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Vitamin D2 vs. D3: what’s the difference?

Vitamin D plays a crucial role in helping people with MS maintain their health - when choosing a supplement, vitamin D3 (cholecalciferol) is the preferred option.

Vitamin D comes in two main forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Both help the body maintain healthy bones and support the immune system, but they come from different sources and work slightly differently in the body.

Where are they found?

  • Vitamin D2: Found in plant-based sources like mushrooms (especially those exposed to UV light) and fortified foods (such as cereals and plant-based milk).
  • Vitamin D3: Found in animal-based sources like fatty fish (salmon, mackerel), fish liver oils, egg yolks, and dairy products. It is also produced naturally in the skin when exposed to sunlight (UVB rays).

What is the difference?

Vitamin D3 is more bioavailable than vitamin D2, meaning it is absorbed and used more efficiently by the body. Bioavailability refers to how much of a substance actually gets into your bloodstream and is available for your body to use. A nutrient with higher bioavailability is absorbed more effectively and stays in the body longer, making it more beneficial.

A recent study compared how well vitamin D2 and vitamin D3 increase vitamin D levels in the blood. While both forms are available as supplements, vitamin D3 was found to be 40% more effective than D2 at raising overall vitamin D levels.

This is because:

Vitamin D3 lasts longer in the body

It remains in circulation for a longer time, helping to maintain stable vitamin D levels.

D3 is more easily converted into the active form

The body converts both D2 and D3 into 25-hydroxyvitamin D (25(OH)D), the form measured in blood tests. However, vitamin D3 is converted more efficiently, leading to higher and longer-lasting vitamin D levels.

D3 binds better to vitamin D receptors

This means it has a stronger effect on key processes like immune system support and calcium absorption.

Which one is better for MS?

Vitamin D3 is the better choice for people with MS so when choosing supplements check they say vitamin D3 (cholecalciferol) as well as the units they contain. For more information on how much vitamin D to supplement with head to our main page here.

References

Comparison of the Effect of Daily Vitamin D2 and Vitamin D3 Supplementation. This study compared the effectiveness of Vitamin D2 and D3.  

Further Reading