Vitamin D is an essential nutrient you need to maintain ideal health. You naturally create vitamin D when you are exposed to sunlight but can also get it through your diet or with dietary supplements. Vitamin D is an organic compound, and whether synthesized or found in nature, it is made up of the same elemental components.
Vitamin D Varieties
Vitamin D is a naturally occurring chemical compound, also known as calcitriol. The term "vitamin D" itself can refer to several types of related steroid molecules, such as vitamin D-3, or cholecalciferol, and vitamin D-2, or ergosterol. These varieties come from different sources. For example, plants naturally synthesize ergosterol, while animals produce cholecalciferol by absorbing sunlight through their skin.
Vitamin D is a hydrocarbon, meaning it is made up of a combination of the elements hydrogen, carbon and oxygen. The chemical structure of the varieties of vitamin D differ, but all forms are composed of only these three elements.
When your body creates vitamin D from exposure to sunlight, the form it creates is inactive, and the body must convert it to an active form. The body performs two separate transformative processes, known as hydroxylations, to convert the cholecalciferol form of vitamin D to a usable form. The liver performs the first transformation, taking the synthesized cholecalciferol and transforming it to 25-hydroxyvitamin D, or calcidiol. The kidneys then take this substance and transform it to 1,25-dihydroxyvitamin D, or calcitriol.
Vitamin D is only present naturally in a limited number of foods, and manufacturers add it to some foods, such as breakfast cereals and milk, during the production process. The nonfortified foods that have the highest amount of vitamin D include cod liver oil; different types of fish such as salmon, tuna and mackerel; and eggs.