Vitamin D supplements: Magic pill or overkill?

Abstract

Vitamin D is a multifunctional micronutrient that exerts hormonal effects on many organs of the body. 1,25 dihydroxyvitamin D is the active metabolite of vitamin D, formed by dual hydroxylation in the liver and kidney (Figure 1).1 Circulating 1,25 dihydroxyvitamin D exerts biological functions, mainly through interaction with vitamin D receptors (VDRs), and can increase the intestinal absorption of mineral ions such as calcium and phosphate; it can also suppress the biosynthesis of parathyroid hormone. High serum levels of 1,25 dihydroxyvitamin D are believed to increase osteoclastic bone resorption, which mobilizes calcium and phosphate from bone. Of relevance, vitamin D is a strong inducer of fibroblast growth factor 23 (FGF23) and klotho, two important homeostatic regulators of calcium and phosphate metabolism. [2][3][4] An association between hypovitaminosis D and ageassociated disorders, including osteoporosis, cancer, diabetes, autoimmune disorders, hypertension, atherosclerosis, and muscle weakness is reported; a similar association is also noted with neurological disorders