure to antigen maternal lymph nodes production of white blood

cells that synthesize antibodie to the antigen antibodies are produced by the white

blood cells in the mammary gland transferred into milk provide passiveimmunity, temporarily protecting infant while its own immune system matures

- Major immunoglobulin is Secretory immunoglobulin A ( SigA ) with small amounts

of IgG and IgM

Lactoferin

- Transportin iron in milk

- Also has protective effects against bacteria and viruses (antiviral activity) in thedigestive tract

- Lactoferrin complexing with iron inhibits growth of certain bacteria

Lysozyme

- Present in large amount through out lactation

- Breaks down the cell walls of pathogenic microbes- Potent antibacterial factor

Nonlactose Carbohydrates

- Glucoasamine promote the growth ofLactobacillus bifidus in the lower intestinal tract

- Lactobacillus :

dominant bacteria in the colon during infancy

break down lactose to acetic acid and other metabolites that inhibit the growth of

pathogenic bacteria

- A variety of moderate chain-length oligosaccharides are present in small amount

many have anti-infective properties, preventing the attachement of pathogenic bacteriain the intestine and neutralizing toxins secreted by certain bacteria.

4.10 Growth Factors and Hormones in Human Milk- Several factors that promotes cell growth and differentiation called growth factors.- Growth Factors :

May stimulate growth of intestinal epithelium in the newborn

May strengthen the integrity of mucosal barrier

May promote growth, differentiation, and repair in the mammary gland

during lactation- Cortisol, insulin and thyroid hormones also present in small amount in milk, their

functional significance is uncertain.

5. Contaminant in Human Milk5.1 Pesticides, Chemicals and Heavy Metals

- There is little information available on their pottential short or long-term effect on

infant health.- Major chemical contamints are pesticides e.g. DDT, organohalogen componds

including dioxin, polybrominated biphenyls (PBBs), polychlorinated biphenyls

(PCBs).- Levels of pesticides in human milk tend to be higher than in cows milk

- Trace amounts of other chemicals have been indentified in milk e.g. cyclic

hydrocarbons, halocarbons and others.- Usually only trace amounts of heave metals find their way into human milk. Level in

human milk tend to be much lower than levels in water or cows milk.

- Infant poisoning from lead transferred through breast milk has been reported, although

maternal exposure must be high for this to occur ( greater than 40 mg/dL )

5.2 Radioactivity


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- In 1986, after an explosion at the Chernobyl nuclear power plant in Russia, there were

increase levels of radioactivity found in breastmilk samples from women throughout

Europe, but the amounts were very small.- Pregnant women and lactating women were advised to avoid food from cows milk

and leagy vegetables as the levels of radioacitvity increased markedly.

- In reports from Italy, Austria, Norway and Sweden scientist concluded thatconcentrations of radioactivity were so low they didi not pose a threat to nursing

infant.

5.3 Viruses and Bacteria

- Ordinarily, human milk provides substantial immunologycal protection

- However, if the nursing mother has certain serious infection, viruses and bacteria can

be transmitted to the infant in the breast milk e.g. TBC, hepatitis B, herpes simplex ,

HIV

6. Milk Volume6.1 Measuring Milk Output

- Primary stimulus for milk production is extraction of milk from the breast by thesuckling infant, once lactation is establish

- The mammary gland carefully balances production with the infant demand.

- The most commonly used method of measuring milk intake and milk production : testweighing : the infant is carefully weighed before and after each feeding and the

amount of weight gained is used to determine milk intake.

6.2 Milk Output during Lactation

- Milk intake : 4 5 months : 400 1200 g/day with average 750 800 g/dayAfter solid food introduced between 4 7 months : 770 g/day at 6

months, 635 g/ day at 9 months, 445 g/ day at 12 months

- Breast feeding mothers have the potential to produce far more milk than is needed tomeet usual infant demands, e.g. twinns mother produce 2000 3000 g/day. Singel

infant moms can use breast pump to extract additional milk after feeding to increase

milk production by 20 40

7. Maternal Metabolism during Lactation

7.1 Substrates for Milk Synthesis

The metanbolism of nutrient is altered to give priority to milk production : energy andnutrients from diet and maternal stores are channeled into the mammary gland.

Lipid and Protein Metabolism

- Cholesterol and high-density lipoprotein levels tend to be higher in lactating women- Triglyceride levels are lower in lactating women

- High prolactin increase mobilization of fat from adipose tissue and directing

dietary lipids toward the mammary gland- Well-nourished women who are breast-feeding tend to have lower rates of protein

turnover and lower rates of muscle protein breakdown ( measured by urinary 3-

methylhistidine excretion

Micronutrient Metabolism

- Enchanced absorption from dietary sources.

7.2 Wei/ght Loss and Energy Expenditure

Patterns of Weight Loss during Lactation

- Milk production requires 500 650 kcal/day

- A woman who gains about 13 kg during pregnancy looses about 5 kg during delivery,

2 kg during the first week through diuresis of body water, and continue to lose weightduring lactation as most body fat accumulated during gestation is mobilized to supply

the needs of the breast-feeding infant.


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- During the first 4 6 months of lactation, most women are in negative energy

balance: 110 343 kcal/day in well-nourished women average weight loss duringfirst 6 months postpartum is 0,6 0,8 kg/month.

- For women who breast-feed past six months, weight loss continues during months 6

12 but at a slowe rate.

- Weight changes postpartum vary widely among individual.Weight Loss : Breast-feeding versus Formula Feeding

- Women, with babies who were exclusively breast-feeding, or formula feeding or

combines breast and formula feeding, lost weight in the six months after delivery.There were nonsignificant differences in weight loss or loss of body fat between the

women.

- Weight loss in postpartum period is influenced by several factor e.g. weight gainedduring pregnancy and parity.

Changes in Body Fat

- One study found that suprailiac and subscapular measurement typically decrease

during first 4 6 months postpartum body fat percentage is decreasing as fat is

mobilized to meet the energy needs of lactation.- Other study measured weight and triceps skinfold thickness for 2 years postpartum.

The study found that women who breastfed for at least 12 months had weight loss andloss in skinfold thickness significantly greater than women who breastfed for less than

3 months.

- In lactating women, fat is more readily mobilized from femoral adipose tissue ( hipsand thighs ) than in nonlactating women.

Energy Expenditure during Lactation

- Women who are significantly overweight can lose up to 2 kg per month without

adversely affecting lactation, but more rapid weight loss can reduce a mothers abilityto produce adequate milk..

- All lactating mother should maintain adequate daily energy intake : minimum 1500calories daily; avoid strict diets and weight loss medications- In USA total energy expenditure of lactating women not including milk production is

1800 1900 kcal/ day compared to 2200 kcal/ day for light moderately active

nonlactating women.- Enery sparing adaptation : lower basal metabolic rates, reduced thermic effect of

food small reduction in daily energy expenditure.

8. Dietary Surveys of lactating Mothers

- Data for well nourished, college-educated and Caucasioan women indicated that the

energy intakes are often below recommended amount but the intake of protein,

calcium, iron, vitamin A and C, thiaminm riboflavin and niacin to be at least 80% of

the RDAs for lactation or even exceed the RDAs.- Little information is available on the intake of lactating women from other

socioeconomic levels or minority group. Data indicate dietary intakes may be

suboptimal. The nutrient which was most likely to be low were vitamin A,D,E and C,calcium, magnesium and iron, zinc.

9. Maternal Nutritional Needs During Lactation

9.1 Nutritional Demands of Lactation

- Healthy infant doubles its weight in the first 4 6 months, all the energy, protein

and micronutrient provided by the mother.- Maternal needs duriing breast-feeding are typically higher than in any other period of

a womans life, even during pregnancy- Factor determines : the volume and composition of m ilk produced, maternal

nutritiion status when beginning lactation, underlying maternal needs.

9.2 Recommended Dietary Allowance for Lactating Woman

- Divided into recommendation for 0 6 months and 6 12 months postpartum


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- The differences reflect the difference in milk production : estimated to be 750 ml/day

for 0 6 months and 600 ml/day for 6 -12 months

9.3 RDAs for Energy

- Conversion of maternal energy into milk is estimated to be 85% efficient..

- 85 kcal for every 100 ml of milk roduced extra 640 kcal/day for first 6 months and

510 kcal/day for the second 6 months of lactation- Energy supplied by fat stores during pregnancy 2-3kg adipose tissue of a woman

who gain 12 kg during gestation could povide 100-150kcal/day during 6 months

RDA call for extra 500 kcal/day throughout lactation woman who have not gainsufficient weight during prengancy, thin, should consume additional 650 kcal druing

first six months of lactation

9.4 RDA for Protein

- Conversion of maternal protein into milk is estimated to be 70% efficient protein

requirement : 15 g/ day for the first six months and 12g/ day thereafter.

9.5 RDAs for Fat-Soluble Vitamins

- Vitamin A : 500 RE for first six months, and 400 RE for 6 12 months postpartum

maternal liver conntain about 200mg of stored vitamin A if all theextra vitamin A from breast milk come from maternal stores, six

months of breast-feeding would deplete liver stores about 25 50 %- Vitamin D : 10 g/day to maintain calcium balance

- Vitamin E : 4 mg for the first six months and 3 mg thereafter

- Vitamin K : no addiitional is recommended during lactation in US

9.6 RDAs for Water-Soluble Vitamins

- Vitamin C : daily increment 35 mg for the first six months and 30 mg for the second

six months- Thiamin : 1,6 mg

- Niacin : 20 mg

- Riboflavin : 1,8 mg during the firs six months and 1,7 during the second six months- Vitamin B6 : 0,016 mg per extra gram of protein 2,1 mg/day

- Folate : 280 g/day for the first six months and 260 g/day for the second six months

400 g/day to prevent neural tube defects

- Vitamin B12 : 0,6 g/day

9.7 RDAs for Major Minerals

- Calcium and phosporus : 1200 mg/day

- Magnesium : 75 mg/day during the first six months and 60 mg/day during the secondsix months

9.8 RDAs for Trace Minerals

- Iron : for lactating women who resume their menses : 0,5 mg/ day

- Zinc : 7 mg/ day during first six months and 4 mg/day during second six months- Selenium : 20 g/day

- Iodine : 200 g/day

9.9 RDA for water

650 ml extra fluid each day during fist six months and 530 ml thereafter

9.10 RDAs for Electrolytes

Although increase, requirement of sodium and pottasium easily met by current adultintakes. Therefore no additional intake of these electrolytes is recommended.

Chap 4 Lactation and Human Milk Part 1

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