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Vitamin D3 in the eye of science

Calcitriol – pleiotropic action, supplementation recommendations.

Vitamin D3 enjoys great interest among researchers due to its multifaceted action. The knowledge about the function that it can perform in the human body is constantly deepened.

Vitamin D3

Physiological vitamin D3 is synthesized in the human body under the influence of UVB radiation from 7-dehydrocholesterol, which is produced in the liver from cholesterol.

The biologically active form of vitamin D3 is 1,25-dihydroxy-cholecalciferol (1,25 (OH) 2D3, calcitriol), which binds to intracellular receptors found on many types of cells and is responsible, according to scientific reports, for the expression of over 2,000 genes, hence its pleiotropic action [1,2]. Specific cytosolic receptors are found on the epithelial cells of the kidneys, intestines, and osteocytes, keranocytes, fibroblasts, monocytes, macrophages, and active B and T lymphocytes [3]. Due to the multidirectional participation of vitamin D3 in metabolic pathways, its role in the pathogenesis of neoplastic and autoimmune diseases (type 1 diabetes, multiple sclerosis), as well as strokes, bronchial asthma, AD, obesity can be traced. Moreover, its correct concentration will contribute to the reduction of the risk of osteoporosis, osteomalacia, rickets and fractures [1, 4, 5]. In cardiovascular diseases, there is a correlation between low vitamin D3 levels and the occurrence of arterial hypertension. It is associated with the reduction of the expression of the gene encoding renine, and as a consequence, the functioning of the RAA system is disturbed [6]

The correlation between the occurrence of mood disorders and insufficient exposure to sunlight is well known. The results of many studies clearly show a close relationship between low calcitriol levels and the prevalence of mental illnesses (depression, neurosis, bipolar disorder). It has been proved that 1,25 (OH) 2D3 activates the expression of the enzyme tyrosine hydroxylase, which participates in the synthesis of catecholamines, increasing the production of dopamine, noradrenaline and adrenaline, which play a key role in the CNS [7].

The main source of vitamin D3 is cutaneous synthesis, but it can be supplied exogenously with food. Fatty fish (salmon, mackerel, tuna) are a rich source of the active form of cholecalcitriol

The extent to which we should supplement vitamin D3 depends on the climatic zone, the level of sunlight, and individual factors (age, weight).

Guidelines for vitamin D3 supplementation (based on the Resolution of the Team for Dietary Supplements of 22 May 2019 on the expression of an opinion on the maximum dose of vitamin D in the recommended daily dose in dietary supplements)


Recommended doses of vitamin D (IU / day) depending on body weight and vitamin D intake throughout the year.


Newborns (0-12 months)

400 (from the first days of life to 6m),

400-600 (between 6-12 months)

Children (1-10 years)


in healthy people staying in the sun with uncovered forearms and lower legs for at least 15 minutes from 10.00 to 15.00, without sunscreen in the period from May to September – supplementation is not necessary

Youth (11-18 years)


Adults (19-65 years old)


Seniors (> 65-75 years) and people with dark skin


Due to the reduced effectiveness of skin synthesis, vitamin D supplementation is recommended throughout the year

Oldest seniors (> 75 years old)


Pregnant and lactating women

if it is not possible to assess the vitamin D concentration in the blood (on the basis of the 25 (OH) D metabolite), it is recommended to use vitamin D at a dose of 2000 IU / day during pregnancy and lactation.

it is recommended that vitamin D levels be routinely tested before and during pregnancy in order to maintain optimal concentrations in the range> 30-50 ng / ml

Guidelines for optimal calcidiol concentrations and vitamin D supplementation vary across European countries:

  • The Scandinavian countries (Denmark, Finland, Iceland, Norway and Sweden) have set a target serum 25 (OH) D concentration of ≥20 ng / ml [8], a similar threshold for 25 (OH) D has been adopted in Germany, Austria and Switzerland [ 9].
  • In the guidelines for Central Europe, 25 (OH) D concentration of 30–50 ng / ml was considered optimal to ensure all health benefits [10].

Recommended preparations
There are many dietary supplements available in Poland that contain metabolites of vitamin D3, while the drugs are, for example:


You should remember about the possibility of consulting with a doctor who, depending on the patient’s health condition, will individually determine the appropriate dosage of vitamin D and recommend appropriate preparations

  1. Pludowski, MF. Holick, WB Grant, Vitamin D supplementation guidelines, J. Steroid Biochem Mol Biol. 2018; 175: 125–135.
  2. Haussler, PW. Jurutka, M. Mizwicki, Vitamin D receptor (VDR)-mediated actions of 1a, 25(OH)2 vitamin D3: genomic and non-genomic mechanisms. Best Pract Res Clin Endocrinol Metab, 2011
  3. Mutschler, G. Geisslinger, H. K. Kroemer, P. Ruth, Mutschler Farmakologia i toksykologia.
  4. Pludowski , MF. Holick, S. Pilz, Vitamin D effects on musculoskeletal health, immunity, autoimmunity, cardiovascular disease, cancer, fertility, pregnancy, dementia and mortality-a review of recent evidence. Autoimmun Rev. 2013
  5. Souberbielle, JJ. Body, JM. Lappe, Vitamin D and musculoskeletal health, cardiovascular disease, autoimmunity and cancer: recommendations for clinical practice. Autoimmun Rev, 2010
  6. B. Grant, M.F Holick, Benefits and requirements of vitamin D for optimal health: A review. Altern. Med. Rev., 2005.
  7. Stefanowski, A. Antosik-Wójcińska, Ł. Święcicki, Wpływ niedoboru witaminy D3 na poziom nasilenia objawów depresyjnych. Przegląd aktualnych badań, Psychiatr. Pol. 2017; 51(3): 437–454
  8. Nordic Council of Ministers. Integrating Nutrition and Physical Activity. 5th ed. Norden, Copenhagen, Denmark: 2012. Nordic Nutrition Recommendation 2012.
  9. Spiro, JL. Buttriss, Vitamin D: An overview of vitamin D status and intake in Europe. Nutr Bull. 2014
  10. Rusińska, P. Płudowski, M. Walczak i inni, Rekomendacje zasady suplementacji i leczenia witaminą D – Nowelizacja 2018 r.
  11. Marcinkowska, A. Mickiewicz, M. Fijałkowski, Plejotopowe działanie witaminy D, Choroby Serca i Naczyń 2019, tom 16, nr 1, 45–52,

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