Symptoms of a vitamin D deficiency include impaired cognitive function, muscle weakness and bone pain. Children who are deficient in vitamin D may develop severe asthma, and adults suffer from an increased risk of cardiovascular disease.
Vitamin D plays an important role in healthy bone development. Specifically, it allows the body to use calcium to build healthy bones. If a child does not get enough vitamin D when he is growing, a condition known as rickets, in which the bones become soft, weak and often deformed.
Vitamin D is produced when the body is exposed to sunlight, and it is also in foods including fish and egg yolks. There are several possible causes of vitamin D deficiency, one of which is following a vegan diet that eliminates sources of vitamin D like cheese and fortified milk.
Another cause of vitamin D deficiency is limited exposure to sunlight; those who live at northern latitudes, wear long robes and head coverings, or are home-bound may not receive enough sunlight. Those with dark skin may also become deficient in vitamin D since their skin pigments reduce the body's ability to make the vitamin. Vitamin D deficiency is correctable with supplements and increased sun exposure.