Foods or foods are defined as edible products of various nature and origin that humans must take to draw energy (calories) and the nutritional principles necessary to ensure the normal performance of physiological functions.
Nutrient principles: Classification and functions in the body
The nutritional principles are the chemical constituents, organic and inorganic, which are found more or less in all foods but in different quantities from one to the other. A food can be considered complete when it contains all the harmonically distributed food principles. With the exception of breast milk for babies, there are no complete foods and this is why our body needs a varied and balanced diet.
The various nutritional principles present in foods can be divided into:
- Organic: proteins, lipids, glucides, vitamins
- Inorganics: water, mineral salts, oxygen
and in:
- Macronutrients: proteins, lipids, glucides, can be used by the body only after digestion which transforms them into simple and easily assimilable compounds.
- Micronutrients (vitamins and essential mineral salts) introduced in small quantities, are not modified by digestion or absorption and are essential for the regular completion of vital processes (for example, of enzymatic reactions)
The functions of nutritional principles are numerous:
- ENERGY FUNCTION: supplying energy material for the production of heat, work or other forms of energy (proteins, carbohydrates, lipids)
- CONSTRUCTIVE and repairing FUNCTION: supplying plastic material for tissue growth and repair (protides and minerals)
- REGULATING FUNCTION, balancing, protective: providing "regulating" material making metabolic reactions (minerals and vitamins) possible
| FUNCTION | NUTRITIONAL PRINCIPLES | FOODS OR FOODS | |
| ENERGY | carbohydrates | sugars | honey, sugar and derivatives, ripe sugary fruit (grapes, figs, bananas) |
| polysaccharides | cereals and derivatives (bread, crackers, flour, pasta, rice, etc.), potatoes, floury plant foods (chestnuts) | ||
| Lipids | butter, lard, lard, vegetable oils, animal fats, oily fruit (walnuts, almonds), cheeses and fatty meats | ||
| Protein | meat in general, fish, legumes, dried fruit, eggs | ||
PLASTIC or CONSTRUCTION | Mineral salts | Football | milk, legumes, cheeses, fish, eggs, rocket, spinach |
| Phosphorus | fish, meats, cheeses, eggs, legumes, cheeses, whole grains | ||
| Iron | meat in general, eggs, legumes, fish, dried fruit | ||
| Iodine | sea fish, seaweed, vegetables grown in iodine rich soils | ||
| Protein | meat in general, fish, legumes, dried fruit, eggs | ||
PROTECTRESS or GOVERNING | Vitamins | A (retinol) | red and yellow vegetables, offal, fish liver oil, egg yolk |
| B1 (thiamine) | whole grains, legumes, pork | ||
| B2 (riboflavin) | milk, cheese, dairy products, offal and eggs (ubiquitous distribution) | ||
| PP (nicotinamide) | cereals, especially not very refined, dried legumes, meat, eggs, fishery products and offal | ||
| C (ascorbic acid) | Fruit (citrus fruits, pineapple, kiwi, strawberries, cherries, etc.), vegetable tubers (potatoes) and some fresh vegetables (broccoli and similar) | ||
| D3 (cholecalciferol) | liver, fish oils, some marine fish (herring, salmon, sardine), butter, egg milk | ||
The foods can instead be classified in seven groups:
| Group | Food | Nutrients provided | To be preferred |
| 1 | meat, fish, eggs | high quality protein, iron some B vitamins | white meats and fish, without completely excluding eggs and red meat from the diet |
| 2 | milk and derivatives | calcium, high quality proteins, some B-group carbohydrate vitamins, | skim milk and low-fat cheeses (ricotta, milk flakes, lean mozzarella) |
| 3 | cereals, tubers and derivatives | low quality proteins, vitamins of group B | whole grains (one or two servings per day) |
| 4 | legumes | medium quality proteins, iron, some B group vitamins | at least two to three servings a week |
| 5 | Seasoning oils and fats | fat | vegetable oils (uncooked raw) |
| 6 and 7 | vegetables and fruit | vitamins (especially A and C), minerals, fiber | vary at the most, at least four portions a day |
Energy content of foods
To quantify the energy content of a food, Kilocaloria (in Italy) or KiloJoule (a calorie equals 4.188 joules) is used.
The calorific value of a food depends on its composition in nutritional principles:
macronutrients
- each gram of carbohydrates provides an average of four kilocalories
- each gram of fat provides an average of nine kilocalories
- each gram of protein provides an average of four kilocalories
MICRO
- they do not supply energy but are equally essential (regulatory function)
For this reason, animal fats and oils are by far the most calorie-rich foods (high lipid percentage); vegetables provide very few calories instead (contains a minimal percentage of carbohydrates while the protein and fat content is often negligible). The consumption of vegetables, due to their high fiber content, vitamins and mineral salts, is often encouraged without any quantitative or qualitative imposition (each person chooses the vegetables they prefer, taking care to alternate between them).
Food calories »
See also: Whole foods or refined foods
