Food, pills, liquid
Recommended daily allowance (in mcg):
A fat-soluble vitamin that is made by the skin when exposed to sunlight, vitamin D plays an important role in many biological functions. There are two basic forms of the vitamin: cholecalciferol (D3), which comes from sun exposure, and ergocalciferol (D2), which comes from plants. Whether received through sun exposure or by eating foods rich in the vitamin, the body must perform a number of conversions on vitamin D in order for it to be transformed into a usable form. People who live in northern climates (due to lack of sufficient sunlight) and the elderly are particularly prone to deficiency.
Rickets, a disease where the bones are soft and fragile, was a common problem in children in the days before milk was fortified with Vitamin D. This vitamin works in cooperation with calcium to strengthen bones and is important for the health of the entire musculoskeletal system. In addition, it boosts the immune system, helps regulate blood sugar and increases metabolism of calcium and phosphorus. It may also have a protective effect against cancer and reduce the progression of Alzheimer's disease and senile dementia.
Vitamin D deficiency symptoms include the following: Bone pain, frequent bone fractures, muscle aches, weakness, depression, and frequent colds.
Salmon, mackerel, sardines, herring, cod liver oil, fortified milk and cereal, and eggs.
It is not possible to get too much vitamin D from food or sunlight, however, those who take very high does in supplement form may experience side effects that include weakness, fatigue, headache, loss of appetite, dry mouth, metallic taste, nausea and vomiting. Some medications may be negatively affected by Vitamin D supplements, so first check with your doctor.