Vitaminworkshop.com - New Vitamin D Basics

This is the conclusion from a most informative analysis by Anthony W. Norman in AJCN Vol 88 No 2 pages 4915-4995.

"Conclusions

Recent research has shown that vitamin D₃'s biological sphere of influence is much broader than researchers originally thought, as shown by the tissue distribution of the VDR, from mediating only calcium homeostasis (intestine, bone, kidney, and parathyroid) to functioning as a pluripotent hormone in 5 physiologic arenas in which researchers have clearly identified additional biological actions of 1α,25(OH)₂D₃ through the VDR. These physiologic arenas are the adaptive immune system, the innate immune system, insulin secretion by the pancreatic β cell, multifactorial heart functioning and blood pressure regulation, and brain and fetal development.
) Researchers have also expanded the parent vitamin D₃'s nutritional sphere of influence from a focus on bone health to include 5 additional physiologic systems.
) The nutritional guidelines for vitamin D₃ intake must be carefully reevaluated to determine the adequate intake (balancing sunlight exposure with dietary intake) to achieve good health by involving all 36 target organs rather than just the first 4 target organs (intestine, kidney, bone, and parathyroid gland) that are considered for calcium homeostasis.

Corollary-  Given that vitamin D₂ is significantly less biologically active (33%-50%) over time in humans than is vitamin D₃ (7), its biological use as a dietary supplement in the United States should be discontinued and its use in a high-dose form [eg, 500 000 IU/mL of ergocalciferol (vitamin D₂)] in clinical studies (73, 74) and as described in the Physicians Desk Reference (75) should be replaced by a new formulation of (lower) high-dose vitamin D₃."

Vitamin D on Immunity

This issue is very critical to a number of diseases. Vitamin D participates in the production of LL-37. This element has a role to play against pathogens attacking the body. This reference has a lot of facts and studies on vitamin D actions. Copied next from the preceding reference is an interesting take on vitamin D and colon health through the vitamin D receptor, VDR.

"The accumulating evidence suggests that in the intestinal tract, the byproducts of gut microbes could be important for communicating with the epithelial cells, thus modulating the expression of the cathelicidin gene. This may be important for establishing a moustached barrier to prevent contact of microbes and pathogens with the intestinal epithelium. This is nicely demonstrated by the ability of short-chain fatty acids such as sodium butyrate that are produced by fermentation of fiber by microbes in the colon to induce expression of the cathelicidin [92]. The vitamin D pathway has been implicated in this induction [117]. The production of secondary bile acids by microbes may modulate cathelicidin expression in the colon via the VDR. One could speculate that the selective force for placing the cathelicidin gene under the regulation of the VDR was so its expression could be regulated by both vitamin D and xenobiotic factors (Figure 4).

A recent study indicates that the VDR may act as a receptor for additional nutritional ligands, including curcumin and polyunsaturated fats such as α-linolenic acid (ALA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and arachidonic acid (AA) [118]. The in vivo relevance of these findings remains to be elucidated, but it is intriguing to consider that numerous nutritional compounds may modulate the expression of VDR target genes such as antimicrobial peptides."

LL-37 is significant to vitamin D levels and functions for the immune system. Here is a reference with greater insights. Copied next are the abstracts on Results and Conclusions of last reference.

Results

Critically ill subjects had significantly lower plasma 25(OH)D concentrations (storage vitamin D form) compared to healthy controls. Mean plasma LL-37 levels were significantly lower in critically ill subjects compared to healthy controls. Vitamin D binding protein (DBP) levels in plasma were significantly lower in critically ill subjects with sepsis compared to critically ill subjects without sepsis. There was a significant positive association between circulating 25(OH)D and LL-37 levels.

Conclusion

This study demonstrates an association between critical illness and lower 25(OH)D and DBP levels in critically ill patients as compared to healthy controls. It also establishes a positive association between vitamin D status and plasma LL-37, which suggests that systemic LL-37 levels may be regulated by vitamin D status. Optimal vitamin D status may be important for innate immunity especially in the setting of sepsis. Further invention studies to examine this association are warranted.