VDR and vitamin D deficiency: Given the widespread distribution of vitamin D receptors, which extend to the colon, osteoblasts, activated T and B lymphocytes and mononuclear cells, beta islet cells, brain, heart, skin, gonads, prostate, and breasts, it is anticipated that vitamin D deficiency will manifest in various extra-skeletal effects [26,27,28], such as an increased risk to the development of cardiovascular conditions, malignancies, immune system disorders, infections, chronic respiratory illnesses, and cognitive impairments [26,27,28,29,30,31].