Previously, known actions of vitamin D were confined to skeletal health, but accumulating
evidence has consistently suggested that vitamin D has pleomorphic roles in
overall human physiology. Hence, no other micronutrient deficiency in the modern
times has gained as much global attention as vitamin D deficiency. In this chapter, the
author reinforces what is already known in vitamin D and highlights several important
findings in vitamin D research, with a special focus on one of the most vitamin Ddeficient
regions in the world, the Middle East, and Saudi Arabia, in particular.