By Dr. Alessio Dini
By nutritive element we mean that fundamental substance for our metabolism, therefore for the production of energy necessary for life.
The nutritional principles are contained in foods in various ways and according to the needs they are classified in macronutrients and micronutrients.
Protein
Nitrogen molecules formed from carbon, hydrogen, oxygen and nitrogen, are among the most complex organic compounds and are essential constituents of all cells. From the chemical point of view, proteins are macromolecules formed by the union of simpler units, amino acids. The amino acids are joined together by a covalent bond called the peptide bond.
Proteins perform multiple functions and represent about 12-15% of body mass.
The naturally occurring amino acids are numerous, but only 20 of them can be used by our body for protein synthesis. Eight of these are defined as "essential", meaning that they are not synthesized in sufficient quantities and must therefore be taken with the diet.
Foods of animal origin have a better amino acid profile because they generally contain all the essential amino acids in good quantities. Unlike these, foods of plant origin usually have deficiencies of one or more essential amino acids. However, these deficiencies can be overcome through the right food associations, such as pasta and beans. In this case we speak of mutual integration because the amino acids of which the pasta is lacking are supplied by the beans and vice versa.
Normally 92% of the proteins introduced with the diet are absorbed (97% of the animal ones and 78% of the vegetable ones).
Nutritionists recommend that during the day a quantity of proteins equal to about 15-20% of the total daily calorie intake, equal to 0.8-1 g of protein per kg of body weight, is taken. These proteins should derive 2/3 from products of animal origin and 1/3 from products of vegetable origin.
Proteins abound in meat, poultry, fish, milk, cheese, yogurt, but also in vegetables, legumes, cereals, nuts, seeds and vegetables.
An excessively high protein diet can cause:
- storage fat accumulation (if the inserted proteins go beyond the total caloric requirement);
- excessive formation of toxic nitrogenous waste (ammonia, creatinine, uric acid, urea, etc.).
Excess nitrogenous waste creates difficulties in the replacement and reconstitution of new cellular structures, kidney and liver fatigue, blood acidosis, difficulty and digestive disorders.
Carbohydrates
Carbohydrates, also called carbohydrates, are substances formed by carbon, hydrogen and oxygen. They have molecular formula (CH 2 O) n and are mainly contained in foods of vegetable origin.
Based on their chemical structure, carbohydrates are classified into simple (monosaccharides and disaccharides) and complexes (oligosaccharides and polysaccharides).
Monosaccharides are classified. based on their number of carbon atoms in trioses, tetrosi, pentose, hexoses and so on; hexoses (glucose, fructose, galactose) are the most important from a nutritional point of view.
Glucose is used as a source of energy by both animals and plants; it is the main product of photosynthesis and is the fuel of cellular respiration. When present in excess, glucose is converted into glycogen, a glucose polymer and the animals' main energy reserve.
Simple and / or complex sugars, although in a very variable percentage, are almost present in all foods.
Particularly rich in complex carbohydrates are above all cereals (wheat, corn, rice, barley, spelled, oats etc.), potatoes, chestnuts, some legumes (in particular, peas and beans), pumpkin and roots (like carrots, sugar beets, etc.).
Simple sugars are more present in fruit, especially in the ripe one and in some types more than in others (bananas, figs, persimmons, pears, tropical fruits, peaches, apricots). In addition to, of course, honey, honeydew and natural syrups.
Carbohydrates should constitute the predominant share of daily caloric intake, ideally around 55-65%; of these and 80% should be complex.
Excessive consumption, in addition to favoring weight gains and dental pathologies, predisposes to the development of insulin resistance, type 2 diabetes, and different hormonal alterations.
Lipids
Heterogeneous group of molecules, united by the characteristic of being insoluble in water.
They perform important functions in the body, including that of energy intake (1 g of lipids provides 9 Kcal, against the 4 Kcal of carbohydrates and proteins); they are constituents of cell membranes (phospholipids and cholesterol); they are precursors of compounds that carry out important regulatory functions in the body (steroid hormones, vitamin D); they are our subcutaneous thermal insulator and support our organs.
The most important lipids from the point of view of human nutrition are: fatty acids, triglycerides, phospholipids and cholesterol.
Recall that lipids are also essential for a balanced diet and that among the unsaturated fatty acids we find essential fatty acids such as alpha-linolenic and linoleic acid, important precursors of prostaglandins, thromboxanes and leukotrienes, substances that mediate the response inflammatory and involved in the immune and cardiovascular system.
Essential fatty acids are contained in fish, nuts, sunflower oil, corn and some plant extracts.
Vitamins
Vitamins are a very heterogeneous set of chemical substances, normally required in minimal quantities for the body's needs, in which they regulate a series of metabolic reactions, often functioning as coenzymes. Vitamin deficiency is usually defined as hypovitaminosis when the vitamin is present in insufficient amounts in the body, and avitaminosis in the much rarer cases in which it is totally absent.
Vitamins can be divided into two large groups:
- water-soluble: can not be accumulated by the body, therefore to be taken daily with food. These are all the B vitamins, including folic acid, vitamin H, PP and C.
- liposoluble: they are absorbed along with dietary fat and accumulated in the liver. The deficiency manifests itself therefore following a failed recruitment for long periods. Vitamin A, D, E and K are part of it.
Minerals and water
Mineral salts are inorganic substances which, while representing only 6% of body weight, perform essential functions for human life: they participate in cellular processes, such as the formation of teeth and bones, are involved in the regulation of balance hydrosaline, in the activation of numerous metabolic cycles and are decisive factors for the growth and development of tissues and organs.
Mineral salts do not directly supply energy, but their presence makes it possible to realize precisely those reactions that release the energy we need.
They cannot be synthesized independently, they are assimilated through water and food, or as a condiment added to food, such as table salt.
Mineral salts can be divided into:
- Macroelements: they are present in the body in discrete quantities. The daily requirement is of the order of grams or tenths of a gram.
- Trace elements or microelements: they are present only in traces in the body and the daily requirement ranges from a few micrograms to several milligrams.
Water : a fundamental component of our diet. Not for nothing the human body is formed for as much as 60% of water. Furthermore, the body has no reserves from which it can draw. The daily intake should be at least 1.5 - 2 liters.
