Vitamin D is a fat-soluble vitamin that plays a role in many
important body functions. It is best known for working with
calcium in your body to help build and maintain strong bones.
Vitamin D is also involved in regulating the immune system and
cells, where it may help prevent cancer. Your body stores
vitamin D and can make it when your skin is exposed to sunlight.
Vitamin D is also found in some foods, mostly ones like milk
that have been fortified with vitamin D. There are two forms of
vitamin D: ergocalciferol (vitamin D2) and cholecalciferol
(vitamin D3). Some research suggests that cholecalciferol is
better at raising levels of vitamin D in the blood. In children,
a vitamin D deficiency can cause rickets, a disease that results
in soft, weak bones. In adults, many people may not be getting
enough vitamin D, especially those who live in northern areas
(like the northern half of the U.S.) and the elderly. People
with dark skin do not absorb sunlight as easily as those with
light skin, so their risk of low