Vitamin D

Vitamin D has long been known as "the sunshine vitamin" because the body can make it when the skin is exposed to sunlight. Actually, what we know as vitamin D really isn't a vitamin at all - it's a steroid hormone. Long ago it was misclassified as a fat-soluble vitamin and the name just stuck. It does have some of the same characteristics of a vitamin; namely, that people who are not exposed to sunlight need to get vitamin D from food or supplements just as they do for other vitamins. To make matters even more confusing, vitamin D is actually a general term for the many forms of the vitamin. The two major forms are vitamin D2, and vitamin D3, which were discovered in the 1930s.

Vitamin D2 is the plant form of the vitamin - the form found in some foods and used most often in supplements. Vitamin D3 is the form that's produced when the skin is exposed to sunshine. Some vitamin D3 is stored in the liver and kidneys, some goes to the bones, and the rest goes to the intestines to aid in calcium absorption from food.

Vitamin D can be found in foods such as salmon, milk, sardines, egg yolks, cheddar cheese, and butter.