Human Breast MIlk

 

Human milk is the best food for newborn.

There is no ideal alternative composition for human milk which can be as complex in composition as breast milk and never create the whole child mother bonding unique to the process of breast feeding.

Breast milk is extremely complex and highly variable biofluid that has evolved over the millenium

Some terminologies

EBF - Only breast milk and not even water

Predominant breast feeding - Small amount of other food,water but predominantly fed breast milk

Partial BF - Some breast feeding and some other feeds

Token breast feeding - Mostly other feeds and sometime breast feeds

Bottle-feeding - feeding from bottle even if the feed is expressed breast milk

What is the composition of human breast milk?

Human milk is composed of 87% of water, 4% fat, 7% carbohydrate and 1 % protein.

Fat and carbohydrate form 50 and 40% of total energy sources.

In addition to that mother's milk is composed of lots of other vitamins and minerals.

What is foremilk & hindmilk?

The milk that is expressed first (foremilk) is thinner with a higher content of lactose, which satisfies a baby’s thirst, and following the foremilk, hindmilk, is creamier with a much higher content of fat for the baby’s needs and hunger.

What is the lipid content of maternal milk?

Largest source of energy for newborn present in emulsified form.

Milk fat is the carrier of aroma and taste

Triglycerides is the main lipid in milk which is 98% of total lipids.

Long chain polyunsaturated fatty acid (LC-PUFA) comprises of 2% of tota llpids in milk.

LC-PUFA like ω6 (such as arachidonic acid) and ω3 (such as eicosapentaenoic and docosahexaenoic acids [DHA]), which are derived from essential fatty acids: linoleic and α-linolenic acid are important for the brain development of the infant.

Similarly cholesterol in breast milk is a precursor of hormones and also involved in brain development.

What is the role of PUFAs in human milk?

Cell differentiation and formation of synapses

Also in vision

Anti-inflammation and immune upregulation

When does the newborn acquire PUFAs?

They start acquiring PUFAs from 26 week of gestation — and then after birth.

Thus, the required amounts of AA and DHA must come from the mother during pregnancy, or as breast milk after birth.

What determines the amount of PUFAs in milk?

Maternal intake of PUFAs determine the amount of PUFAs in milk.

Human milk from lactating women consuming vegan or vegetarian diets has <0.1% DHA whereas the level are high in non-veg mother.

It is suggested that intakes of ~300 mg of DHA per day are necessary to achieve human milk levels of 0.3%–0.35% of DHA

What should we be cautious about when we are providing expressed breast milk to the children?

Lipid separates in standing human milk because human milk is not homogenized. Separated lipid may adhere to collection containers, feeding tubes, and syringes, thereby decreasing the delivery of lipid to the infant.

Lipid delivery is more efficient with bolus compared with continuous tubing feeding. Improved delivery of both can be achieved by using short tubing and a vertical syringe

What helps in digestion & utilization of lipid in human milk?

Milk also contains enzymes including Bile Salt Stimulated Lipase (BSSL), which allows for better lipid digestibility and better utilization.

What about the carbohydrate content of human milk?

Mainly composed of oligosaccharide and lactose

Lactose, a disaccharide consisting of glucose covalently bound to galactose, being the most abundant by far. Indeed, lactose is present in the highest concentration in humans compared to any other species, corresponding to the high energy demands of the human brain.

What is human oligosaccharide?

Human milk is composed of > 200 types of oligosaccharides mainly formed from 5 monosaccharides - L-fucose, D-glucose, D-galactose, N-acetylglucosamine and N-acetylneuraminic acid.

What is the role of Human oligosaccharide?

HMO function as prebiotics, encouraging the growth of certain strains of beneficial bacteria, such as Bifidobacterium infantis, within the infant gastrointestinal tract, protecting the infant from colonisation by pathogenic bacteria.

HMO play an important role in preventing neonatal diarrheal and respiratory tract infections.

How can HMO provide protection against virus and bacteria?

One mechanism by which HMO protect infants against gastrointestinal infection is by acting as receptor decoys.

A crucial step in the initiation of infection is the binding of pathogens to carbohydrates present on intestinal epithelial cells. HMO inhibit this process due to their analogous shapes to cell surface carbohydrates: pathogens recognize and bind to HMOs anchoring the bacteria in the mucosal layer and prevent cell adhesion to epithelial cells. Once bound, pathogens pass harmlessly from the gastrointestinal tract.

Some studies have shown reduced rate of campylobacter dysentry in breast fed infant and some have shown high incidence of calicivirus infection in children with HMO deficits.

Are HMO different in different breast milk?

The production of HMO is genetically determined, different profiles of milk oligosaccharide occur as a result of specific transferase enzymes expressed in the lactocytes. Two such genes, important for determining the HMO profile a mother produces, are the Secretor and Lewis blood group genes.

What is the protein composition of milk?

Composed of whey and casein protein.

Human milk contain higher concentration of whey and lower casein

Whey has faster gastric emptying and is soluble and easily digestible.

Casein on the other hand is found in higher concentration in bovine milk, are insoluble and forms curds in stomach, have prolonged gastric emptying and are not easily digested.

What is the whey/casein ratio in human milk?

The whey/casein ratio in human milk fluctuates between 70/30 and 80/20 in early lactation and decreases to 50/50 in late lactation. This proportion is significantly greater compared to the milk of other mammals. In cow’s milk, whey proteins represent only 18% of milk protein.

What are the main whey proteins?

The major human whey protein is alpha-lactalbumin, a nutritional protein. The major bovine whey protein is beta-lactoglobulin, which may contribute to protein allergy and colic.

Other important proteins are lysozyme, lactoferrin, IgA, alpha1-antitrypsin and antichymotrypsin, and haptocorrin.

What is the function of alpha-lactalbumin?

Iron absorption

Contains tryptophan which is the source of serotonin and provides neurotransmitter for human brain.

Which is the most abundant AAs in human breast milk?

Glutamine, the most abundant free amino acid, is nearly 20 times higher in mature milk than its lowest value in colostrum. Glutamine is important for providing ketoglutaric acid for the citric acid cycle, possibly acting as a neurotransmitter in the brain, and serving as a major energy substrate for intestinal cell.

What are the non-protein nitrogen in milk?

Non-protein nitrogen, consisting of molecules such as urea, creatinine, nucleotides, free amino acids and peptides, contribute towards ~25% of the total nitrogen present in milk. They form important components of enzyme and mediators.

Vitamins in human milk?

Human milk contains almost all vitamins but are poor in Vitamin K and vitamin D.

Minerals in human milk

Calcium,phosphorus,iron,zn,cu

What is the bioavailability of human milk?

50% whereas that of formula milk is 3-4%

What are the antibodies present in human milk?

IgA followed by IgG

IgA is present in feces of 30% of breast feed newborn on day 2 of postnatal life whereas in case of formula fed infants after 1 month as formula lack IgA.

How are IgA in breast milk produced?

The antibodies found in breast milk occur as a result of antigenic stimulation of maternal mucosa-associated lymphoid tissue (MALT) and bronchial tree (bronchomammary pathway). Therefore, these antibodies target the infectious agents encountered by the mother during the perinatal period, meaning that they also target the infectious agents most likely to be encountered by the infant.

Breast milk contains SIgA antibodies specific for many different enteric and respiratory pathogens. For example, breast milk contains antibodies protective against Vibrio cholerae, Campylobacter, Shigella, Giardia lamblia and respiratory tract infections.

Often the SIgA is thought to be protective against GBS infection

Based on the content how can we classify human breast milk?

Colostrum

Transitional milk and

mature milk

What is colostrum?

Milk produced in 1st week of life

Main function is protective and contains more Igs, growth factors,HMO and low lactose,fat

It also has purgative action that clears baby gut of meconium & helps in preventing jaundice by clearing bilirubin from the gut

Due to the presence of growth factors it helps in intestinal development

Transitional milk

In the 1st 2 weeks the milk quantity increases gradually with gradual increase in fat & protein & fall in vitamins & minerals.

At what time of the day is the human milk fat content high?

A diurnal variation in milk fat concentration occurs, with a peak fat content occurring at midmorning, and a low overnight.

Age of mother and milk composition?

Protein concentration is highest in breast milk of mothers aged 20–30; however, maternal age does not seem to influence either lipid or lactose concentrations and maternal age does not have a large impact on breast milk composition.

How does human breast milk alter the intestinal microbiota?

Breastfed infants are also known to possess a more stable and less diverse intestinal microbiota than formula-fed infants, but possess more than twice the number of bacterial cells.

How milk helps in immunological development ?

Development of gut microbiome

Contains anti-inflammatory and antibody inducing compounds like PAF-acetylhydrolase, antioxidants, interleukins 1, 6, 8 and 10, transforming growth factor (TGF), secretory leukocyte protease inhibitors (SLPI) and defensin.

They also contain pattern recognition receptors like TLR which help in microbial recognition. Also regulation of TLRs is provided by HM so that selective commensals can grow like bifidobacterium

What is bifidus factor(bifidogenic)?

A factor present in human milk that helps in growth of Bifidobactreium.

WHO recommendation on breast feeding

The World Health Organization recommends that infants should be exclusively breastfed for the first six month of life. The American Academy of Pediatrics also recommends breastfeeding for at least 12 months.