Vitamin D is the only vitamin that does not come from the foods eaten. Instead, vitamin D is actually obtained from sunlight on the skin. Much has been written in the media about the dangers of excessive sun exposure, but sun exposure is essential for the skin to get the recommended daily intake of vitamin D. In fact, the amount of time a person should spend in the sun to obtain a sufficient dose of vitamin D is extremely low and only a few minutes a day will suffice and will not have any negative effects from the amount of ultraviolet light received. The most important function of vitamin D is to help control the amount of calcium absorbed from food. Most calcium is used to build strong teeth and bones, but it’s also needed to send messages along nerves and to help muscles, such as the muscles of the heart, contract.It is vitamin D that ensures that there is always enough calcium in the blood to perform these tasks. Other functions that require vitamin D affect the immune system and it is also thought to be a contributing factor in reducing the risk of cancer and, in particular, colon cancer. The variant of vitamin D that forms under the skin is known as vitamin D3 or cholecalciferol. This vitamin D is created when ultraviolet rays from the sun react with a type of cholesterol that is naturally present under the skin. D3 is converted into a more active form of vitamin D in the liver and is then diverted to where it is needed most. Some vitamin D stays in the liver and kidneys to help reabsorb calcium from the blood.The rest of the vitamin D is dispersed in the bones to help them retain calcium and in the intestines to facilitate the absorption of calcium from food. Although most vitamin D is formed by exposure of the skin to sunlight, some foods naturally contain it. This form of vitamin D is known as vitamin D2 or ergocalciferol. used in the same way as other vitamin Ds and is the type used to create most vitamin D supplements.