Vitamin D1 vs D2 vs D3: What's the difference between them?

The term "Vitamin D" now refers to several different forms. The two forms important in humans are: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Vitamin D2 is a synthetic form (man made) and Vitamin D3 is the internal form that we make.

German researcher Adolf Windaus first discovered 3 forms of vitamin D, which he called D1, D2, and D3. It was later learned that the vitamin D1 was a mixture of compounds rather than a pure vitamin D product, so the term D1 is no longer used.

Read Next → The Vitamin D Guide