The carbohydrate family includes a variety of chemicals. It has always been an important part of human diet. Carbohydrates not only act as source of energy, they also have other physiological influences, some of which are beneficial but others undesired. Structurally carbohydrates can be categorized into mono-, di-, oligo-, and poly-saccharides. Dietary fiber, another critical dietary component, also consists of certain oligo- and poly-saccharides, which are not digested in human small intestine by the endogenous enzymes.
Monosaccharides – The simplest sugars, such as glucose, galactose and fructose. They provide sweet taste in foods and are readily converted to energy via quick absorption into the bloodstream.
Disaccharides – Two molecules of monosaccharides undergo condensation to form various disaccharides. The most common ones are sucrose (Glucose-Fructose), maltose (Glucose-Glucose), and lactose (Galactose-Glucose). Similar to monosaccharides, they can be readily utilized to provide energy after specific endogenous enzymes convert them to their corresponding monosaccharides.
Oligosaccharides – Made up of three to approximately ten monomeric units. Examples are raffinose (Galactose-Glucose-Fructose) and stachyose (Galactose-Galactose-Glucose-Fructose). Codex Alimentarius Commission has included non-digestible oligosaccharides as a part of dietary fiber.
Polysaccharides – Long chains of monosaccharides (usually >>10). This category includes starch (consisting of amylose and amylopectin), xylan, mannan, cellulose, pectin and chitin.