There are two common forms of vitamin D available: D2 or ergocalciferol and D3 or cholecalciferol. D2 is the form found in mushrooms, cocoa and chocolate (from fungal contamination) and a few other places, while D3 is the human form.
There’s a basic rule in health: Humans should take human hormones, when needed. Break this rule and weird things happen. The last time I checked the reader list for the Wheat Belly Blog, all readers were human, no sign of button, Portabella, or
If you are a human male with low testosterone, should you be prescribed frog or squirrel testosterone? I don’t think so. (Let’s put aside the fact that testosterone levels can be raised naturally.) If you are a human female, should you take horse estrogens as contained in Premarin? Many women did for many years until it became clear that doing so increased potential for endometrial cancer, breast cancer, fatal heart disease, and accelerated dementia—bad things happen when humans take non-human hormones. (Why was Premarin the #1 most prescribed drug in the world for many years, not human estrogens? Because the horse estrogens in Premarin were patent-protectable, not because they were superior to human hormones.)
How are D2/ergocalciferol and D3/cholecalciferol different?
- D3 is substantially more effective in raising blood levels of 25-OH vitamin D. It requires about 250% more D2 to achieve the same blood level as D3.
- D2 does not bind to the vitamin D binding protein with the same strength as D3, meaning it exerts its effects for less time and is cleared from the blood faster.
- While D3 has been shown to have effects such as reduced falls and bone fractures, D2 may not.
- D3 has been shown to increase strength, while D2 does not
To illustrate the differences in behavior between the two forms, a single 50,000 unit dose of either D2 or D2 was administered to healthy volunteers, then 25-OH vitamin D blood levels followed over 28 days:
(From Armas 2004.)
You can see that D3 yields a much higher 25-OH blood level (nmol/L) and is sustained for much longer than D2.
Vitamin D authority, Dr. Reinhold Vieth of the University of Toronto, has declared that “Vitamin D2 should no longer be considered equivalent to vitamin D3 and that vitamin D2, or ergocalciferol, should not be regarded as a nutrient suitable for supplementation or fortification.” In other words, nobody should be taking D2. Ergocalciferol may have served its purpose, being included in dairy products over the years to prevent infantile rickets, but we now know that there are better ways to manage your vitamin D. Note that the majority of people taking prescription vitamin D are taking D2/ergocalciferol—if you do, it’s time to make a change in vitamin D form, as well as your doctor.
Getting vitamin D right takes on heightened importance during this viral pandemic, as vitamin plays a critical role in T-cell immunity against viruses. Vitamin D is so effective that most of us on the Wheat Belly lifestyle almost never get sick with the flu or viral illnesses. We don’t yet know just how much better immunity becomes against coronavirus with vitamin D restoration, but there is no downside, only potential upside. For this reason, we aim for an ideal 25-OH vitamin D blood level of 60-70 ng/ml.