Supplements

Vitamin D2 vs. D3: The Key Difference—Plus Which Is Best for Supplementation

Written by Lauren Manaker, RDN, CLE
Medically Reviewed by Felicia Newell, M.S., RDN

Updated on October 23, 2024

The supplement aisle can be confusing—an endless wall of bottles to support every aspect of your mental and physical health. Luckily, your doctor just said to pick up some plain old vitamin D—that should be easy enough, right?

Not quite…

Not only are there tablets, gel caps, and tinctures in different dosages and ingredients, but there’s also the choice between vitamin D2 and D3. Your doctor didn’t specify which kind, so how do you choose?

In this article, we’ll explain the similarities and differences between D2 and D3, and then reveal which is best for supplementation.

Table Of Contents

Vitamin D2 vs. D3: A Side-by-Side Comparison

One of the main myths about vitamin D is that it’s just one nutrient. When in fact, it’s a family of two: vitamin D2 and vitamin D3.

At a glance, they seem similar…

  • They’re both fat-soluble. 
  • They’re processed by the kidneys and liver and converted into calcitriol (their active form).
  • And they play a part in regulating calcium and phosphorus metabolism, supporting bone health, and influencing immune function.

But their similarities stop there.

Vitamin D2 and D3 come from different sources, are metabolized differently, and have varying bioavailability and effects on our health.

A chart comparing the differences between Vitamin D2 and D3

Vitamin D2, also known as ergocalciferol, is made by plants and not naturally produced by our bodies. It's commonly added to foods like milk and cereals or found in supplements.

On the other hand, vitamin D3, or cholecalciferol, is made in our skin when we're exposed to sunlight and can also be obtained from certain animal-based foods like fatty fish, liver, and egg yolks.

In addition, each vitamin has a unique chemical structure that distinguishes them…

Vitamin D2 is formed when ergosterol, a compound found in fungi and plants, is exposed to sunlight. While D3 is produced when sunlight interacts with 7-dehydrocholesterol, a compound found in the skin of humans and animals (1).

Lastly, the source of vitamin D also plays an important role in how well our bodies absorb it…

Research shows that vitamin D3 is better at increasing overall vitamin D levels in the blood compared to D2.

This difference comes from how our liver processes these two forms and how they interact with vitamin D receptors in our body to support different biological functions.

Overall, while both forms can help meet vitamin D requirements, D3 might offer more reliable health benefits (2).

Are Their Health Benefits the Same?

Although vitamin D2 and D3 share differences in bioavailability, metabolism rate, and effectiveness of supplementation, they do share similar health benefits. Here are five, in particular…

Bone Health & Calcium Absorption

Both vitamin D2 and D3 are important for keeping your bones strong and sturdy. How? They help your body absorb calcium from the gut. Once vitamin D is converted into its active form called calcitriol, it helps your intestines absorb calcium and phosphate into the bloodstream. This is necessary for maintaining strong bones and teeth.

Additionally, vitamin D helps regulate calcium levels in the blood by stimulating the reabsorption of calcium in the kidneys and triggering the release of calcium from bones into the bloodstream when necessary. This function is essential in maintaining calcium balance and preventing conditions such as osteoporosis and rickets, characterized by weak or brittle bones. 

Research suggests that vitamin D3 might be more effective at maintaining optimal calcium levels and promoting bone health due to its superior absorption and longer-lasting effects (3).

Immune System Support

Vitamin D also plays a vital role in supporting the immune system. One of the ways it does this is by activating and regulating immune system cells, like T-cells, which are vital for the body's defense against pathogens. When there's an adequate level of vitamin D in the body, these cells can function optimally, leading to a more robust immune response. 

Conversely, a deficiency in vitamin D could impede the immune system's capability to effectively combat infections. In fact, numerous studies have linked vitamin D deficiency to an increased susceptibility to infections and autoimmune diseases. 

Although both D2 and D3 contribute to immune support, the higher bioavailability and longer duration of vitamin D3 in the bloodstream may suggest a more significant role in sustained immune system function (4).

Mental Health & Mood Support

Vitamin D has been associated with mental health and mood regulation. Studies have observed a correlation between low vitamin D levels and mood disorders such as depression and anxiety (5). The exact role vitamin D plays in mood regulation is not entirely understood, but it's thought to be linked to its effects on certain neurotransmitters like serotonin, often referred to as the “feel-good hormone”. 

However, more extensive studies are needed to establish definitive conclusions. It's always advisable to maintain a well-balanced diet, get sufficient sunlight, and consult with a healthcare professional for personalized advice on vitamin supplementation (6).

Heart & Cardiovascular Health

Additionally, some studies suggest a possible link between adequate vitamin D levels and cardiovascular health, with potential roles in blood pressure regulation and heart disease prevention (7).

Cognitive Function

Moreover, emerging research is exploring the potential role of vitamin D in supporting cognitive function, with implications for conditions like Alzheimer's and dementia (8).

So, Which Is Better: Vitamin D2 or D3?

When it comes to deciding which form of vitamin D is better—D2 or D3—it really depends on a few factors, including your diet, lifestyle, and personal health conditions.

Vitamin D3 comes from animal products, so it might not be vegan or vegetarian-friendly. On the other hand, D2 is plant-based. Both forms do a good job of increasing vitamin D levels in our blood, but D3 tends to keep those levels elevated for a longer time. Plus, D3 is known to be more effective in supporting bone health since it's easier for our bodies to absorb.

When making a decision between D2 and D3, you may also want to consider how easy and affordable it is to get each form. Depending on where you live, one might be more accessible or cost-effective than the other.

As for the recommended daily intake, The National Institutes of Health suggests (9):

  • Birth to 12 months: 10 mcg (400 IU)
  • Children 1 to 13 years: 15 mcg (600 IU)
  • Teens 14 to 18 years: 15 mcg (600 IU)
  • Adults 19 to 70 years: 15 mcg (600 IU)
  • Adults 71 and older: 20 mcg (800 IU)

The same values apply whether you're taking vitamin D2 or D3. However, these are general guidelines, and it's always recommended to seek advice from a healthcare professional based on your individual health profile and needs. They can guide you on which form of vitamin D may be best for you, the optimal dosage to take, and any potential interactions it may have with other supplements or medications you may be taking.

Lauren Manaker
Article by

Lauren Manaker

Lauren Manaker is an award-winning registered dietitian (RDN), certified lactation educator (CLE), author, and speaker with over 20 years of experience. She earned her BS in Food Science and Human Nutrition from the University of Florida (go Gators!) and an MS in Clinical Nutrition from Rush University in Chicago.

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    Medical Disclaimer

    This content is for informational and educational purposes only. It is not intended to provide medical advice or to take the place of such advice or treatment from a personal physician. All readers/viewers of this content are advised to consult their doctors or qualified health professionals regarding specific health questions. Neither Dr. Chad Walding nor the publisher of this content takes responsibility for possible health consequences of any person or persons reading or following the information in this educational content. All viewers of this content, especially those taking prescription or over-the-counter medications, should consult their physicians before beginning any nutrition, supplement, or lifestyle program.

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