Human milk and breast feeding: an update on the state of the art.

Abstract

Current approaches to infant feeding have been based on the level of available knowledge of nutritional requirements of full term and low birth weight (LBW) infants and on established cultural traditions in many contemporary societies. This discussion summarizes existing information about infant nutrition and immunobiologic aspects of human milk, which may influence the choice of breast versus bottle feeding of infants in different parts of the world. The average caloric requirement for a normal full term infant from the 2nd day of age through the 1st year of life is estimated to be about 100-110 Kcal/kg/day. Caloric intake of less than 80 Kcal/kg/day is usually insufficient for physiologic needs and intakes over the average requirement may be associated with obesity. The minimum requirement for protien has been estimated to be about 1.8 gm/100 Kcal and protein intake of over 4.5 gm/100 Kcal may result in an increased urea nitrogen retention. The nutritional requirements of premature and LBW infants have not been clearly established, but the nutritional needs of a LBW infant appear to be significantly higher than the requirements of a normal full term infant. The chemical composition of human milk exhibits considerable variation between different individuals and in the same individual at different times of lactation, as well as between samples obtained from mothers of LBW infants and full term infants. Fresh milk contains a wealth of components that provide specific and nonspecific defenses against infectious agents or other macromolecules. The concentrations of protein, whey protein nitrogen, sodium and potassium in cow's milk are 2-3 times higher than in human milk. Only limited information is available about the spectrum of environmental chemical and toxins present in cow's milk. The composition of human milk meets the minimum requirements for protein and calories for a growing full term infant, despite the fact that protein content of pooled human milk is low (0.9 gm/ml). Breastfeeding seems to result in a more balanced solute load because breastfed babies appear to require less water than babies fed on cow's milk. Commercial formula products often require reconstitution and supplementation with certain additives during manufacture or at the time of its feeding to the infant. Careful, but sparse epidemiologic studies conducted recently in several rural and urban settings, demonstrated a striking resistance of breastfed infants to colonization by coliform organisms. In modern times possibly the single most important consideration for the use of breastfeeding is its cost. Infants fed human milk do not grow as rapidly as those fed most commercial formulas, but there is no evidence to suggest that rapid growth is a desirable goal of nutrition for normal neonates. Conclusive evidence of overwhelming nutritional advantages of human nilk and breastfeeding over commercial milk products (which are properly reconstituted under sterile conditions) is not available at this time.