Carbohydrates

of glucose to 4.2 Kcal of starch. Of these calories about 10% is used by the body for the processes of digestion and absorption.

Based on their chemical structure, carbohydrates are classified into simple and complex.

Simple carbohydrates, commonly called sugars, include monosaccharides, disaccharides and oligosaccharides. In nature there are more than 200 monosaccharides which differ in the number of carbon atoms present in their chain.

Hexoses (fructose, glucose, galactose) are the most important from a nutritional point of view.

it is normally found in foods, both in free form and in the form of polysaccharide. It constitutes the form in which the other sugars must be transformed in order to be used by our body. Only 5% of the total amount of carbohydrates present in our body is represented by glucose circulating in the blood. Glycemic index = 100 FRUCTOSE found in abundance in fruit and honey; it is absorbed in the small intestine and metabolized by the liver which transforms it into glucose. Its glycemic index is very low, equal to 23 GALACTOSE in nature it is not found free but linked to glucose it forms lactose, the sugar of milk.

Oligosaccharides are formed by the union of two or more monosaccharides (maximum 10). They are found mainly in vegetables and in particular in legumes. The best known, since they are important from a nutritional point of view are disaccharides (sucrose, lactose and maltose).

. Its glycemic index is 68 ± 5 LACTOSE glucose + galactose; it is the sugar of milk and the least sweet of the disaccharides. Its glycemic index is 46 ± 6 MALTOSE glucose + glucose; little present in our diet is found mainly in beer, cereals and sprouts. Its glycemic index is 109

Among the oligosaccharides we mention maltodextrins.

Maltodextrins are oligosaccharides deriving from the hydrolysis process of starches. They are used as energy supplements and can be useful in endurance sports. They provide short and medium term energy without straining the digestive system too much.

Polysaccharides are formed by the union of numerous monosaccharides (from 10 to thousands) through glycosidic bonds. Vegetable polysaccharides (starches and fibers) and polysaccharides of animal origin (glycogen) are distinguished. Polysaccharides containing a single type of sugars are called homopolysaccharides, while those containing different types of monosaccharides are called heteropolysaccharides.

, beans and sweet potatoes. In nature it is present in two forms, amylose and amylopectin. The higher the amylopectin content, the more digestible the food is. FIBERS they are structural polysaccharides, the most important of which is cellulose. Our organism is not able to use them for energy purposes, but their fermentation in the intestine is essential to regulate the absorption of nutrients and to protect our body from numerous pathologies. They are divided into water-soluble and non-water-soluble ones. The former chelate by interfering. with the absorption of nutrients, including cholesterol, the latter attract water, accelerating gastric emptying. The caloric contribution of fiber in the diet is zero. GLYCOGEN it is a polysaccharide similar to amylopectin used as a source of primary energy storage and reserve. It is stored in the liver and muscles up to a maximum of 400-500 grams. The glycogen present in animals is almost completely degraded at the time of slaughter so it is present in extremely small quantities in food.

Proportions of amylose and amylopectin in the starch molecule of different origins

Foods

Amylose (%)

Amylopectin (%)

wheat

25,0

75,0

corn

24,0

76,0

rice

18,5

81,5

potatoes

20,0

80,0

tapioca

16,7

83,3

it begins in the mouth where the enzymes in the saliva begin the breakdown of complex carbohydrates. In the stomach, the action of salivary enzymes is interrupted by the acidic environment and resumes in the small intestine where, thanks to pancreatic juices (α-amylase enzyme), the polysaccharides are reduced to monosaccharides.

While glucose is absorbed rapidly (both by osmotic gradient and by active transport), fructose is absorbed more slowly, through a facilitated diffusion mechanism, which is the basis of its low glycemic index.

MORE: Functions of carbohydrates and their role in Diet and Sport "