Janice M. Vickerstaffjoneja, PhD
Can Fam Physician 1992;38:1849-1855.
The protective agents in colostrum and mature breast milk include specific antibodies, enzymes, leukocytes and their products, antibinding factors, antiviral factors, promoters of a protective intestinal microflora, and immune stimulators. These agents persist through the length of the infant’s digestive tract, are unaffected by gastric acid and digestive enzymes, are present throughout lactation, and protect by noninflammatory mechanisms.
The incidence and severity of infections in breast-fed infants are significantly lower than bottle-fed infants. Although this was originally thought to be the result of increased exposure to contamination from bottle-feeding, recent research shows that specific agents in breast milk protect the exclusively breast-fed baby from infection even when pathogenic microorganisms have been ingested. During the past decade several of these agents have been identified; also, the way in which the defense system contained in breast milk operates in breast-fed infants is now beginning to be understood.