1. What is vitamin D ?

Vitamin D is a fat-soluble vitamin that is important for the normal functioning of the human body. However, it is considered more of a hormone than an essential vitamin, because it can be produced in sufficient quantities in the human body under certain conditions: exposure to UV rays from sunlight and a diet rich in vitamin D (1).

2. What forms of vitamin D are there?

There are two forms of vitamin D: vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) (1).

3. How are forms of Vitamin D produced?

The production of vitamin D3 in the human body depends on the skin's exposure to ultraviolet rays in sunlight. With exposure to the sun, the skin converts the precursor of vitamin D3 (7-dehydrocholesterol) into vitamin D3 (cholecalciferol). The amount produced depends on the person's age, time of day of sun exposure, tone and amount of uncovered skin, and whether or not sunscreen is used.

The production of vitamin D2 (ergocalciferol) depends on the intake of its precursor (ergosterol), as it does not exist naturally in the human body. This precursor exists in mushrooms and should therefore be included in the human diet.

4. How can you acquire vitamin D?

Unfortunately, vitamin D is found in very few foods in nature. They include fish liver oils, some fatty fish (salmon, sardines, mackerel, tuna), liver (beef), mushrooms and egg yolks.

Vitamin D can also be obtained from vitamin D-fortified foods on the market, such as orange juice, milk, cereals and dietary supplements (2).

5. What are the health benefits of Vitamin D?

Vitamin D is essential for the fulfillment of multiple functions that the human body needs to perform daily, which include:

  • Helps the body absorb calcium and regulates calcium and phosphorus levels in the blood, which support cellular processes, neuromuscular function and bone ossification.
  • Influences cell growth and development.
  • Helps with the functioning of the immune system.
  • It helps in the secretion of insulin by the pancreas (thus controlling sugar levels) and prolactin by the pituitary gland.
  • Helps regulate collagen and magnesium metabolism.
  • It may reduce the risk of developing breast and bowel cancer.
  • It can reduce the risk of developing autoimmune diseases such as diabetes, multiple sclerosis, rheumatoid arthritis and lupus.

6. What are the symptoms of vitamin D deficiency?

In adults, a lack of vitamin D can cause subtle symptoms such as: mood changes, depression, tiredness, fatigue, muscle and bone pain (especially in the back), high blood pressure and recurrent flu and colds.

7. Who should take vitamin D supplements?

 According to data from the National Health and Nutrition Examination Survey (NHANES) in the United States of America, it is estimated that one billion people around the world are deficient or insufficient in vitamin D.

This large number of people affected is due to the reduced number of foods naturally rich in vitamin D (making it difficult to ingest the necessary amount of vitamin D even through a varied and balanced diet) and little sun exposure in the autumn months. it's winter.

Several European health systems advise the consumption of a vitamin D supplement for all children over 4 years of age, adults and pregnant women during the autumn and winter months.

8. How important is it to combine vitamin K2 with a vitamin D supplement?

Vitamin D, vitamin K2 and calcium work together and depend on sufficient amounts of each to function optimally.

Vitamin D in combination with a lack of vitamin K2 can cause overabsorption of calcium in inappropriate places - blood vessels and the kidneys, which can cause vascular disease (stiffness) and kidney stones (stones). Vitamin K2 keeps calcium in the right places, that is, in the teeth and bones and out of soft tissues and arteries.

9. What are the adverse effects of taking too much vitamin D?

It is important to monitor vitamin D levels in your blood if you take vitamin D supplements for a long time (> 6 months). Taking a dose greater than 4000 IU (or 100mcg) per day is not recommended.

Excess vitamin D in the body can increase calcium levels (hypercalcemia) which can lead to weakening of bones and damage the kidneys and heart.

If these symptoms appear, taking the supplement should be stopped immediately.


1. S. Department of Health and Human Services, National Institutes of Health, Office of Dietary Supplements. Vitamin D. Updated November 09, 2018.

2. Roseland JM, Phillips KM, Patterson KY, Pehrsson PR, Taylor CL. Vitamin D in foods: An evolution of knowledge. Pages 41-78 in Feldman D, Pike JW, Bouillon R, Giovannucci E, Goltzman D, Hewison M, eds. Vitamin D, Volume 2: Health, Disease and Therapeutics, Fourth Edition. Elsevier, 2018.

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