What does vitamin D do?
Vitamin D helps the body absorb calcium and phosphorus, which are needed for strong bones and teeth. It also supports muscles, nerves and the immune system.
Our skin makes vitamin D when it is exposed to ultraviolet B rays from sunlight. That is why it is often called the sunshine vitamin. People living far from the equator, people with darker skin and those who spend most of their time indoors may not make enough, especially in winter.
Few foods naturally contain much vitamin D. Good sources include oily fish such as salmon, sardines and mackerel, egg yolks and some mushrooms. Many countries add vitamin D to milk, cereals and other foods. Some health authorities recommend supplements during autumn and winter.
Too little or too much
A lack of vitamin D can cause rickets in children, which leads to soft, bent bones, and osteomalacia in adults, which causes bone pain and weakness. However, taking too much from supplements can cause calcium to build up in the blood, which can be harmful. Sunlight alone does not cause vitamin D overdose.
Did You Know?
Vitamin D is technically a hormone as well as a vitamin, because the body can make it and it acts as a chemical messenger.
This answer is general information, not medical advice. For a personal health question, talk to a doctor.