Chapter 4 - Carbohydrates in Milks: Analysis, Quantities, and Significance

Abstract

This chapter discusses about carbohydrates in types of milk. The principal carbohydrate in most types of milk is lactose. Its concentration represents a balance between the high nutrient requirements of the infant and the constraints of carbohydrate concentration in milk due to osmolarity. Most types of milk contain small amounts of glucose and galactose, the biosynthetic precursors of lactose. This chapter compiles, summarizes, and analyzes the most recent relevant information available on the carbohydrate content of milk. Levels of lactose are considered to be the most consistent of the macronutrients in human milk; 75 % of the total variance is contributed by the heterogeneity of individuals. In addition to lactose, the carbohydrates of human milk include nucleotide sugars, glycolipids, glycoproteins, and oligosaccharides. Lactose, the principal sugar of human and most other terrestrial eutherian milk, is, for the most part, unique to this fluid, although small amounts have been found in other sources, including plants. The lactose levels increase as lactation is established and tight junctions form in the mammary epithelium, limiting the movement of materials by the paracellular pathway. Lactose concentrations in mature human milk are quite stable showing little or no change in response to a variety of environmental or dietary challenges and little variation across genetically distinct groups. We speculate that the galactose of milk could play a unique role in providing the requirements of the rapidly developing infant brain.