Vitamin D

I have encountered many questions regarding this Vitamin, especially in the winter and living in Canada.

There are 3 types: D2, D3, and D5. Of the 3, D3 (cholecalciferol) is considered the natural form. D3 is made in the skin as a response to exposure of the sun's UV rays.
It is fat-soluble, which means that you CAN get too much of it, and the liver will have trouble getting rid of excess. D requires conversion by the liver and then the kidneys.
It has the properties of a vitamin and a hormone and is necessary for the absorption of Calcium and Phosphorus. It is necessary for growth and development of bones and teeth. It protects from muscle weakness, and thereby is involved with the regulation of the heartbeat. Also, it helps in protection of breast and colon cancer, is needed for thyroid function and normal blood clotting.
Vitamin D enhances immunity - important in the winter months when sunlight is limited, and flu season takes place.
Darker skinned people whose pigment blocks sunlight, cannot produce sufficient amounts of D.

Recommended intake: 1,000 I.U.'s daily

Hope this helps.