The Complete Guide to Understanding the Role of Vitamins


Non-energetic and very diverse, vitamins are among the substances that the human body is not able to synthesize or at very low doses only. Impossible to do without, however, they remain essential to maintain our vital balance since they alone allow the cells to draw the necessary energy contained in nutrients!

As a result, vitamins act on growth, good hormonal health, or enzymatic reactions, among many other different roles. Present in the number of 13, we will make the difference between fat-soluble vitamins (A, D, E, and K), stored by the body (soluble in fats), and water-soluble vitamins, which are not (soluble in water).

And these famous vitamins, where to find them precisely? And well in the diet mainly, with great reinforcement of consumption of fruits and vegetables in particular. The advantage is that they remain active even at low doses.

What we find, however, is that the modern lifestyle associated with pollution or lack of sun tends to increase our need for vitamins, while intensive production methods lead to a decrease in their content in food.

Thirteen vitamins

Each vitamin has its specificities and daily needs will vary from one individual to another! The elderly or convalescent, pregnant or lactating women, adolescents, and athletes should be particularly attentive to their daily intake, as well as people who have opted for special diets, whether it is a thoughtful diet or food supplements.

There are 13 vitamins, all of which play an important role in our body:

  1. Vitamin A or retinol
  2. Vitamin B1 or thiamine
  3. Vitamin B2 or riboflavin
  4. Vitamin B3 or niacin
  5. Vitamin B5 or pantothenic acid
  6. Vitamin B6 or pyridoxine
  7. Vitamin B8 or H or biotin
  8. Vitamin B9 or folic acid
  9. Vitamin B12 or cobalamin
  10. Vitamin C or ascorbic acid
  11. Vitamin D or calciferol
  12. Vitamin E or tocopherol
  13. Vitamin k

Vitamin A

Type: Fat-soluble.

The first vitamin to be discovered, vitamin A is particularly recognized for its key role in the functioning of eyesight.

Heat resistance but easily altered by air or light, a large part of the daily intake of vitamin A remains stored in the liver to meet the needs of the body for 1 to 2 years.

What role for vitamin A?

Vitamin A acts on many different levels, from the proper development of bones and teeth to the normal functioning of the thyroid gland and up to cell multiplication allowing the formation of skin tissues.

Particularly effective at eye level, it plays a key role in distinguishing shapes in the dark. It will also be researched for its action against infections since it contributes to the maintenance of immune defenses.

Where to find vitamin A?

In its natural state (retinol) vitamin A exists in products exclusively of animal origin while it is rather in plants that it will be found in the form of provitamin A (beta-carotene).

  • Fish liver oils.
  • Fish liver.
  • Calf liver.
  • Oysters.
  • Butter, margarine.
  • Milk.
  • Camembert.
  • Vegetables (carrot, cabbage, peppers, pumpkin, spinach, potatoes).
  • Fruits (raspberries, apricots, oranges, melons).

Vitamin A deficiencies, what are the risks?

Night blindness, clouding of the cornea, dryness of the conjunctiva, avitaminosis, or vitamin A deficiency, will result in visual disturbances. To this may be added various capillary, respiratory or digestive problems due to impaired cell renewal.

Vitamin B1 – Thiamine

Type: Water-soluble.

Essential for the good health of the body’s metabolism, vitamin B1 mainly influences the secretion of energy from proteins, carbohydrates and fats ingested.

What role for vitamin B1?

Beyond its nutrient-synthesis action, vitamin B also ensures the proper functioning of the nervous system and has beneficial effects on mood changes, memory, and concentration. Reputed to be an aperitif, it is particularly recommended to stimulate appetite in case of eating disorders but also in the treatment of neuropsychiatric dysfunctions related to alcoholism, thanks to its oxidative action.

Where to find vitamin B1?

It is in cereals that it is most common to encounter vitamin B1, but also in:

  • Oatmeal.
  • Brewer’s yeast.
  • Pulses.
  • Dried fruits.
  • Vegetables (cabbage, asparagus, potatoes).
  • Meat (pork, chicken).
  • Eggs
  • Liver.

Vitamin B1 deficiencies, what are the risks?

A vitamin B1 deficiency will most of the time result in increased fatigue and irritability as well as significant weight loss related to loss of appetite.

Note also some vision disorders, some concentration problems as well as the possible appearance of muscle weakness more commonly known as polyneuritis.

Vitamin B2 – Riboflavin

Type: Water-soluble.

The action of vitamin B2 crystallizes around 2 main axes. The production of energy on the one hand, through the synthesis of nutrients, and the production of keratin, so essential to the good health of the skin.

What role for vitamin B2?

Through the synthesis of nutrients and the oxidation of glucose, vitamin B2 participates in providing the whole body with energy, thus ensuring the growth of the youngest and the body’s resistance to external aggressions.

Present in particular in the retina where it promotes vision in the dark, it also acts on the elasticity of the skin and hair, by the secretion of keratin.

Where to find vitamin B2?

Key sources include:

  • Brewer’s yeast.
  • Soybeans.
  • Offal.
  • Meats.
  • Oily fish.
  • Whole grains.
  • Legumes.
  • Dried fruits.
  • Milk.
  • Soft cheeses.

Among the plants, we will bet mainly on spinach, carrots, mushrooms, lettuce, or avocado.

Vitamin B2 deficiencies, what are the risks?

A lack of riboflavin will generally result in an overall decrease in tone and skin manifestations giving rise to significant dryness and cracks in the lips in particular. Eye disorders also include loss of night vision and increased sensitivity to light.

Vitamin B3 – Niacin

Type: Water-soluble.

Very close to vitamin B2, vitamin B3 also participates in the production of energy and keratin for the body. However, it is distinguished by its action on the blood and cholesterol.

What role for vitamin B3?

While it shares the characteristics common to all vitamins of group B, vitamin B3 is distinguished by its restorative action on damaged DNA and its contribution to the manufacture of hemoglobin. Important for memory, it also acts positively on the nervous system.

Where to find vitamin B3?

Contained largely in foods such as brewer’s yeast and offal, vitamin B3 is also found in:

  • Meats.
  • Oily fish.
  • Legumes.
  • Sprouted seeds.
  • Vegetables (avocado, mushrooms, peppers, cabbage …).
  • Fresh fruit.
  • Roasted peanuts.
  • Dried fruits.
  • Chocolate.
  • Dairy products.
  • Eggs.

Vitamin B3 deficiencies, what are the risks?

Mild vitamin B3 deficiencies usually result in general fatigue, headaches, dizziness, and loss of sleep and/or appetite. In the longer term may appear skin redness, photosensitivity, nervous disorders, or inflammation of the tongue.

Vitamin B5 – Pantothenic acid

Type: Water-soluble.

Vitamin B5 is inseparable from the proper functioning of cells, skin, and hair. Because the body retains only a tiny portion, it will be essential to draw it from the source, from many different foods.

What role for vitamin B5?

Anti-infectious, healing, vitamin B5 plays a key role in cell renewal and the proper functioning of the nervous system. If it participates little in the synthesis of nutrients as do the other vitamins of its group, it is found at the heart of the health of the skin and hair.

Where to find vitamin B5?

Vitamin B5 is found in many foods of animal origin, including:

  • Meats.
  • Fish.
  • Offal.
  • Eggs.
  • Dairy products.

On the plant side, we will turn mainly to green vegetables, mushrooms, avocado, or corn but also whole grains or pulses.

Vitamin B5 deficiencies, what are the risks?

Without pathology generating risks (cancer, diabetes, alcoholism …), vitamin B5 deficiencies may be due to too much consumption of highly processed products such as prepared dishes.

Vitamin B5 deficiency can then manifest itself in the form of skin, nervous, digestive, or respiratory disorders, numbness of the limbs, and significant loss of appetite.

Vitamin B6 – Riboflavin

Type: Water-soluble.

Essential for the assimilation of proteins from the diet, vitamin B6 is probably the best known of the B group. It is often found in the treatment of stress or fatigue, in addition to magnesium whose action significantly improves.

What role for vitamin B6?

Insulin synthesis, secretion of adrenaline, dopamine, serotonin, development of certain sex hormones, thank you vitamin B6! A source of energy, of course, is also involved in the production of hemoglobin and is essential for glycogenolysis, a complex process by which the liver manages to supply glucose to all organs when the blood sugar level is too low.

Where to find vitamin B6?

Here again, the sources of vitamin B6 are rich and varied with:

  • Meats.
  • Oily fish.
  • Cooked tuna.
  • Offal.
  • Vegetables (broccoli, carrots, spinach).
  • Bananas.
  • Prunes.
  • Legumes.
  • Seeds and whole grains.
  • Oatmeal.
  • Nutritional yeast.

Vitamin B6 deficiencies, what are the risks?

A deficiency of this type can lead to different ailments already known to other vitamins of the same group: nervous disorders, lesions around the eyes and mouth, loss of appetite, decreased immunity but also disorders in the liver and blood disorders.

Vitamin B8 – Biotin

Type: Water-soluble.

Largely synthesized by the body, vitamin B8 draws the rest of its source from many foods. It actively contributes to the assimilation of fats and carbohydrates as well as to the good health of the skin and hair.

What role for vitamin B8?

At the synthesis level, vitamin B8 plays a key role in the assimilation and transformation of sugar, fatty acids, and certain amino acids.

It is also found in the immune system, which ensures the proper functioning of.

Where to find vitamin B8?

Vitamin B8 is mainly concentrated in:

  • Yeasts.
  • Offal.
  • Eggs.
  • Oysters.
  • Wholemeal bread.
  • Legumes.

It is also found in variable doses in some fruits and vegetables such as avocado, mushrooms, beans, strawberries, bananas.

Vitamin B8 deficiencies, what are the risks?

Vitamin B8 deficiencies most often result in very high fatigue, digestive, psychological and neurological disorders, and skin lesions.

Eventually, tingling sensations, coordination disorders and hallucinations associated or not with depression may occur.

Vitamin B9 – Folates

Type: Water-soluble.

Very much in demand in the context of pregnancy, in particular, vitamin B9 participates in the reconstitution of damaged DNA, growth, and proper functioning of the nervous system, which earns it to be regularly used in therapeutic use.

What role for vitamin B9?

Very active in cell reproduction, vitamin B9 intervenes in the synthesis of nutrients to nourish energy to the whole body. While participating in the formation of red blood cells, it is still at the levels of the central nervous system and DNA that it is found.

Where to find vitamin B9?

Major sources of vitamin B9 include:

  • Livers.
  • Soybeans.
  • Yeasts.
  • Legumes.
  • Whole grains.
  • Eggs.
  • Fermented cheeses.
  • Vegetables (spinach, broccoli, asparagus, mushrooms, avocado).
  • Red fruits.
  • Nuts.

On the cooking side, vitamin B9 is extremely sensitive to heat so we prefer vegetables that are barely cooked or even totally raw.

Vitamin B9 deficiencies, what are the risks?

Vitamin B9 deficiencies are particularly favored during certain specific periods when needs are increased such as adolescence, pregnancy, or in case of smoking, chronic alcoholism. We can then expect certain psychological or digestive disorders, anemia, headaches, and lesions in the skin and nails.

Vitamin B12 – Cobalamin

Type: Water-soluble.

Rare for a water-soluble vitamin, vitamin B12 is stored in the body!

Essential to energy intake, it is also believed to have detoxifying, analgesic, and antidepressant properties.

What role for vitamin B12?

Thanks to its positive action on the myelin sheath, which protects nerves, vitamin B12 acts on the functioning of the nervous system. A key element in the body’s energy production, it is finally involved in the reproduction of cells and the formation of red blood cells, making it an extremely powerful anti-anemic.

Where to find vitamin B12?

Vitamin B12 is found almost exclusively in animal products, namely:

  • Meats.
  • Offal.
  • Oily fish.
  • Crustaceans.
  • Eggs.
  • Cheeses.

It is also found in rare products of plant origin such as algae or sauerkraut, in extremely small quantities.

Vitamin B12 deficiencies, what are the risks?

Among the possible main effects of vitamin B12 deficiency is the appearance of allergies or anemia resulting in intense fatigue, mood disorders, and loss of appetite. Some muscle pain, inflammation of the tongue, and a decrease in immune defenses are also possible.

Vitamin C

Type: Water-soluble.

Widely contained in fruits and vegetables, vitamin C is especially recommended by doctors as winter approaches. Recognized for its anti-fatigue action, it also acts effectively against small everyday disorders and cardiovascular diseases.

What role for vitamin C?

The functions of vitamin C include the production of collagen essential for tissue reconstruction, the renewal of white blood cells, and the strengthening of the immune system, which makes it particularly effective in the fight against microbial infections.

Essential in the assimilation of calcium and iron by the body, vitamin C is also an excellent antioxidant.

Where to find vitamin C?

Vitamin C is found in abundance in the daily diet, provided you rely heavily on fresh fruits and vegetables with:

  • Red pepper, cabbage, raw spinach, broccoli, asparagus, beans, peas, parsley.
  • Kiwi, citrus, red fruits, some exotic fruits.
  • Sprouted seeds.
  • Meats.
  • Oily fish.
  • Offal.

Pay attention here again to the cooking of food.

Vitamin C deficiencies, what are the risks?

Vitamin C deficiencies are rather common and can result in skin disorders, great fatigue, or greater vulnerability to everyday aggressions.

In the most severe cases, a vitamin C deficiency can lead to scurvy usually characterized by various hemorrhages; muscle degeneration, and joint pain.

Vitamin d

Type: Fat-soluble.

Essential for calcium fixation, vitamin D is mainly produced by the body, thanks to sunlight. The rest of the intakes can be easily found in the diet.

vitamin D

What role for vitamin D?

Mainly known for the key role it plays in the consolidation of bones and teeth via the absorption of calcium and phosphorus, it is also essential for blood stimulation and cardiac regulation.

An adequate intake of vitamin D will help prevent certain autoimmune diseases, or Alzheimer’s or Parkinson’s disease.

Where to find vitamin D?

Some foods will supplement the recommended intakes, including:

  • Fish liver oils.
  • Oily fish.
  • Offal.
  • Eggs.
  • Cheeses.

Vitamin D deficiencies, what are the risks?

Vitamin D deficiency can be caused by a variety of factors, the main one usually being insufficient sun exposure in winter or in areas of the world where less sunlight is available. If it can sometimes be serious, it is because it leads to demineralization of bones and teeth recognizable by pain, deformation of the spine, and even spontaneous fractures.

Vitamin e

Type: Fat-soluble.

Essential for cell growth and reproduction, vitamin E is also involved in the eyesight, skin, or immune system. It is usually combined with vitamins A and C to form the antioxidant cocktail ACE which has already been widely proven.

What role for vitamin E?

As an antioxidant, vitamin E acts positively in the prevention of certain cancers and cardiovascular diseases but also in slowing down the aging of the skin, eyesight and prostate. It also helps to strengthen the immune defenses and fight against bad cholesterol.

Where to find vitamin E?

Vitamin E is found especially in vegetable oils (wheat germ, hazelnut, walnut, sunflower avocado …) but also in:

  • Butter.
  • Eggs.
  • Oilseeds
  • The liver.
  • Oily fish.
  • Mussels.
  • Some green vegetables (broccoli, Brussels sprouts, watercress).

Vitamin E deficiencies, what are the risks?

During a vitamin E deficiency, there will usually be some muscle weakness, partial loss of vision, and some coordination difficulties. Vitamin E participates in the protection of the sheaths surrounding neurons. An insufficient amount will tend to impair the functioning of the nervous system.

Vitamin k

Type: Fat-soluble.

Produced 80% by the body, vitamin K occupies a fundamental place in blood clotting and bone mineralization. This is why medicine regularly uses it, especially for newborns who sometimes lack it at birth.

What role for vitamin K?

Vitamin K exists in two different forms, vitamin K1, and vitamin K2, the latter mainly involved in bone mineralization.

Essential for proper cellular functioning, it is recognized mainly for its positive action on coagulation.

Where to find vitamin K?

Foods of plant origin are particularly rich in vitamin K with:

  • Endives.
  • Raw spinach.
  • Broccoli.
  • Asparagus.
  • Cabbages.
  • Green beans.
  • The green salad.

Vitamin K2, on the other hand, is mainly present in animal products such as liver oils and dairy products.

Vitamin K deficiencies, what are the risks?

Rather rare in adults, vitamin K deficiencies significantly alter the clotting process, which can result in spontaneous bleeding, the appearance of bruises, heavy periods, or internal bleeding in the most severe cases.

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