Vitamin D Nutritional Status and Infectious Diseases

Hypovitaminosis D is highly prevalent worldwide [1]. Vitamin D importance is well known in bone diseases, but its role in infectious diseases has been recognised recently [2]. The main source of vitamin D is endogenous production in the skin under the influence of sun light. In the liver all vitamin D is hydroxylated to 25 hydroxyvitamin D (25OHD), which is the major circulating form of vitamin D, so serum levels of 25OHD are considered the best marker of nutritional vitamin D status. Under the control of feedback mechanisms 25OHD is hydroxylated in the kidney to the circulating hormone 1,25 (OH)2 D (calcitriol). Circulating calcitriol regulates calcium metabolism (“classical endocrine pathway of vitamin D”).