Eating means coping with a fundamental need of the organism: with food we introduce into the body all that is necessary for living, energy and nutritive principles.
The organism uses energy for all the activities necessary for its survival: the only source of energy that our body is in a position to use is the one supplied from nourishment.
The calorie is the unit measure that quantifies energy.
The nutritive principles, or nourishments, are substances that carry out specific functions within the human body, favouring and guaranteeing in some way the growth, the proper functioning and the health of the organism.
Nutriments are substances classified in groups based on determined chemical characteristics: proteins, carbohydrates, fats, vitamins, minerals and water.
Various nutritive principles are present in different quantities in all the food: no nourishment contains them all in the required quantities and, therefore there is no nourishment that alone can satisfy all our nutritive needs.
For this an adequate and correct diet requires the intake of various foods, so as to ensure the daily required nutritive intake to our organism.
The nutritive substances that carry calories are the carbohydrates, the proteins and the fats; vitamins, minerals and water are not a source of energy, but are equally indispensable for the human organism.
Let’s analyse quickly the functions of the different nutritive substances:
thanks to the extreme variability of their structure, are substances able to carry out a high number of biological functions: they are the main constituents of tissues, enzymes, some hormones and other substances that govern important processes of our organism.
Proteins are present in many food of animal and vegetable origin (meat, eggs, milk, vegetables).
Once ingested, they are broken down by the protease enzymes in their constituent parts, the AMINO ACIDS, which, once absorbed, are carried by the blood to the tissues in need of them.
Out of the twenty amino acids that constitute proteins, eight, the so called essential amino acids, must be taken in the right proportions, with food, since the organism is not able to synthetise them; a deficiency of even one of these, may harm the general health of the organism.
are substances of great biological importance, such as glucose, saccharose, starch, cellulose, etc..
They supply the most consistent portion of energy, representing especially a type of energy immediately available.
In food, carbohydrates are present in forms that differ from a chemical point of view: there are in fact complex carbohydrates, with an elevated nutritive power, and simple sugars. Amongst the latter, glucose is certainly the source of energy preferred by the organism.
also called lipids, constitute the energy reservefor the organism.
During the digestive phase they are broken down into fatty acids:
they are distinguished in saturate fatty acids (especially of animal origin) and insaturate fatty acids (mostly present in food of vegetal origin) depending on their different chemical structures and their different nutritional properties.
are substances of an inorganic nature that must be taken with food because they are necessary for a series of functions of the organism: the formation of tissues, enzymatic reactions, muscular contraction, transmission of nervous impulses, etc..
They are subdivided in two classes: the macroelements (chlorine, calcium, phosphorus, magnesium, potassium, sodium, sulphur) and the oligoelements (chromium, iron, iodine, fluorine, copper, etc..).
are compounds of an organic nature that take part in various physiological processes.
They are classified according to their solubility in water or fats, in liposoluble vitamins (vit. A, vit. D, vit. E, vit. K if administered in excess, are accumulated in the liver and in adipose tissues) and hydrosoluble vitamins (vit. C, vit.B1, vit.B2, vit. B6, vit. B12, niacin, folic acid, pantothenic acid, biotin; these vitamins must be administered daily).