Vitamin D plays an essential role in strengthening the immune system. They exist in two main forms: D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D2 is mainly produced by plants and vitamin D3 is mainly of animal origin (cod liver oil, oily fish, etc.) with the exception of certains lichens.

Lichens, and more particularly that of the genus Cladonia (Family Cladoniaceae) is the only plant known to date to produce vitamin D3 due to its unique symbiosis resulting from the association of a microscopic alga and a filamentous fungus. This plant has the unique capacity to synthesise vitamin D3 from the pro-vitamins 7-DHC and ergosterol at low temperatures (<16°C).  

The harvest of this lichen is eco-responsible, harvested by hand, in the wild and following the natural cycle of development of this plant.

Without supplementation, the main source of vitamin D remains the sun's UV rays, where vitamin D is then synthesised by the skin. Vitamin D is therefore the sun's vitamin par excellence. However, during the non-summer period, when exposure to the sun is less frequent and vitamin D intake from food alone is insufficient, vitamin D deficiency can occur. According to the French Academy of Medicine, 41% of the French population lacks vitamin D in winter.

In addition to weakening the immune system, a lack of vitamin D can also lead to brittle bones, poor cell division and mood swings due to the slower production of serotonin, the natural happiness hormone. Vitamin D therefore acts as a vitality and tonicity booster, essential for immunity and indispensable for bone health.