Cholecalciferol is a form of vitamin D, also known as vitamin D3. Its structure is similar to steroids, such as testosterone, cholesterol, and cortisol (though vitamin D3 itself is a steroid).
Cholecalciferol is industrially produced to supplement vitamins and to strengthen foods by irradiating 7-dehydrocholesterol extracted from lanolin found in sheep wool with ultraviolet light.
In foods that do not require animal products, another compound is ergocalciferol (also known as vitamin D2) derived from the fungal sterol ergosterol.
Here are the simplified steps for vitamin D3 production:
Depending on the breed, healthy sheep will produce 2 to 30 pounds of wool per year.
Wool is cut from mature live sheep.
Crude lanolin is extracted from wool through a washing process, in which the wool is washed with hot water using a detergent.
Crude lanolin undergoes a saponification process; this separates the fat component removed by centrifugation from the "unsaponifiable" component called "lanolin alcohol". These are subjected to further saponification and separation steps to increase purity.
Crude cholesterol is extracted from lanolin alcohol using solvent washing and / or column chromatography.
The crude cholesterol is subjected to a series of further solvent extractions, washing and drying until it is extremely pure and crystallized.
The purified cholesterol is then used to make 7-dehydrocholesterol through a four-step chemical process, also known as the "vitamin D3 precursor"
Next, pre-vitamin D3 is irradiated to produce Vitamin D3 (Cholecalciferol); this is the same reaction that human skin uses to make vitamins from sunlight. Some unwanted isomers are formed during irradiation. They are removed by various techniques, and the remaining resin melts at about room temperature, typically with a potency of 25,000,000 to 30,000,000 international units per gram. Finally, the pure crystals of vitamin D3 are used to make stable product forms that can be used to make dietary supplements and other end uses, such as food and beverages.