Vitamin D, commonly known as the sunshine vitamin; is one of the most important vitamins in the human body. The vitamin is a unique one since it is produced by the exposure of the skin to sunlight. Those who are allergic to lactic products such as milk, follow a purely vegan diet, and have low exposure to the sun are particularly at risk of getting vitamin D deficiency. The vitamin is found in large quantities in fish, liver oils, egg yolk, milk and other food products. The main function of vitamin D is to extract calcium from food sources and make bones stronger and less brittle.