Should You Take Vitamin D2 or Vitamin D3?

vitamins sitting next to a cup of tea

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If you need to take vitamin D supplements, you may encounter two different types on the drugstore shelf: vitamin D2 and vitamin D3. While it may seem fair to assume that vitamin D3 is an improvement on vitamin D2, they are mainly differentiated by the fact the one is found in plants and the other is found in animals.

While both aid in the absorption of calcium and reduce your risk of bone loss (osteoporosis), there are subtle differences that may inform your choice of supplement.

Vitamin D2

Vitamin D2 is also known as ergocalciferol. It was first described in medical literature in 1936 and has been on the World Health Organization's List of Essential Medicines since it was first published in 1977.

The ergocalciferol found in vitamin D2 supplements is derived from certain mushrooms (portobello, shiitake, crimini) as well as alfalfa and a type of moss known as Cladina arbuscula. When these plants are exposed to an industrial ultraviolet lamp, the ergocalciferol content will increase to higher levels.

Ergocalciferol is inactive on its own. If taken as D2 supplement, it only becomes active if it undergoes two chemical reactions, one in the liver and the other in the kidneys.

Vitamin D3

Vitamin D3 is also known as cholecalciferol. It is the type created naturally in the human body when the skin is exposed to sunlight. As with ergocalciferol, it was first described in 1936 and is also on the WHO List of Essential Medicines.

The cholecalciferol in vitamin D3 supplement is a type of cholesterol known as 7-dehydrocholesterol (7-HDC) derived from lanolin in sheep's wool. 7-HDC is the exact compound found in the skin of animals and humans.

As with ergocalciferol, cholecalciferol in inactive by itself. It also needs to undergo specific chemical reactions in the liver and kidneys, although the enzymes used to make it active are different than those used for ergocalciferol.

Similarities and Differences

Whether you take vitamin D2 or vitamin D3, the supplement will be converted in the liver and kidneys into the active form of vitamin D known as calcitriol. In its active state, calcitriol will bind to a protein on cells known as a vitamin D receptor (VDR) as well as a third protein called retinoid X receptor

This cluster will then bind to the portion of DNA in your cells that regulates the absorption of calcium and phosphate in the body. Whether you take vitamin D2 or vitamin D3, the process will be the same.

The only difference is that vitamin D3 tends to bind more effectively than vitamin D2. What this means is that vitamin D3 supplements are more potent and require lower doses to achieve the same health benefits.

According to research published in the American Journal of Clinical Nutrition, vitamin D3 has a potency that is between 1.7 and 3 times greater than that of vitamin D2. The translates to several different things:

  • Vitamin D3 has a longer duration of effectiveness compared to vitamin D2.
  • In order to achieve equal potency and duration, vitamin D2 supplements need to be formulated up to ten times the international units (IUs) per dose that vitamin D3 supplements are for certain health conditions.

Choosing Wisely

Whether this makes one vitamin "better" than another is up for debate. Given that your body doesn't care whether it's taking more vitamin D2 or less vitamin D3—as long as it's within the recommended dose—either type could be perfectly fine if you're taking it for general health.

However, if you need it a specific health condition, the differences between the two can end up really mattering. To many nutrition experts, the two supplements are not bioequivalent.

If you have osteoporosis or other bone-weakening diseases (such as osteomalacia and osteopenia), it would be hard to say that vitamin D2 is "just as good" as vitamin D3.

At the same time, when prescribed at a 50,000-IU dose, vitamin D2 can be extremely effective in aiding in the treatment of rickets, hypoparathyroidism (decreased parathyroid function), and hypophosphatemia (low phosphate levels).

In the end, if you are taking vitamin D as a means to treat or prevent a disease, it is best to discuss the appropriate option with your doctor or health care provider.

A Word From Verywell

If you're at risk of osteoporosis and concerned about your vitamin D levels, the best thing to do is go to your doctor to have your blood levels checked. If they're low, you can take either form of vitamin D and, after a few weeks, have your blood checked again to see if the supplements are working.

In the meantime, try to bolster your diet with vitamin D-rich foods and spend ample time in the sun (with the appropriate sunblock, of course). Never exceed the recommended dose on supplements label unless your doctor tells you otherwise.​

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