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The difference between vitamin D2 & D3 - which is better?

Chemical diagram of vitamin D2 and D3
Published on: 
01/09/2021 - 09:16

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A brief overview on vitamin D group

Vitamin D is a fat-soluble vitamin and an essential nutrient for various bodily functions. It is critical to muscle and bone health, as well as in maintaining a strong respiratory, cardiovascular, immune, brain and nervous system. It also aids in regulating insulin levels, managing diabetes, and influencing gene expression in cancer development. For this reason it is important to know if you are deficient in vitamin D because it is so critical.

When exposed to sunlight, our skin produces vitamin D. However, most of us avoid sun exposure due to the risk of developing skin cancer, so we end up being vitamin D deficient.

How do you get vitamin D and in what form?

Although there are certain milk and dairy products and orange juice fortified with vitamin D, as well as oily fish, eggs, meat and mushrooms that contain it in small amounts, we usually do not get enough of the minimum 5 micrograms (200 IU) recommended in Australia for children, adolescents and adults aged 19 to 50 years.

Because of this, you may need to take a vitamin D supplement. The two main forms of vitamin D available for supplementation are D2 (ergocalciferol) and D3 (cholecalciferol).

In this article, we’ll talk about the differences between the two, which of them is the superior form of vitamin D for supplementation and why.

Illustration of different vitamin D sources

Where are vitamin D2 and D3 each derived from?

While supplementing with either vitamin D2 and D3 can help you meet your vitamin D requirements, these two types of vitamin D come from different sources.

Vitamin D2 can be found in plant sources (e.g., wild mushrooms), yeast and fortified orange juice, milk and cereal products. It is relatively cheaper to make, which is why it’s the kind of vitamin D used for fortifying food products.

Meanwhile, our skin can produce vitamin D in the form of D3 when it is exposed to sunlight – which is why it’s called the ‘sunshine vitamin’. It’s available in large amounts in some animal sources like cod liver oil and fatty fish such as salmon and trout. It's present in smaller amounts in eggs, sardines, tuna, cheese and beef liver.

Differences in how D2 and D3 are supplemented

Although vitamin D2 and D3 are both available as supplements, they differ in terms of strength, potency and absorption. More importantly, they are indicated for different reasons. However, vitamin D2 and D3 both come in 50,000-unit capsules. The confusion begins when your doctor gives you a prescription for vitamin D without indicating which one they are referring to. It is then up to the pharmacist to verify which type you should be taking.

Before, it was assumed that vitamin D2 and D3 were similar, so it didn't matter which one was taken, but that is not the case anymore. Vitamin D2 has been found to be less potent than vitamin D3, and it also requires a prescription at 50,000 units when the latter does not. And while vitamin D2 is used to treat certain problems like rickets, familial hypophosphatemia (an electrolyte disorder) and hypoparathyroidism (decreased function of the parathyroid glands), vitamin D3 is recommended for use as a vitamin or dietary supplementation.

How they are metabolized by the liver into 25D

Vitamin D2 and D3 have similar roles in the body, although they have small differences in their molecular structures. The bloodstream absorbs either form effectively, but they are metabolized by the liver differently.

Vitamin D2 is metabolized into 25-hydroxyvitamin D2 by the liver and vitamin D3 into 25-hydroxyvitamin D3. Both 25D versions are referred to as calcifediol – which is the primary form of vitamin D circulating in the human body.

The level of 25D in your blood indicates whether you have enough or are deficient in vitamin D – which is why your physician or healthcare provider measures your levels of calcifediol to know your vitamin D status.

However, it has been observed that vitamin D2 produces lower amounts of calcifediol when compared to a similar amount of vitamin D3. In fact, some studies have shown that vitamin D3 can increase the level of calcifediol in the blood. A study involving 32 older women showed that one dose of vitamin D3 was almost twice as efficacious in bringing up calcifediol levels when compared with vitamin D2.

In another clinical trial that compared a 10-week regimen of individuals in demographically similar groups, the participants were dosed twice weekly with 50,000 IU of both vitamin D2 and D3. Here, the researchers found that vitamin D3 effectively produced higher levels of 25D or calcifediol than vitamin D2.

This is why it is recommended that you consider taking vitamin D3 in case you need to supplement with vitamin D. After all, it is the type of vitamin D that’s primarily intended for supplementation purposes.

The right kind of vitamin D

Taking vitamin D3 supplements is the better choice for vitamin D deficiency. However, before taking any supplement or medicine, please check with your physician or healthcare provider.