A balanced diet will provide us with dietary vitamin D, however often times dietary sources of vitamin D are not consistent enough to support our daily needs. Research suggests that seasonal changes in the weather may also have an effect on the amount of vitamin D we are able to make. People living in areas were winters are cold and long may not be getting the vitamin D requirements they need.
Vitamin D is converted in the body to the active 1,25(OH)2 form. This conversion is regulated by parathyroid hormone (PTH) and low levels of calcium and phosphorus. Vitamin D is available in two different forms, increase 25(OH)D levels for a longer period of time when compared to vitamin D2.