Vitamins, what are they?

Vitamins, what are they?

Vitamins are organic molecules that are vital for the proper functioning of the body.

The human body is unable to produce them internally in sufficient quantities; they must therefore be provided via the diet. They are mainly of plant origin (from fruit and vegetables).

Vita, life

The term 'vitamin' was coined in the early 20th century by the Polish biochemist Kazimierz Funk. It comes from the Latin vita, meaning 'life', followed by the suffix 'amin' (even though the discovery of the chemical structures of vitamins subsequently proved that they do not all contain an amino chemical group).

Etymologically, a vitamin is therefore an 'amine necessary for life'.

Although they have no energy value (they do not release any calories), they act in low doses on a large number of biological processes as co-factors to chemical reactions.

Accordingly, vitamins are considered to be vital as any deficiency in terms of intake or assimilation can lead to significant physiological disorders (e.g. scurvy, beriberi).

Essential vitamins

The 13 so-called essential families of vitamins for human beings have been classified into 2 main categories:

Hydrosoluble vitamins =
can be dissolved in water

Liposoluble vitamins = can be dissolved in fats


B vitamins (B1, B2, B3, B5, B6, B8, B9 and B12) and vitamin C

Vitamins A, D, E and K

The body holds few reserves as they are eliminated in the urine.

They are stored in the adipose tissue and the liver.

Vitamin A, or retinol

Vitamin A was the first to be discovered, which is why it bears the first letter of the alphabet! Also known as retinol, it is the vitamin of the vision, so it was also given this name due to its role in the functioning of the retina.

Where is it found?

Vitamin A exists in several forms:


The carotenoids including beta-carotene = plant origin

Retinol = animal origin
Corresponds to pro-vitamin A, which is converted in the liver into vitamin A Active form of vitamin A
Found in coloured fruit and vegetables (yellow, green, orange): carrots, sweet potato, pumpkin, peppers, apricot, mango Found in pig's liver, fish liver, egg yolk

The Recommended Daily Allowance for vitamin A is 750 µg per day for men and 650 µg per day for women.

How should it be stored?

What is it used for?

What happens if there is a deficiency?

The first signs of vitamin A deficiency are:

  • Night vision problems
  • Problems with the skin and mucosa
  • Decline in the body's natural defences
  • In children, poor growth

Vitamin B1 or thiamine

Vitamin B1 is THE vitamin for energy!
It plays an essential role in energy metabolism for the body. Its discovery dates back to the late 19th century during work on beriberi, a disease related to the consumption of husked white rice and therefore depleted in vitamin B1 (contained in the husk).

Where is it found?

The human body is unable to synthesise vitamin B1, which must be obtained via the diet.
Vitamin B1 exists in several forms:

Thiamine = inactive form
obtained via the diet
Thiamine pyrophosphate (TPP) and thiamine triphosphate
= biologically active forms of vitamin B1
Found in brewer's and baker's yeast, wheatgerm, wholegrains, whole rice, egg yolk and pork. Obtained via the conversion of inactive thiamine in the liver

The Recommended Daily Allowance for vitamin B1 is 1.5 mg per day for men and 1.2 mg per day for women.

How should it be stored?

What is it used for?

What happens if there is a deficiency?

The first signs of vitamin B1 deficiency are:

  • Intense fatigue
  • Neurological disorder (difficulties with memory and concentration)
  • Weight loss

Vitamin B2 or riboflavin

Vitamin B2 was isolated from milk, which is why it is sometimes called lactoflavin.

But vitamin B2 is more generally known by the name riboflavin, from 'ribose', a sugar of which it is composed, and 'flavus', meaning yellow in Latin, in reference to its colour. Its elimination gives urine its yellow colouration.

Where is it found?

Vitamin B2 is one of the only vitamins to be produced within the body, by the intestinal flora. However, its synthesis does not produce the required daily requirements and must be supplemented via the diet.

Foods rich in vitamin B2: soya, liver, kidney, cereals, milk, hazelnuts and walnuts

The Recommended Daily Allowance for vitamin B2 is 1.8 mg/day for men and 1.5 mg/day for women.

How should it be stored?

What is it used for?

What happens if there is a deficiency?

The first signs of vitamin B2 deficiency are:

  • Lesions in the skin and mucosa (chapped lips, eczema)
  • Eye problems
  • Dull and brittle hair and nails
  • Muscle fatigue

Vitamin B3 or niacin

Vitamin B3 was isolated in 1937 from liver extract, a food recognised for its ability to prevent pellagra, a disease that causes skin and digestive lesions which gave vitamin B3 its first name: vitamin PP, for 'pellagra preventive'.

Where is it found?

Vitamin B3 is synthesised internally by the bacteria of the intestinal flora and liver, but in insufficient quantity, hence the need for supplementation via the diet. The body produces it from an essential amino acid, tryptophan.

Vitamin B3 is found in 2 forms (not to be confused with nicotine!):

  • in acid form, nicotinic acid or niacin
  • in amide form, nicotinic amide or nicotinamide.

Foods rich in vitamin B3: yeast, liver, meat, fish, eggs, pulses.

The Recommended Daily Allowance for vitamin B3 is 17.4 mg per day for men and 14 mg per day for women.

How should it be stored?

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What is it used for?

What happens if there is a deficiency?

The first signs of vitamin B3 deficiency are:

  • Pellagra (skin disorder)
  • Digestion problems, diarrhoea
  • Fatigue

Vitamin B5 or pantothenic acid

Vitamin B5 is very widespread in nature, hence its name pantothenic acid, from the Greek 'pantos' meaning everywhere.
Its action on the nervous system and its benefits for the skin sometimes mean it is known as the anti-stress vitamin or the skin vitamin.

Where is it found?

Our intestinal bacteria produce it in negligible quantities, hence the need for supplementation via the diet.

Foods with especially high vitamin B5 content: mushrooms, offal, cabbage, eggs, yeast and royal jelly.

  • Vitamin B5 is omnipresent in our diet. Deficiencies are therefore extremely rare!

The Recommended Daily Allowance for vitamin B5 5.8 mg per day for men and 4.7 mg per day for women.

How should it be stored?



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What is it used for?

Once in the body, vitamin B5 is converted into co-enzyme A, a well-known co-factor involved in numerous bodily functions:

Vitamin B6 or pyridoxine

Vitamin B6 is certainly the best known among the B vitamins, and one of the most widely used!

Where is it found?

We talk of vitamin B6, but in fact this term covers several compounds present in our body:

  • pyridoxine (alcohol form),
  • pyridoxal (aldehyde form),
  • pyridoxamine (amine form),
  • and their active phosphorylated derivatives.

The Recommended Daily Allowance for vitamin B6 1.8 mg per day for men and 1.5 mg per day for women.

Foods rich in vitamin B6: cereals, potatoes, soya, bananas, fish, walnuts.

How should it be stored?



What is it used for?

What happens if there is a deficiency?

The first signs of vitamin B6 deficiency are:

  • Fatigue
  • Insomnia
  • Depressive state

Vitamin B8 or biotin

Vitamin B8 was discovered in the early 20th century through parallel research efforts. The first work was investigating a disease associated with a diet rich in raw egg, potentially related to a vitamin deficiency called vitamin H at the time (for 'Haut', the German word for skin, a deficiency of which leads to skin ailments). At the same time, a molecule called biotin used to lessen the symptoms of the raw egg ailment was discovered in yeast.

Vitamin H and biotin are one and the same molecule, later renamed vitamin B8.

Where is it found?

Vitamin B8 is synthesised in high quantities by the bacteria of the digestive tract.

As deficiency is both rare and benign, the Recommended Daily Allowance is very low, in the order of 0.1 to 0.3 mg per day.

Foods rich in vitamin B8: brewer's yeast, offal, egg yolk, saltwater fish, peanuts, chocolate.

How should it be stored?



What is it used for?

What happens if there is a deficiency?

The first signs of vitamin B8 deficiency are:

  • Skin lesions
  • Dermatitis
  • Hair loss

Vitamin B9 or folic acid (folates)

The term vitamin B9 covers folic acid and its derivatives, called folates. The word folate derives from the Latin 'folium', meaning leaf, as vitamin B9 is found in abundance in the leaves of certain plants, notably spinach.

It is THE vitamin for pregnant women, as it plays a vital role in foetal development. The risk of folic acid deficiency is quite high, notably during pregnancy.

Where is it found?

Folic acid is a substance synthesised by plants and micro-organisms, but not human beings, hence the need for intake via the diet.

The Recommended Daily Allowance for vitamin B9 is 330 µg per day.

Foods rich in vitamin B9: almonds, asparagus, spinach, liver, cress, lentils, wheatgerm.

How should it be stored?



What is it used for?

What happens if there is a deficiency?

The first signs of vitamin B9 deficiency are:

  • Anaemia
  • Degraded mucous membranes (diarrhoea)
  • Restricted growth
  • Depression
  • Foetal development defects

Vitamin B12 or cobalamin

Vitamin B12 was discovered during research into pernicious anaemia dating back to the period 1920s to 1950s, which doctors were unable to treat at the time. Researchers discovered that liver extract was able to cure pernicious anaemia, and they isolated a red pigment they named vitamin B12.

Vitamin B12 is the largest vitamin with the most complex structure: very close to the structure of haemoglobin (the molecule that transports oxygen in the red blood cells), its central atom is cobalt, hence the name cobalamin.

Where is it found?

The term "cobalamin" covers several forms of vitamin B12:

Natural inactive form Synthetic inactive form 2 biologically active forms
Present in the diet: meat, fish, eggs, yeast. Non-natural, via synthesis Co-enzymes resulting from the activation of the 2 inactive forms in the body

The body is unable to synthesise the cobalamins, they must therefore be obtained exclusively via the diet.

The Recommended Daily Allowance for vitamin B12 is 4 µg per day.

Over 60% of the vitamin B12 present in our body is stored in the liver, with further quantities in the brain. These reserves cover several years' requirements.

How should it be stored?



What is it used for?

What happens if there is a deficiency?

Not secreted by plants, vitamin B12 can only be obtained from animals or bacteria, which explains deficiencies in those following a strict vegetarian diet.

The first signs of vitamin B12 deficiency are:

  • Anaemia
  • Fatigue
  • Psychological and cognitive imbalance
  • Degradation of the myelin sheath (tingling, diminished sensorial perception)

Vitamin C or ascorbic acid

Vitamin C owes its name of ascorbic acid to the disease of scurvy, which had affected sailors since antiquity. Caused by a lack of fresh produce in the diet, it leads to gum disease, ruptures in the small blood vessels, haemorrhaging and bone pain. In the 18th century, a doctor discovered the effectiveness of lemon juice in the prevention of scurvy. But it was only in 1928 that the active substance was isolated and named vitamin C, in reference to citrus.

Where is it found?

Ascorbic acid is synthesised by plants and numerous animals, but not human beings. It must therefore be obtained via the diet.

The Recommended Daily Allowance for vitamin C is 110 mg/day.

Foods rich in vitamin C: acerola, kiwi fruit, citrus fruit, peppers, parsley, blackcurrant, cabbage, cress, sprouted seeds.

How should it be stored?



What is it used for?

What happens if there is a deficiency?

1000 mg to 2000 mg of vitamin C is stored in the body, but these reserves will be used in 2 to 3 weeks if not supplemented.

The first signs of vitamin C deficiency are:

  • Fatigue
  • Bleeding gums
  • Reduced resistance to infection
  • Vein problems

Vitamin D or calciferol

Vitamin D is the sunshine vitamin! Its discovery is associated with rickets, a disease affecting bone calcification in children in regions with low sunlight. In the early 19th century, doctors discovered the preventive and curative properties of cod liver oil against rickets. Vitamin D was only isolated in the 20th century.

Where is it found?

The term vitamin D actually covers several molecules derived from sterols (cholesterol family).

In humans there are several forms of vitamin D:

Vitamin D2 = ergocalciferol Vitamin D3 = cholecalciferol Calcitriol
Inactive form Inactive form Active form, activates biological functions
by binding to its receptor in the cell nucleus
Produced by plants Sourced from animals and internally (produced by the body) Vitamin D2 or D3 converted in the liver and kidneys into active form

The Recommended Daily Allowance for vitamin D is 15 µg per day.

Foods rich in vitamin D: fish, eggs, cheese, liver.

In addition to dietary intake, most vitamin D is produced by the body internally in the form of vitamin D3. 
Ultraviolet rays on the skin activate the formation of vitamin D3 from a derivative of cholesterol naturally present in the body. Vitamin D is therefore considered to be a real vitamin as humans are able to produce it themselves, but rather in the form of a steroid hormone. Liposoluble, vitamin D is stored in fats.

How should it be stored?



What is it used for?

What happens if there is a deficiency?

Vitamin D deficiency its currently recognised as a pandemic. In France, 80 % of the population is affected. In fact, few foodstuffs contain it and are not sufficient to cover requirements, especially in winter when sunshine levels are lower.

The first signs of vitamin D deficiency are:

  • Reduction in muscle tone
  • Fatigue
  • Bone deficiency