information about vitamin D

Cholecalciferol (also known as toxiferol) is a form of vitamin D, also called vitamin D3.
It is structurally similar to steroids such as testosterone, cholesterol, and cortisol (though vitamin D3 itself is a secosteroid).

Cholecalciferol is produced industrially for use in vitamin supplements and to fortify foods by the ultraviolet irradiation of 7-dehydrocholesterol extracted from lanolin found in sheep's wool. Paraphrasing a more detailed explanation,cholesterol is extracted from wool grease and wool wax alcohols obtained from the cleaning of wool after shearing. The cholesterol undergoes a four step process to make 7-dehydrocholesterol, the same compound that is stored in the skin of animals. The 7-dehydrocholesterol is then irradiated with ultra violet light. Some unwanted isomers are formed during irradiation. These are removed by various techniques, leaving a resin which melts at about room temperature and usually has a potency of 25,000,000 to 30,000,000 International Units per gram. Cholecalciferol is also produced industrially for use in vitamin supplements from lichens, which is suitable for vegetarians and vegans.
An alternative compound is ergocalciferol (also known as vitamin D2) derived from the fungal sterol ergosterol.