Doctors have long known that infants who are breast-fed contract fewer infections than do those who are given formula. Until fairly recently, most physicians presumed that breast-fed children fared better simply because milk supplied directly from the breast is free of bacteria. Formula, which must often be mixed with water and placed in bottles, can become contaminated easily. Yet even infants who receive sterilized formula suffer from more meningitis and infection of the gut, ear, respiratory tract and urinary tract than do breast-fed youngsters.

The reason, it turns out, is that mother’s milk actively helps newborns avoid disease in a variety of ways. Such assistance is particularly beneficial during the first few months of life, when an infant often cannot mount an effective immune response against foreign organisms. And although it is not the norm in most industrial cultures, UNICEF and the World Health Organization both advise breast-feeding to “two years and beyond.” Indeed, a child’s immune response does not reach its full strength until age five or so.

Several studies indicate that some factors in human milk may induce an infant’s immune system to mature more quickly than it would were the child fed artificially. For example, breast-fed babies produce higher levels of antibodies in response to immunizations. Also, certain hormones in milk (such as cortisol) and smaller proteins (including epidermal growth factor, nerve growth factor, insulinlike 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. Indeed, animal studies have demonstrated that postnatal development of the intestine occurs faster in animals fed their mother’s milk. And animals that also receive colostrum, containing the highest concentrations of epidermal growth factor, mature even more rapidly.

Other unknown compounds in human milk must stimulate a baby’s own production of secretory IgA, lactoferrin and lysozyme. All three molecules are found in larger amounts in the urine of breast-fed babies than in that of bottle-fed babies. Yet breast-fed babies cannot absorb these molecules from human milk into their gut. It would appear that the molecules must be produced in the mucosa of the youngsters’ urinary tract. In other words, it seems that breast-feeding induces local immunity in the urinary tract.

In support of this notion, recent clinical studies have demonstrated that the breast-fed infant has a lower risk of acquiring urinary tract infections. Finally, some evidence also suggests that an unknown factor in human milk may cause breast-fed infants to produce more fibronectin on their own than do bottle-fed babies.

All things considered, breast milk is truly a fascinating fluid that supplies infants with far more than nutrition. It protects them against infection until they can protect themselves.

Adopted from an article by By Jack Newman, MD, FRCPC
Courtesy: http://www.breastfeedingonline.com

JACK NEWMAN founded the breast-feeding clinic at the Hospital for Sick Children in Toronto in 1984 and serves as its director. He has more recently established similar clinics at Doctors Hospital and St. Michael’s Hospital, both in Toronto. Newman received his medical degree in 1970 from the University of Toronto, where he is now an assistant professor. He completed his postgraduate training in New Zealand and Canada. As a consultant for UNICEF, he has worked with pediatricians in Africa. He has also practiced in New Zealand and in Central and South America.