Another layer to the vitamin D puzzle is understanding which form is best to take. In total, there are four different types of vitamin D. Yikes! No wonder it’s confusing! I’ll run through each one to clear up any befuddlement, then I’ll give you my opinion on which is best as a supplement.
There are 2 forms of Vitamin D that exist outside the body:
Vitamin D2 (ergocalciferol) – this type is only made in plants, and is not synthesized by the human body.
Vitamin D3 (cholecalciferol) – this type is made in animals, including us. We can ingest it in animal products, and we can make it when our skin is exposed to sunlight.
Here in the Northwest, it’s difficult to get enough exposure to sunlight. And even when we do, sometimes the UV rays from the sun are not strong enough to stimulate vitamin D production. The use of sunscreen also interferes with your body’s ability to manufacture the sunshine vitamin. Rather than slathering on the sunscreen before you go outdoors, spend about 15 minutes in the sun sans the screen so your body has the chance to produce vitamin D.
Back to types of vitamin D! We’ve covered the forms that exist outside (and at the very surface) of your body. Let’s take a look at what happens inside.
After cholecalciferol (D3) is produced, it enters the bloodstream and is transported to the liver. Here it is transformed into calcidiol, or 25(OH) vitamin D. Some is stored in the liver for future use, and some is circulated in the blood stream (this is the form that is checked on blood tests).
The final processing step for vitamin D occurs in the kidneys. Calcidiol is converted into calcitriol, or 1,25(OH) vitamin D. Calcitriol is a hormone, and represents the biologically active form of vitamin D. Its main purpose is to regulate calcium metabolism, though it also has much wider reaching effects in the body.
So which one is which when it comes to supplements?? As calcidiol and calcitriol are only produced in the body, they are not available in supplement form. Ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3) are available as supplements.
Vitamin D3 has been shown to be a more effective supplement than vitamin D2; it has a greater ability to raise blood levels of 25(OH) vitamin D (calcidiol) than vitamin D2. Unfortunately, the majority of prescriptions written in the US are for vitamin D2. However, most over the counter vitamin D and the vitamin D available in naturopathic offices is vitamin D3.
So next time you are picking up vitamin D, make sure it’s cholecalciferol, or D3. Your body will integrate it more readily, you’ll feel better faster, and your wallet will be happier!
Just as a reminder, before you start supplementing, make sure you get your levels checked, and talk to your naturopath about dosage.