The carbohydrate family includes a variety of chemicals. It has always been an important part of human diet. Carbohydrates not only act as a 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 polysaccharides. Dietary fiber, another critical dietary component, also consists of certain oligo- and polysaccharides, which are not digested in the human small intestine by the endogenous enzymes.
Monosaccharides – The simplest sugars, such as glucose, galactose, and fructose. They provide a 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, most of them 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 saccharide units. Examples are raffinose (Galactose-Glucose-Fructose) and stachyose (Galactose-Galactose-Glucose-Fructose). More complex oligosaccharides include fructooligosaccharides (FOS), galactooligosaccharides (GOS), and etc. Codex Alimentarius Commission has defined 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, hemicellulose, pectin, and chitin.