| Outcome | Mechanism |
| Autoimmune Diseases | Regulates adaptive immunity so that the body does not attack its own tissues |
| Bone health | Regulates calcium and phosphorus absorption and metabolism |
| Cancer | Reduces incidence by affecting cellular differentiation, proliferation, and apoptosis; reduces mortality by reducing angiogenesis around tumors and metastasis; many other mechanisms |
| Cardiovascular disease | Reduces incidence by affecting cellular differentiation, proliferation, and apoptosis; reduces mortality by reducing angiogenesis around tumors and metastasis; many other mechanisms |
| Infectious diseases | Induces production of antimicrobial peptides such as human cathelicidin; reduces risk of cytokine storm; Inhibits expression of proinflammatory cytokines through blocking the TNF-induced NF- B1 signaling pathway; and initiates expression of ISGs for antiviral defense program through activating the IFN- -induced Jak-STAT signaling pathway |
| Inflammation | Shifts production of cytokines from Th1 (proinflammatory) to Th2 (anti-inflammatory) |
| Insulin resistance | Maintains pancreatic-cell function; increases insulin sensitivity in insulin-responsive tissue; reduces serum concentrations of parathyroid hormone; regulates renin- angiotensin-aldosterone system; exerts positive effects on hepatic lipogenesis and gluconeogenesis; reduces formation of reactive oxygen species |
| Muscle health | Regulates oxygen consumption rate, maintains mitochondrial function, reduces risk of muscle atrophy |
| Pregnancy outcomes | Most effects mediated by calcitriol, whose concentrations increase during pregnancy. Calcitriol regulates calcium absorption from the GI tract. Calcitriol produced in the placenta acts as an autocrine/paracrine regulator of immunity at the fetal-maternal interface for acceptance of the fetal allograft; calcitriol regulates estradiol and progesterone secretion in the placenta; calcitriol downregulates FLT1 and vascular endothelial growth factor gene expression, thereby reducing risk of preeclampsia. Calcitriol regulates immune function through effects on cytokine production |
FLT1 – FMS-like tyrosine kinase 1;
GI – gastrointestinal;
IFN – interferon alpha;
ISGs – interferon-stimulated gene;
TH – T-helper cell;
TNF – tumor necrosis factor.