I recently heard some new (to me) information on Vitamin D. Wikipedia says, "Vitamin D is a group of fat-soluble prohormones." It's not really a vitamin like the other main ones; A, B, C, etc.
The main conclusion was most of us are D deficient. It's in very few of our foods and we need some sunlight for the chemical reactions. Part of the problem is most likely related to people being inside and out of the sun more these days.
What do you know about D and do you know the level of it in your body? Eat right and stay healthy.
"Vitamin" D is not vitamin because strictly speaking, a vitamin is a chemical substance that cannot be produced by the body. However the body can indeed produce "vitamin" D from nutrients and sunshine, besides taking it directly from diet. Other vitamins (A, B, C etc.) cannot be produced in human body.
Vitamin D is a secosteroid of nutritional origin but can also be generated in the skin by ultraviolet light. After two hydroxylations 1,25-(OH)2 vitamin D avidly binds and activates the vitamin D receptor (VDR), a nuclear transcription factor, hereby regulating a large number of genes. The generation of VDR deficient mice has expanded the knowledge on vitamin D from a calcium-regulating hormone to a humoral factor with extensive actions. The effects of the vitamin D system on calcium and bone homeostasis are largely mediated by promoting active intestinal calcium transport via the induction of the epithelial calcium channel TRPV6. Although VDR is redundant in bone, it may regulate the differentiation and function of several bone cells. In skin, VDR expression in keratinocytes is essential in a ligand-independent manner for the maintenance of the normal hair cycle. Therefore, VDR but not vitamin D deficiency results in alopecia. Moreover, 1,25-(OH)2 vitamin D impairs the proliferation not only of keratinocytes but also of many cell types by regulating the expression of cell cycle genes, leading to a G1 cell cycle arrest. In addition, VDR inactivation in mice results in high renin hypertension, cardiac hypertrophy and thrombogenesis. Finally, a dual effect of vitamin D was observed in the immune system where it stimulates the innate immune system while tapering down excessive activation of the acquired immune system. Taken together, the vitamin D endocrine system not only regulates calcium homeostasis but affects several systems mainly by altering gene expression but also by ligand-independent actions.
