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The Importance of Breast Feeding to a Baby’s Health By Richard Kieninger Doctors have long known that
infants who are breastfed contract fewer infections than those who are given
formula. Formula, which must often be mixed with water and placed in
bottles, can easily become contaminated, and indeed, infants who receive
sterilized formula suffer higher rates of meningitis and infections of the
gut, ear, respiratory tract and urinary tract than their breastfed
counterparts. Mother’s milk actively
assists the child’s immune system for the first five years or so. During
pregnancy, the mother passes antibodies (IgA, IgD, IgE, IgG, and IgM) to her
fetus through the placenta. The antibodies circulate in the infant’s blood
for weeks to months after birth, neutralizing microbes or marking them for
destruction by phagocytes (immune cells that consume and break down bacteria,
viruses and cellular debris). Other molecules
(oligosaccharides) and cells help to prevent microorganisms from penetrating
the body’s tissues. Some of them bind to microbes in the hollow space (lumen)
of the gastrointestinal tract thus blocking microbes from attaching to and
crossing through the epithelium (the layer of cells that lines the digestive
tract and other body cavities). Other molecules (lactoferrin) reduce the
concentration of particular vitamins and minerals needed by harmful bacteria
in the digestive tract. Other immune cells in human milk are phagocytes that
attack microbes directly. Another set (gamma-interferon) produces chemicals
that invigorate the infant’s own immune response. The Antibodies The most important antibody
in human milk is called IgA. It is also found in great amounts throughout the
gut and respiratory system of adults. This antibody shields other necessary
molecules from being degraded by the gastric acid and digestive enzymes in
the stomach and intestines. Infants who are bottle-fed are at risk against
ingested pathogens until they begin making IgA on their own, which usually
requires several weeks or months after birth. The collection of
antibodies contained in human milk is specially designed by the mother’s body
to attack pathogens in that child’s immediate surroundings. The mother
synthesizes these antibodies when she ingests, inhales or otherwise comes in
contact with a disease-causing agent. Each antibody she makes is specific to
that agent—binds to a single protein, or antigen, on the agent and will not
attack other substances. Because the mother makes antibodies only to
pathogens in her environment, the baby receives the protection it needs most
against the infectious agents most encountered. Furthermore, the antibodies
delivered to the infant ignore useful bacteria normally found in the gut.
These bacteria serve to crowd out the growth of harmful organisms, thus
providing another measure of resistance. The IgA molecules have a
unique characteristic in that they ward off disease without causing
inflammation-a negative side-effect of laboratory-made chemicals. In an
infant’s developing gut, the epithelial membrane is extremely delicate, and
an excess of these chemicals can do considerable damage. IgA also protects
other similar membranes in the body. Health-Enabling Molecules
Other molecules in human
milk prevent microbes from attaching to the epithelial membranes.
Oligosaccharides, which are simple chains of sugars, have a structure that
resembles the binding sites through which bacteria gain entry into the cells
lining the intestinal tract. This structure allows these sugar-like molecules
to intercept bacteria, forming harmless complexes that the baby excretes. In
addition, human milk contains large molecules called mucins that include a
great deal of protein and carbohydrate. They also adhere to bacteria and
viruses and then are harmlessly eliminated from the body. The protein molecule
lactoferrin binds to two atoms of iron, making them unavailable to the
pathogenic bacteria that thrive on iron. It is especially effective against
Staphylococcus aureus. Lactoferrin also disrupts the process by which
bacteria digest carbohydrates, further limiting their growth Similarly, the
binding of protein B12 deprives
microorganisms of vitamin B12. Bifidus factor, one of the
oldest known disease-resistance factors in human milk, promotes the growth of
a beneficial organism named Lactobacillus bifidus. Free fatty acids present
in human milk can damage the membranes of enveloped viruses, such as the
chicken pox virus, which are packets of genetic material encased in protein
shells. Interferon, present in
colostrum—the scant, sometimes yellowish milk a mother produces during the
first few days after birth—also has strong antiviral activity. Fibronectin,
present in large quantities in colostrum, can make certain phagocytes more
aggressive so that they will ingest microbes even when the microbes have not
been tagged by an antibody. Like IgA, fibronectin minimizes inflammation and
aids in repairing tissue that is otherwise damaged by inflammation. Activities of Immune Cells
Immune cells are abundant
in human milk. They consist of white blood cells and leukocytes that fight
infection and activate defense mechanisms. The highest concentration is found
in colostrum. Another type is called neutrophils. This immune cell type is
less aggressive than blood neutrophils and virtually disappears from breast
milk six weeks after birth and has the function of protecting the breast from
infection. The next most common milk
leukocyte is the macrophage. Macrophages make up some 40 percent of all the
leukocytes in colostrum. Aside from being phagocytic, the macrophages in breast
milk manufacture lysozyme (an enzyme that destroys bacteria by disrupting
their cell walls) increasing its amount in the infant’s gastrointestinal
tract In addition, macrophages in the digestive tract can activate
lymphocytes into action against invaders. Lymphocytes constitute the
remaining 10 percent of white cells in the milk. About 20 percent of these
cells are B lymphocytes, which give rise to antibodies; the rest are T
lymphocytes, which kill infected cells directly or send out chemical messages
that mobilize other components of the immune system. Milk lymphocytes behave
differently from blood lymphocytes. Those in milk, for example, proliferate
in the presence of Escherichta coli, a bacterium that can cause
life-threatening illness in babies, but they are far less responsive than
blood lymphocytes to invaders posing less threat to infants. Milk lymphocytes
also manufacture several chemicals-including gamma-interferon, a migration
inhibition factor and monocyte chemotactic factor-that strengthens an
infant’s own immune response. Maturation of the Infant’s Immune System
Several studies indicate
that some factors in human milk induce an infant’s immune system to mature
more quickly than it would were the child fed artificially. Certain hormones in milk
(cortical) and smaller proteins (including epidermal growth factor, nerve
growth factor, insulin-like growth factor and somatomedin C) act to close up
the leaky mucosal lining of the newborn, making it relatively impermeable to
unwanted pathogens and other potentially harmful agents. Other compounds in human
milk stimulate a baby’s own production of IgA, lactoferrin and lysozyme.
These three molecules are found in larger amounts in the urine of breastfed
babies than in that of bottlefed babies. These molecules are triggered into
production in the mucosa of the infant’s urinary tract by breastfeeding. Recent clinical studies
have demonstrated that the breast-fed infant has a lower risk of acquiring
urinary tract infections. The studies have also shown that an unknown factor
in human milk causes breast-fed infants to produce more fibronectin on their
own than do bottle-fed babies. By protecting infants
against infection until their bodies can protect themselves, breast milk
supplies far more than just nutrition. |
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