Content

Introduction

Introduction

They are defined nutrients those chemical components of foods that are needed by the body to develop and to maintain a state of good health over time. In addition to the best known macro-nutrients, sugars (carbohydrates), proteins and fats (lipids), the body also needs micro-nutrients. The latter, so called because the body only needs them in small quantities, play an essential role in the production of enzymes, hormones and other substances that help regulate the growth, activity, development and functioning of the defense system. "organism (immune system), the reproductive system and all metabolic processes.

The vitamins: organic compounds with a very different chemical structure, present in small concentrations in tissues and food. The recommended intake levels for vitamins are extremely low (read the Hoax). They are not used either as a source of energy or as a material for the construction of the structures of the organism but as "facilitators" for the performance of different functions that occur in the body. For this reason, they are indispensable for growth, for the integrity of cells and for the regular development of metabolic processes.

Classification

Classification

Vitamins can be divided into two large groups: water-soluble (which dissolve in water) and fat-soluble (which dissolve in fats).

The water-soluble vitamins (which dissolve in water), which include vitamin C, or ascorbic acid, and vitamins of group B, participate in so-called reactions of oxide reduction and / or they bind to various enzymes involved in vital metabolic processes involving sugars (carbohydrates), fats (lipids), proteins, nucleic acids (DNA, RNA) or other vitamins.

The fat-soluble vitamins (which dissolve in fats) are the A, D, E, K. They are transported inside the body by fats and are stored in the adipose tissue. Their action is more articulated and varied; in some cases, as for the vitamin D, they may also have a similar role to hormones.

Functions

Functions

The functions performed by vitamins in the body are many and differ from one to the other.

Vitamin A (or retinol)

It is a fat-soluble vitamin (dissolves in fats), so its absorption depends on the quantity and quality of fats (lipids) introduced with the diet as well as on the bile acids contained in the bile. Vitamin A is essential for growth and normal development and differentiation of the tissues that make up the organism. In particular, in addition to having an antioxidant action (ie protecting against damage caused by oxygen), it also performs many other functions:

  • intervenes in the production of proteins
  • stimulates the immune response
  • it is essential for the health of bones, teeth
  • plays a fundamental role in the vision process, in fact it is part of the components of a photosensitive protein (sensitive to light) present on the retina, responsible for the mechanisms of vision, which gives the eye sensitivity to light

Vitamin A is present in foods in two forms:

  • retinol, in animal foods, especially chicken and turkey liver, fish oil, eggs and dairy products
  • carotenes (provitamin A), also fat-soluble, of which the main representative is beta-carotene. They are abundant in yellow-orange vegetables, such as carrots, squash, peppers, peaches and melons, and in green leafy vegetables, including spinach and broccoli, but it is also present in the red (yolk) of egg and in milk and derivatives

Since vitamin A is sensitive to heat, it is good to eat raw foods whenever possible, or subject them to quick and not "aggressive" cooking.

Vitamin B

It is actually a group of eight water-soluble vitamins (which dissolve in water): B1 or thiamine, B2 or riboflavin, B3 or PP or niacin, B5 or pantothenic acid, B6 or pyridoxine, B7 or H also known such as biotin, B9 or folic acid and B12 or cyanocobalamin.

B vitamins are mainly present in:

  • Whole grains
  • foods of animal origin (meat, especially offal, shellfish, eggs, dairy products)
  • legumes
  • dried fruit
  • some green leafy vegetables, like spinach

They play a fundamental role in the body's antioxidant defenses. They intervene in:

  • sugar metabolism (carbohydrates), proteins, fats (lipids)
  • energy metabolism
  • metabolism of steroid hormones, alcohol and some xenobiotics (substances foreign to the organism both of natural origin and of chemical synthesis)
  • transmission of nerve impulses
  • functionality of all cell membranes

Therevitamin B12it differs from the others for the complexity of its chemical structure and is present exclusively in foods of animal origin. It has anti-anemic properties (that is, it acts against the reduction of hemoglobin, an important protein that plays a key role in the transport of oxygen to tissues), contributes to the production of red blood cells and the production of nucleic acids.

Its deficiency is responsible for pernicious anemia (this vitamin is in fact important for the maturation of red blood cells). It also intervenes in the metabolism of folates but above all of homocysteine, an important risk factor for the onset of cardiovascular diseases.

Vitamin C (or L-ascorbic acid)

Water-soluble vitamin (which dissolves in water), of which vegetables are very rich, serves the body for:

  • produce very important substances, such as norepinephrine (a neurotransmitter that is a substance that allows nerve cells to communicate with each other and with other cells in the body), steroid hormones, bile acids contained in the bile which are used for the absorption of fats and collagen, a protein that plays a fundamental role in the structure and functionality of many tissues such as skin, cartilage, muscle tissue
  • promote intestinal absorption of iron
  • perform a protective action in the digestive system, preventing the formation of potentially carcinogenic substances such as nitrosamines
  • play a protective role against proteins, fats (lipids) and nucleic acids (DNA, RNA), thanks to its antioxidant properties
  • regenerate oxidized vitamin E

Among the main sources of vitamin C are black currants, peppers, kiwis, strawberries, citrus fruits (read Bufala), leafy vegetables such as lettuce, rocket, radicchio and spinach.

Vitamin D

Fat-soluble vitamin (which dissolves in fats), includes two inactive forms: vitamin D2 (ergocalciferol) which is formed in yeasts and plants, and vitamin D3 (cholecalciferol) which is formed in humans and animals. active vitamin comes from both.
The fundamental role of vitamin D is to maintain the balance between calcium and phosphorus within the body. This is achieved by regulating:

  • the "absorption of calcium by the intestine
  • the elimination of calcium and phosphorus by the kidney
  • the deposition of calcium in the bone tissue ensuring adequate bone formation

The following are being studied:

  • anticancer effects
  • effects on the defense system of the organism (immune system)

Vitamin D is synthesized in the skin following direct exposure to sunlight and to a lesser extent comes from food. The coverage of its daily requirement, therefore, can be independent of the diet.
The main source is represented by fish, meat and derivatives.

Vitamin E

It is a group of compounds of which the major representative is the "alpha tocopherol, a fat-soluble vitamin (which dissolves in fats), with excellent antioxidant properties that allow it to protect tissues from free radical damage. In addition, other regulatory functions at the cellular level on the immune system and on the production of proteins guided by the information contained in the DNA are also recognized.

It is found mainly in:

  • vegetable oils, such as olive, sunflower, peanut, soy, and corn
  • wheat germ
  • dried fruits, such as walnuts, almonds and hazelnuts
  • green leafy vegetables

Its absorption is favored by fats therefore, if the source of vitamin E are vegetables, it is important to dress them with extra virgin olive oil, or combine them with other vegetables rich in lipids, such as avocado.

Vitamin E is particularly unstable to heat and it is good to take it into account when preparing food; for this reason it is preferable to consume it from uncooked food and condiments.

Vitamin K

Vitamin liposoluble (which dissolves in fats) and thermostable (heat resistant), ensures the correct production of some proteins, including osteocalcin which forms and maintains strong bones because it regulates the incorporation of calcium and phosphorus in them. , therefore, indispensable for the health of the skeleton.
In addition, it is involved in the blood coagulation mechanisms by carrying out an anti-haemorrhagic action.

The naturally occurring form of the vitamin, namely K1, is found mainly in foods of plant origin; you can take it by consuming foods such as:

  • green leafy vegetables and legumes (beans, lentils etc.)
  • smells like sage and parsley

Lower quantities are found in:

  • meat, especially chicken
  • cereals
  • dairy product
Nutritional indications

Nutritional indications

Nutritional indications

LARN - Reference levels of intake for the Italian population: VITAMINS.
Average requirement (AR): values ​​on a daily basis. (Italian Society of Human Nutrition-SINU, 2014)

LARN FOR VITAMINS: MEDIUM NEED (AR)

Children

Teenagers

 

Vit. C
(mg)

Vit. B1
(mg)

Vit. B2
(mg)

Vit. B3
(mg)

Vit. B6
(mg)

Folate

(microg)

Vit.B12
(microg)

Life
(microg)

Vit.D

(microg)

 

1-3 years

25

0,3

0,4

5

0,4

110

0,7

200

10

 

4-6 years

30

0,4

0,5

6

0,5

140

0,9

250

10

 

7-10 years

45

0,6

0,7

9

0,7

210

1,3

350

10

Males

11-14 years

65

0,9

1,1

13

1,0

290

1,8

400

10

 

15-17 years

75

1,0

1,3

14

1,1

320

2,0

500

10

Females

11-14 years

55

0,8

1,0

13

1,0

290

1,8

400

10

 

15-17 years

60

0,9

1,1

14

1,1

320

2,0

400

10

ADULTS

                   

Males

18-29 years old

75

1,0

1,3

14

1,1

320

2,0

500

10

 

30-59 years

75

1,0

1,3

14

1,1

320

2,0

500

10

 

60-74 years

75

1,0

1,3

14

1,4

320

2,0

500

10

 

≥75 years

75

1,0

1,3

14

1,4

320

2,0

500

10

Females

18-29 years old

60

0,9

1,1

14

1,1

320

2,0

400

10

 

30-59 years

60

0,9

1,1

14

1,1

320

2,0

400

10

 

60-74 years

60

0,9

1,1

14

1,3

320

2,0

400

10

 

≥75 years

60

0,9

1,1

14

1,3

320

2,0

400

10

PREGNANCY

 

70

1,2

1,4

17

1,6

520

2,2

500

10

FEEDING TIME

 

90

1,2

1,5

17

1,7

450

2,4

800

10

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 none of the vitamins are available RA relating to infants.
For pantothenic acid, biotin, vitamin E and vitamin K, scientific evidence does not allow to define RA for any of the interest groups.
Niacin is expressed as niacin equivalent (NE) as it also includes niacin of endogenous origin synthesized from tryptophan (60 mg of tryptophan = 1 mg of NE).

For folate, the reference intake levels for women of childbearing age (planning or not ruling out pregnancy) and pregnant women do not include supplements indicated for the prevention of neural tube defects.
Vit. A is expressed in μg of retinol equivalent (1 RE = 1 μg of retinol = 6 μg of beta-carotene = 12 μg of other provitamin carotenoids).
Vit. D is expressed as cholecalciferol (1 μg of cholecalciferol = 40 IU vit. D). The RA considers both food intake and endogenous synthesis in the skin.

Consumption indications and warnings

Consumption indications and warnings

The water-soluble vitamins (which dissolve in water) do not accumulate in the tissues as they are rapidly eliminated through the urine and problems related to their excess in the body are unlikely to occur. Their intake must be regular.

The fat-soluble vitamins (which dissolve in fats) are slowly eliminated and can accumulate in the tissues, particularly in the adipose tissue, causing problems with excessive dosage. In reality, it is almost impossible to take excessive quantities of it with food while this can be done by taking supplements containing fat-soluble vitamins (read the Bufala).

It is therefore advisable to pay particular attention to the consumption of supplements containing fat-soluble vitamins (which dissolve in fats).

Foods with added vitamins and minerals are governed by Regulation (EC) 1925/2006, which contains the list of permitted vitamins and minerals together with the list of their sources.

In addition, the European Food Safety Authority (EFSA) has provided scientific advice on the determination of maximum tolerable levels of intake (UL) for vitamins and minerals. These values ​​represent the maximum daily amount that can be consumed without any effects. adverse health effects in all individuals of a given population group. The ULs established by EFSA are used by the European Commission and Member States to define the maximum levels of nutrients authorized to be added to foods (fortified foods) and food supplements.

Some anticoagulant drugs, such as warfarin, exert their function by antagonizing (ie acting "against") vitamin K. People who use them are always advised to seek medical attention when taking foods and supplements containing vitamin K to avoid a decrease in pharmacological efficacy.

Bibliography

Bibliography

Rindi G, Manni R. Human Physiology. IX Edition. UTET: Milan, 2005

Italian Society of Human Nutrition (SINU). LARN 2014 - Recommended intake for the population (PRI) and adequate intake (AI): VITAMINS

Italian Society of Human Nutrition (SINU). LARN 2014 - Average requirement (AR): values ​​on a daily basis: VITAMINS

In-depth link

In-depth link

Ministry of Health. Daily intake of vitamins and minerals allowed in food supplements (rev. September 2021)

European Food Safety Authority (EFSA). Tollerable upper intake levels for vitamins and minerals

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