What is Vitamin D?

Vitamin D

Milk, which is fortified with vitamin D
Milk is fortified with vitamin D. CaseyHillPhoto/Getty Images

Definition: Vitamin D is an important nutrient and hormone that is found naturally in only a few foods (oily fish, cod liver oil and egg yolks) but is also made naturally in the skin with sunlight exposure. Many foods are also fortified with vitamin D, including breakfast cereals, milk and other dairy products. Vitamin D serves many important functions, include bone health and immune system health.

Deficiency of vitamin D can lead to an increase in asthma and allergies, as well as various bone diseases.

Learn more about the role of vitamin D in preventing asthma and allergies.

Continue Reading