Abstract
Vitamin D(3) deficiency and insufficiency are becoming a common global issue for us, especially in the most industrially developed countries. The only acknowledged activity of vitamin D(3) in vertebrates is to promote the absorption of calcium and, therefore, allow for the mineralization of bones. Accordingly, its deficiency is associated with diseases such as rickets. Other numerous vital functions associated with vitamin D(3) are yet to be considered, and the function of vitamin D(2) in plants is unknown. Thus, 100 years after its discovery, the importance of vitamin D still seems to be unacknowledged (except for rickets), with little attention given to its decrease throughout the world. In this review, I suggest that vitamin D deficiency and insufficiency may be linked to the westernized lifestyle in more developed countries. Furthermore, I suggest that, rather than the calcemic activity, the main function of vitamin D is, in general, that of strengthening living organisms. I conclude with the hypothesis that vitamin D deficiency may represent a marker for a greater risk of chronic inflammatory diseases and a shorter life expectancy.