ABSTRACT: Protective components in human milk include immunoglobulins, other antiinfective proteins, and properties which stimulate the protective development of the infant's gastrointestinal tract. Human milk is high in vitamin C and lactose, and low in iron, calcium and phosphorus. Vitamin D may be present in clinically significant amounts in a water soluble form. Although breast milk is low in protein (1–1½g/100 ml), this is sufficient to maintain normal growth in full-term infants. Mothers of preterm infants have been found by some, but not all, investigators to have more protein in their breast milk than is found in the milk of full-term mothers. Breast milk protein differs from that in cow's milk in both quantity and quality. Human milk includes zinc and folate binding agents, thyroid hormone, increased amounts of well-absorbed lipids and highly bio-utilizable proteins.