By Dr. Davide Marciano
Carbohydrates are the primary fuel of the human machine. Their main task is the production of energy, essential for the vital processes of the organism.
From the chemical point of view they are made up of Carbon, Hydrogen and Oxygen in the ratio 1: 2: 1.
Based on their constitution and absorption, they are divided into:
MONOSACCARIDES, carbohydrates with a single sugar molecule (glucose, fructose, galactose),
DISACCARIDES, carbohydrates with two sugar molecules (maltose, lactose and sucrose)
POLISACCHARIDES, carbohydrates with 3 or more sugar molecules (starches, glycogen and fibers).
Monosaccharides and disaccharides are called sugars or simple carbohydrates.
Polysaccharides, on the other hand, are called complex carbohydrates or glucose polymers.
They are stored in the form of glycogen in the muscles (fuel reserve for the synthesis of ATP necessary for muscle activity) and in the liver (glucose reserve for maintaining the blood levels of this sugar).
The body, in resting conditions, consumes 160g of glucose a day, of which 120g are used by the brain (this is one of the reasons why you should never take less than 160g of carbohydrates a day).
Simple glucides
For the purpose of our treatment the most important monosaccharides are glucose, also called dextrose, and the fructose or fruit sugar (only ripe fruit is rich in this sugar).
These two monosaccharides, like all other carbohydrates, differ according to the speed of absorption. Each food has been assigned a Glycemic Index (IG) which corresponds to the speed with which carbohydrates arrive in the blood stream.
High glycemic index carbohydrates, such as dextrose, are quickly used for energy purposes even if what happens is totally the opposite.
In fact, carbohydrates with a high glycemic index induce an immediate influx of blood sugars, raising the blood sugar levels; the sudden increase of the latter stimulates the release of insulin which takes glucose away from the blood stream, thus lowering energy levels.
Complex glucides
The polysaccharides, as we have already said, are:
- Starch is the form under which plants store their carbohydrates, in fact we find it in cereals and vegetables, especially in potatoes.
- Glycogen is the form under which animals store glucose.
- Cellulose, finally, is a particular type of carbohydrate that constitutes the physical structure of a plant. However, man is not able to use it as an energy source because our digestive system is not able to break the bonds of this polysaccharide.
However, cellulose is very important as FIBER. It plays a fundamental role in the diet thanks to the contribution of bran. The latter promotes efficient functioning of the intestine and contributes to the passage of sugars in the blood stream. In addition, the dietary fiber serves to soften the faeces and to favor a normal elimination, also giving a greater sense of satiety.
Absorption of carbohydrates
In the small intestine all carbohydrates are split into monosaccharides: glucose, fructose, galactose, levulose.
In this way they manage to pass through the intestinal walls. These nutrients are then transported to the liver, where all monosaccharides are converted to glucose.
In fact all the carbohydrates to be assimilated are split into glucose.
The liver can use glucose by storing it inside as a glycogen, or it can return it to the bloodstream for use as an energy source.
When there is more glucose in the body than is necessary for immediate energy, the body transforms this surplus into muscle glycogen.
Only after the glycogen reserves have recovered, does the body take the remaining glucose from the blood and store it as fat.
Carbohydrates also contribute to the metabolization of proteins and to the elimination of nitrogenous waste resulting from the utilization of proteins.
They also play a fundamental role in the demolition of fats; always remember that "fats burn under the flame of carbohydrates".
