Vitamin D3, also known as cholecalciferol, is the natural form of vitamin D for humans. Vitamin D3 is produced in the skin with sunlight exposure. Vitamin D2, known as ergocalciferol, is a compound produced by irradiating yeast with ultraviolet light.
A substantial body of research documents that vitamin D3 is the preferable form and researchers clearly recommend its use. Vitamin D3 has been found to be at least three times as potent as vitamin D2, and is more stable, safe, and useful in the body.
The less desirable vitamin D2 has been generally used in prescription vitamin preparations and in food fortification, while the nutritional and health food industries generally use the superior, natural vitamin D form, D3. Dr. John Cannell, vitamin D advocate and founder of the nonprofit Vitamin D Council, speaks of vitamin D3 in the following manner:
“If you take ergocalciferol, or “vegetarian” vitamin D, be warned. Ergocalciferol is not vitamin D, but a vitamin D-like patent drug whose patent has expired. It does not normally occur in the human body and is probably a weak agonist at the receptor site, meaning it may actually partially block vitamin D actions. Ergocalciferol is the villain in most of the reported cases of toxicity in the world’s literature. All bets are off in terms of measuring blood levels if you take ergocalciferol. Some of the labs can pick it up, and some can’t. Don’t take ergocalciferol; it is not vitamin D.” For more details, see Dr. Alan Gaby’s summary of the research comparing vitamin D2 and D3.
Interview with Dr. Cannell in the Townsend Letter for Doctors and Patients, November 2006, page 96.
Gaby AR. Vitamin D3 more potent than vitamin D2. Townsend Letter for Doctors and Patients, October 2005.