Dear Eric

Vitamin D is endogenously produced after skin exposure to Ultraviolet B (UVB) light and can be consumed by fortified foods or supplements . Food sources of vitamin D are limited and include mostly animal-based foods such as seafood, eggs, milk and dairy products.The accepted adequate vitamin D serum levels are above 30 ng/ml. Supplements of Vitamin D3 (Cholecalciferol) which made from animal sources and Vitamin D2 (Ergocalciferol) which made from plant sources are available. Today even vitamin D3 made from plant sources are available (for example: Vitashine Vegan Vitamin D3 Supplements .see: http://vitashine-d3.com/ ). The vitamin D3 supplaments (made form animal sources) are more common presently. At doses lower than 1000 IU, vitamin D2 and D3 appear equally effective; however, at doses higher than 1000 IU/day, vitamin D3 appears to be significantly more effective at raising serum D concentrations . I hope that I understood what that you asked :)

Best regards,

Shiri

As mentioned by Shiri, most vitamin D supplements are from animal sources;

An interesting question is how do animals with fur get vitamin D3 (since the fur blocks sunlight). Have you seen animals licking their fur? They secrete oily (lipid soluable) provitamin D3 which covers their fur, then after UV irradiation, they lick it off! This is the secret to how we humans harvest animal vitamin D... Which animal fur oil do we have access to? Lanolin from sheep's wool. Australia has a lot of sheep and we are one of the world's largest producers of medicinal Vitamin D.

[Vit D3 can also come from fish (esp fish liver), but the lanolin story is nicer.]

[[Vit D2 from radiation of plant material (eg fungi) is not as natural or effective.]]

Dear Shiri,

Thank you for your answer. As you mentionned, supplements of Vitamin D3 are made from animal sources and Vitamin D2 are made from plant sources. And we are veryn interested in knowing more about these different sources, the production process and chain values.

Dear Ken,

Thank you very much for your anser which is clearly the kind of answers we are looking for (e.g. lanolin from sheep's wool and Australia being one of the world's largest producers of medicinal Vitamin D). 

If you have some references or sources to learn more about this, thank you for sharing them. But I agree with you, the lanolin story is a very nice story!!

Hey Eric,

you should finde some info here:

Hirsch, A. L. (2011). Industrial aspects of vitamin D. In Chapter 6 in Vitamin D: Two-Volume Set (pp. 73-93). Academic Press.

David

Dear David,

Thank you very much for your anser - and sorry for the very long delay! You provided a very good reference:

"Summary: The four major commercial products of vitamin D are vitamin D3 and D2, 25-hydroxyvitamin D3 and 1α-hydroxyvitamin D3. Vitamin D3 is manufactured from cholesterol which is isolated from wool grease. The cholesterol is converted chemically to 7-dehydrocholesterol which is irradiated with UV light to form pre-vitamin D3 and cisvitamin D3, the biologically active precursors to the vitamin D3 metabolites. The irradiation and heating processes are carefully controlled to avoid generating the many isomeric inactive forms of the vitamin from being generated. Vitamin D2 is obtained using similar irradiation techniques with ergosterol. Ergosterol is obtained from yeast fermentation. Most of the manufacturing of cholecalciferol and ergocalciferol is currently being done in China. Worldwide use is 97.3 metric tons. 25-Hydroxyvitamin D3 is predominately made from 25-hydroxy-7-dehydrocholesterol which is produced through a process involving fermentation of modified yeast. 1α-Hydroxyvitamin D3 is made through a chemical process starting with pure vitamin D3."