Vitamin D is best known for its role in the development and maintenance of healthy teeth, bones, and cartilage in children and adults. Vitamin D helps the body keep bones and teeth strong by increasing absorption of calcium and phosphorus from the small intestine.

There are two forms of Vitamin D: ergocalciferol, which is found in such foods as fortified milk, herring, mackerel, tuna, salmon, sardines, eggs, fortified cereals and baked goods; and cholecalciferol, which is manufactured when the body is exposed to sun.

Vitamin D is fat-soluble. This means that excess amounts of it are stored in the body tissues. Long-term high doses may be deposited in the soft tissues, irreversibly damage the kidneys and cardiovascular system. Like other fatsoluble vitamins, vitamin D can be toxic. Symptoms of too much vitamin D include nausea, weakness, constipation, irregular heartbeat, weight loss, seizures, and irritability.

Vitamin D is one of those vitamins for which a deficiency can cause severe effects. Children that do not get enough vitamin D in their diets are at increased risk of developing rickets, a disease that causes malformations of bones and teeth in children. Adults with low levels of vitamin D are more likely to develop osteomalacia (similar to rickets) and to suffer from osteoporosis, a bone-weakening disease.Vitamin D2 /Ergocalciferol is one major form of vitamin D which can prevent and treat osteoporosis and rickets.It also has a part in cancer prevention,at least for colon cancer.