They are defined nutrients the food substances that the body needs to develop and maintain a state of good health over time. Alongside the most well-known macro-nutrients (carbohydrates, proteins and fats or lipids), there are micro-nutrients, so called because the body it needs only in small quantities. They play an essential role in regulating the body's functions as they are involved in the production of enzymes, hormones and other substances that help regulate metabolism, growth, activity, development and functioning of organs and systems This group of nutrients includes vitamins, minerals and trace elements (iron, zinc, selenium, manganese), capable of affecting the state of health of the person.Classification
The organism needs seven main elements: calcium, magnesium, sodium, potassium, phosphorus (phosphates), sulfur and chlorine (chlorides). Since they must be introduced in greater quantities than the others, they are defined macroelements.
Seven others are needed in smaller quantities and are defined trace elements or microelements: iron, copper, cobalt, manganese, molybdenum, iodine, selenium and zinc.
Finally, in fabrics there are elements such as fluorine, boron, aluminum, cadmium and chromium, the functions of which are still little known.
Since with the performance of the normal functions of the organism (physiological processes) part of these elements is lost daily, it is important to introduce the right quantities with the diet, so that the balance between income and expenditure is always in balance.
A sufficiently varied and well balanced diet ensures an adequate supply of minerals to individual needs.Macroelements
Calcium is the most abundant mineral in the body and 99% is found in the bones.
In addition to maintaining the bone structure, however, it performs irreplaceable functions in blood coagulation, muscle contraction, nerve cell functioning and cell membrane permeability.
The amount of calcium that must be introduced daily with the diet (requirement) varies according to age:
- adults, 800 milligrams per day
- children and young people, 800-1200 milligrams, with the highest values for teenagers
- pregnancy and breastfeeding, 1000-1200 milligrams
The foods richest in calcium are milk, yogurt and cheeses which, when aged, contain ten times more calcium than similar amounts of milk or yogurt. Even some vegetables, such as cabbage and broccoli, sesame seeds and small fish eaten with the bone can contribute to the introduction of calcium.
The intestinal absorption of calcium is influenced by physiological and nutritional factors. When the need for calcium is higher, ie during growth, puberty, pregnancy and breastfeeding, absorption increases.
Some substances contained in foods of plant origin, however, such as phytates (present mainly in whole grains and legumes) e oxalates (present in abundance in spinach, cabbage, and whole grains), which combine with calcium, but also with other minerals, make it insoluble and hinder its absorption.
On the contrary, lactose, amino acids, sucrose and phosphatidic acid, which keep calcium in a soluble form, seem to favor its absorption.
Lack of calcium manifests itself in various disorders (symptoms), including muscle weakness and, in the most severe forms, tetanus-like contractions and convulsions. Acute deficiencies are quite rare and seem to affect almost exclusively infants fed formula milk, which contains calcium and phosphorus in inadequate quantities. In its chronic forms, the lack of calcium causes a decrease in bone density in children; on the other hand, it is not fully defined whether it also determines a delay in growth. In adults, calcium deficiency manifests itself with osteoporosis, a condition of demineralization of the bones, to which is added a loss of organic material, which makes them fragile.
Each cell contains phosphorus, although 80% of that present in the body is found in the bone and teeth in the form of calcium phosphate; 10% is contained in muscle tissue; 1% is present in the brain and the remainder in the blood and other tissues.
Phosphorus is found in almost all foods, but its main sources are protein-rich foods.
They provide it in greater quantities:
- cereal seeds
In meat the content of phosphorus exceeds that of calcium by 15-20 times; in eggs, cereal seeds and legumes it is double; while milk and its derivatives contain more calcium than phosphorus.
Phosphorus is very abundant in technologically processed foods, usually in the form of polyphosphates (sodium hexametaphosphate), used as additives and is also found in some soft drinks in the form of phosphoric acid.
The exact phosphorus needs of the body are not known. The levels of energy and nutrient intake recommended for the Italian population (LARN) indicate for it the same quantities by weight as for calcium, i.e. 800 milligrams per day for adults (30-60 years) of both sexes.
Almost all of the magnesium contained in the organism is localized in the bone tissue, a small part is found in cells or plasma. It is involved in reactions with energy production and participates in the regulation of nerve transmission, in the excitability of muscle membranes. and neuronal.
A reduced intake or increased excretion can lead to a deficiency condition that manifests itself with disorders of varying severity:
- He retched
- alteration of the excitability of the membranes
- arrhythmia (altered heart rate)
- coma (state of absence of consciousness)
It seems that the lack of adequate amounts of magnesium also occurs during prolonged sports, due to its use during muscle activity; in this case the signals can be:
- tiredness and muscle weakness
Also the excess of the mineral, said hypermagnesemia, causes damage as it causes inhibition of the central nervous system; the resulting disorders from hypermagnesaemia consist of:
- slowing of cardiac and respiratory activity
Magnesium is present in almost all foods, even if in different concentrations. Larger quantities are contained in:
- green vegetables
- Whole grains
- dried fruit
Bananas contain good amounts of magnesium while other commonly used fruits are less important sources, like meat, fish and milk.
It has been observed that, in the absence of special needs, the introduction of 3 to 4.5 milligrams per kilo of body weight (210 - 320 milligrams per day) of magnesium is sufficient to balance the losses that occur through faeces, urine and sweat.
Sodium, contained in the blood and in the liquids present inside the cells (intracellular), is the fundamental regulator of the permeability of cell membranes and body fluids.
It is mainly contained in table salt but cheeses and most of the preserved foods (salami, sausages, etc.) are also rich in it. The recommended daily doses do not exceed 4-6 grams.
Lack of sodium causes:
- He retched
Cases of severe deficiency can even lead to:
Excessive quantities introduced in the diet can predispose to the onset of high blood pressure (hypertension) as well as causing fever, nausea, vomiting, convulsions and depression of the respiratory centers.
Potassium is present in the form of a particle with a positive electric charge (positive ion) mainly inside the cells, but also in the extracellular fluids, where it influences the activity of the skeletal muscles and the muscular tissue of the heart (myocardium). In particular, it regulates neuromuscular excitability, acid-base balance, water retention and osmotic pressure.
It is contained in almost all foods, but is especially abundant in:
- dried peas
- bananas (read the buffalo)
The average daily requirement is about 3 grams. Lack of potassium is manifested by:
- muscle weakness
- confusing states
The excess, on the other hand, determines:
- tiredness (asthenia)
- muscle cramps
- brachycardia (reduced heart rate)
- cardiac arrest, in the most serious cases
Chlorine is found mainly in combination with sodium. Dissolved in water, on the other hand, it forms hydrochloric acid, the acid found in gastric juice and which is involved in the digestion of proteins. Like sodium, chlorine regulates water balance, osmotic pressure and acid-base balance.
Saltwater fish are particularly rich in chlorine, in addition to table salt.
The daily requirement is between 0.9 and 5.3 grams which are taken with the normal use of table salt.
Lack of chlorine causes:
- muscle cramps
- mental apathy
Excess chlorine causes vomiting.
Sulfur is present in almost all the tissues of the organism but it is essential, mainly, for the formation of cartilage, hair, hair and nails.
It is mainly found in two amino acids, which are named for this sulphured (methionine and cysteine), and in three vitamins: thiamine, biotin and pantothenic acid.
Sulfur amino acids are mainly present in egg white (albumen), fish and poultry; among vegetable sources, broccoli, legumes, sesame and pumpkin seeds.
If the diet contains adequate amounts of animal protein, it is rare to find a lack of sulfur; for this reason a specific value for its needs has not been established. On the other hand, excessive intake of sulfur amino acids has been proven to cause physical development problems and poor growth.
The body uses iodine to produce thyroid hormones, molecules that regulate certain metabolic functions, including central nervous system development and body growth. Its main function, therefore, is to ensure the functionality of the thyroid gland.
The lack of iodine, one of the most serious public health problems according to estimates by the World Health Organization, causes various diseases, more or less serious depending on age and sex, such as "hyper or" hypo-production of hormone thyroid by the gland (hyperthyroidism or hypothyroidism).
The correct functioning of the thyroid is guaranteed by an adequate level of iodine introduced with the diet. Iodine is present in the human body in quantities of 15-20 milligrams and the necessary daily requirement is estimated at 150 micrograms per day. However, the presence of iodine in food and water is very variable and, often, too low compared to human needs. Contained mainly in fish, the percentage of iodine varies, however, in vegetables depending on the cultivation land.
To prevent the appearance of goiter endemic and other conditions of deficiency, the intake of iodized salt is recommended, that is salt fortified with 30 milligrams of iodine per kilo.
Selenium is a mineral that the body needs in small quantities, in the order of picograms (millionth of a millionth of a gram). It participates in the functioning of some enzymes with high antioxidant activity and, therefore, of cardiovascular protection; moreover, it regulates functioning of enzymes involved in the synthesis (production) of thyroid hormones.
In the diet, the largest amounts of selenium are found in offal and fish. Nuts, especially Brazilian nuts, and grains also contain good amounts. In plants, its quantity depends on the amount of mineral present in the soil.
The lack of selenium, which can mostly be observed in those suffering from malabsorption or following vegetarian diets in areas where the soils are poor in the mineral, manifests itself in diseases attributable to the increase in free radicals:
- premature aging
- chronic inflammatory diseases
- degenerative diseases
- increased risk of carcinomas
Excess of the mineral causes the seleniosis, toxic state that manifests itself with:
- mental confusion
- He retched
- abdominal pain with vomiting
- fragility of nails and hair
Minerals do not provide calories. Their main function is that of regulation and support for the various activities that the body carries out on a daily basis.LARN - Reference levels of intake for the Italian population: MINERALS
LARN - Reference levels of intake for the Italian population: MINERALS
Recommended intake for the population (PRI in bold) and adequate intake (AI in italics): values on a daily basis.
For the age groups, reference is made to the chronological age; for example, for 4-6 years s "means the period between the completion of the fourth and seventh year of life. The 6-12 month interval corresponds to the second semester of life.
For calcium, in postmenopausal women who are not on estrogen therapy, the recommended intake dose is 1200 milligrams.
For iron, in the 11-14 years age group, the two PRI values indicated refer respectively to adolescents who do not have, or have, menstruation; in women aged 39-59, the two PRI values indicated refer to fertile or menopausal women, respectively.Bibliography
Italian Society of Human Nutrition (SINU). LARN 2014 - Reference levels of intake for the Italian population: VITAMINS.
Italian Society of Human Nutrition (SINU). LARN 2014 - VITAMINS - Average requirement (AR): values on a daily basis
G Rindi, R Manni. Human Physiology. UTET: Milan, 2005; IX EditionIn-depth link
Ministry of Health. Daily intake of vitamins and minerals allowed in food supplements
European Food Safety Authority (EFSA). Tolerable upper intake levels for vitamins and minerals
EpiCentro (ISS). Mineral salts