Background Vitamin D is one of the major vitamin and very essential for maintenance of normal growth and development of strong bones. It is often referred to as the "sunshine vitamin" because it can be synthesized in the body from the ultraviolet rays provided by the sun. Vitamin D is known to have essential roles in the human body. However, the case of vitamin deficiency is reported to increase in many adult worldwide, especially in Saudi Arabia. Vitamin D deficiency is associated with numerous chronic diseases including cancer, heart disease and diabetes type 1 and 2. It is currently estimated that one billion people suffer from vitamin D deficiency worldwide. Sunlight is the main and natural source of vitamin D and most foods contain very little amount of it. The main action of vitamin D is to help calcium and phosphorus in our diet to be absorbed from the gut.