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Vitamin D


Vitamin D is a fat-soluble hormone and exists mainly in two forms in humans: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).

Vitamin D2 comes exclusively from the diet (mushrooms for example). Vitamine D3 comes either from the diet (fish, eggs…) or is synthesized by the body.

The major source of vitamin D present in the body is cholecalciferol (vitamin d3) synthesized in the skin from cholesterol through a chemical reaction that is dependent on sun exposure (specifically UVB radiation)

What are the benefits of Vitamin D?

Vitamin D  is essential for all ages:

– it is necessary for the normal absorption and utilization of calcium and phosphorus, thus ensuring optimal bone and teeth health;
– it contributes to the normal function of the immune system;
– and, it plays a role in the process of cell division.

Vitamin D deficiencies – Some Figures:

According to national surveys in the UK, across the population, approximately 1 in 2 people have low vitamin D levels – defined as serum levels below 50 nmol/L: when levels of 75 nmol/l are considered optimal. (SACN)

In France, 80% of the population is vitamin D deficient (levels below 75 nmol /l) (Vernay 2006-07)

In Belgium, 95% of patients do not reach the optimal value (75 nmol /l). (Daoudi 2009)

Therefore, it is crucial to increase vitamin D levels in the population with low vitamin D levels.

What are the main risk factors for vitamin D deficiency?

Vitamin D deficiency is often related to insufficient exposure to the sun.

Other risk factors are:

– Age: Older people have a reduced ability to synthesize vitamin D in the skin when exposed to UVB radiations (sun) and are more likely to stay indoors or use sunscreen, which prevents vitamin D synthesis (Holick, 2011)

– Skin pigmentation: Melanin reduces vitamin D synthesis. People with darker skin require longer UVB exposure to produce the same amount of vitamin D as those with a lighter skin tone.

– Geographical location and seasons: Geographical location influences vitamin D levels because people living further away from the equator do not get enough sunlight (UVB). In winter and in areas north of the 40th parallel (for people living in the northern hemisphere) the number of photons reaching the Earth’s surface is significantly reduced, and hence reducing vitamin D synthesis.

During the winter period, people living north of the 40th parallel (north of the Madrid-Naples line), are probably not sufficiently exposed to the sun to meet their vitamin D needs.

An American study shows that during the summer and at noon, 3 to 8 minutes of sun for people with slightly tanned skin and exposing 25% of their skin, are sufficient to produce 400 IU of vitamin D in the city of Boston (located at the 42nd parallel). In winter, on the other hand, it is almost impossible for these same persons to synthesize vitamin D. (Terushkin, 2010)

– Lifestyle: Today, most Westerners spend most of their time indoors (house, office, car etc ..)  resulting in significant vitamin D deficiencies. This can only be offset by the daily intake of a vitamin D dietary supplement.

– Sun protection:  Sun protection such as shade, sun-protective clothing, and the application of sunscreens, hinder the exposure of the skin to the sun’s rays and lead to a decrease in vitamin D synthesis. The application of Sun cream (2 mg/cm2) with a sun protection factor (SPF) of 10 reduces UVB radiation by 90% (Balk, 2011).

CAUTION: The risk of skin cancer increases when people overexpose themselves to the sun and intentionally present themselves to artificial UV sources.

– Overweight and obese people: Vitamin D is fat soluble and is stored in the body fat. Obese and overweight people may thus need two to three times more vitamin D than others.

– Breastfed babies: Daily intake of vitamin D is recommended in breastfed infants. Another alternative is that the mother takes vitamin D supplement to indirectly enrich breast milk.


There are various forms of vitamin D but the best known are vitamin D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D2 is found mainly in plants. Vitamin D3 is mainly of animal origin except for the one that we propose that comes from lichen.

Vitamin D2:

– mushrooms (chanterelles contain about 5 mcg or 200 IU vitamin D2 per 100 grams)

Vitamin D3:

– Fish liver oil: 1 large spoon of 15 ml brings about 34 mcg or 1360 IU

– Fish (salmon, mackerel, tuna, sardines …): between 3 mcg or 120 IU and 19 mcg or 760 IU per 100 grams

– Dairy products fortified with vitamin D3

– The egg yolk: about 3 mcg or 120 IU per 100 grams

– Beef liver: maximum 5 mcg or 200 IU per 100 grams

– And lichen!


Vitamin D3 is the most assimilable, effective form and is the form synthesized by the body (endogenous)

Vitamin D3 passes twice as well in the blood (Tripkovic, 2012) and is much more effective than vitamin D2 (Heaney, 2011, Armas, 2004).

There, it is preferable to take a supplement rich in vitamin D3.


Armas LA, Hollis BW, Heaney RP. Vitamin D2 is much less effective than vitamin D3 in humans. J Clin Endocrinol Metab. 2004 Nov;89(11):5387-91
Balk SJ; Council on Environmental Health.; Section on Dermatology.. Ultraviolet radiation: a hazard to children and adolescents.Pediatrics. 2011 Mar;127(3):e791-817.

Daoudi 2009 Evaluation de la carence en vitamine D chez des patients hospitalisés à Bruxelles. Rev. Med. Brux

Heaney RP, Recker RR, Grote J, Horst RL, Armas LA. Vitamin D(3) is more potent than vitamin D(2) in humans. J Clin Endocrinol Metab. 2011 Mar;96(3):E447-52.

Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP, Murad MH, Weaver CM; Endocrine Society.. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011 Jul;96(7):1911-30.

SACN – Vitamin D and Health report:

Schmid A, Walther B. Natural vitamin D content in animal products. Adv Nutr. 2013 Jul 1;4(4):453-62.

Terushkin V, Bender A, Psaty EL, Engelsen O, Wang SQ, Halpern AC. Estimated equivalency of vitamin D production from natural sun exposure versus oral vitamin D supplementation across seasons at two US latitudes. J Am Acad Dermatol. 2010 Jun;62(6):929.e1-9.

Tripkovic L, Lambert H, Hart K, Smith CP, Bucca G, Penson S, Chope G, Hyppönen E, Berry J, Vieth R, Lanham-New S. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clin Nutr. 2012 Jun;95(6):1357-64.

Vernay M. et al. “Statut en vitamine D de la population adulte en France : l’étude nationale nutrition santé (ENNS, 2006-2007)”.