Polyhydric alcohols are glucides with a molecule similar to monosaccharides, but with a hydroxyl function instead of the aldehyde or ketonic one.
They are found as such only in fruit ( sorbitol ) in small quantities, however they are used as sweeteners in an ever-increasing number of low-calorie or acariogenic foods (sweets, chewing gum) given their limited energy power.
The lactitol, maltitol and isomalt disaccharides are hydrolyzed only minimally by the action of intestinal glycosidases.
The absorption of polyalcohols in monomeric form (mannitol, sorbitol, xylitol) occurs by passive diffusion, but at a speed much lower than that of glucose and fructose.
From this depends, in all probability, their partial malabsorption, with the consequent laxative effect if they exceed 20 ÷ 30 g / day (20 g per day for mannitol, 50 g for sorbitol and xylitol and 100 g for maltitol).
For polyhydric alcohols, according to the DL 16 February 1993 n ° 77 (GU n ° 69, 24/3/1993) which regulates the nutritional labeling of food products, a caloric value of 2.4 kcal / g is attributed.
D-sorbitol : it is a hexose polyol present in the fruits of many Rosaceae, in particular in Sorbus aucuparia (Sorbo degli uccellatori) and in the thallus of some algae. Uses: It is widely used in the pharmaceutical industry (it has cholagogic properties, mild laxative) and agro-food (sweetener for diabetics); but it is cariogenic.
Meso-xylitol : obtained by hydrogenation of D-xylose, obtained from maize, wood, straw. Uses: used as a sweetener to replace sucrose, without exceeding it because it can give gastrointestinal disorders (meteorism and diarrhea). Not cariogenic, widely used in the confectionery industry.
D-mannitol : it is extracted from the manna of the ash tree and from the thallus of brown algae (Laminariales). Uses: It is not metabolizable, used as a cholecystokinetic and laxative and as a sweetener for diabetics.
Ciclitoli : poly-hydroxy-cyclo-alkanes. Inositol is the best known and most important; it is an alcohol, cyclic, very widespread in the animal organism (it forms certain phospholipids) and in vegetables in the form of phytic acid, esterified with 6 molecules of phosphoric acid, it forms a part of the included aleuronic vacuolar solids. Uses: hepatoprotective, phosphorus reserve.
Other plants give natural sweeteners, which are used instead of sucrose to try to prevent and / or correct disease states, such as tooth decay, diabetes mellitus, cardiovascular disease, overweight. Licorice, to cite an example, contains contains a terpene (glycyrrhizin) with a sweetening power up to 100 times higher than normal kitchen sugar. This strong sweetener favors the retention of sodium and water in animal cells, consequently reducing the body's need for water (hypertensive properties).
See also: Artificial sweeteners
