Women good health walking down forest trail sunlight for vitamin D

Vitamin D2 Versus D3 – 5 Things You Should Know Before You Buy

Picture this scenario. You are at a car dealership looking for a new car. You first lay eyes on a brand new Honda Accord. It has all the bells and whistles you could want. It looks good.

As you stand there, your gaze shifts slightly to the right where you notice a brand new Audi A8L, also with all the bells and whistles and coincidentally in your favorite color. It’s no surprise that it looks better.

However, it is not just an aesthetic value. A difference in the level of quality may be obvious at first glance but it is even more clear upon further investigation. And inevitably, the price tag reflects this.

Do you ever think about good versus better? In some scenarios better should always win out.

Your health is one such case. When considering supplementing with Vitamin D for all of its many health benefits, vitamin D2 may be good but D3 is certainly better. Here are 5 things you should know before you purchase your next vitamin D supplement.

Vitamin D key component to good health

1) D3 is the Most Natural Form of Vitamin D

It is likely you were not aware that Vitamin D came in more than one form. Chances are, however, you’ve heard that it comes from the sun. In fact, it is often referred to as the “sunshine vitamin.”

So what is the connection? The simple explanation is that your skin has a form of cholesterol in it that acts as a precursor to Vitamin D. When bare skin is exposed to the UVB rays of the sun, the energy converts the cholesterol to Vitamin D3.

It is the only form of the vitamin that is synthesized in the human body.

If getting enough daily sun is a challenge for you and you are considering supplementing with Vitamin D, be sure that it has the D3 form. The label might not list the number “3”, but you can also look for the scientific name of D3 which is Cholecalciferol.

2) D3 is the More Potent Form of Vitamin D

There are some conditions or scenarios that cause a deficiency in Vitamin D. In these cases, the more potent form – D3 – should be the preferred treatment.

Research shows that D3 is 87% more potent than D2, which results in 2 – 3 more times storage of Vitamin D.(1) This is critical for those who might struggle with the ability to produce, absorb, or store the necessary amounts of Vitamin D for good health.

Vitamin D3’s increased potency would be especially helpful in these situations:

  • Older adults – because their skin does not convert to vitamin D as efficiently
  • Obesity – because fat binds to D preventing it from getting into the bloodstream
  • Dark skin – because larger amounts of melanin prevent skin from converting the sun to Vitamin D as efficiently
  • People taking cholesterol drugs, antifungal drugs, or seizure medications – because these meds adversely affect bone mineral density
  • Anyone with Crohn’s or Celiac disease – because they do not handle fat as well
Middle aged black women vitamin D3
Struggle to produce aborb store vitamin D

3) D3 is Less Toxic in Higher Concentrations

If you have spent any time looking into taking vitamins, then you might know that they fall into two categories – water soluble and fat soluble. Vitamins B and C are water soluble, do not store in the body, and are excreted in the urine. Vitamins A, D, E, and K are usually absorbed into fat globules and stored in the body for future use.

It is this difference that, at times, has given the fat soluble vitamins a reputation for being dangerous.

D2 has more impurities and is less stable, so this poses a higher risk when concentrations are elevated.(2) And it turns out that excess D2 is more likely to circulate freely in the blood because it does not bind as well to Vitamin D receptors as D3 does.

4) D3 Has a Longer Half Life in the Body

Half life is the scientific term for how long it takes half the amount of a substance to metabolize or break down.

Vitamin D2’s half life is shorter than D3’s since it does not bind as well to the D receptors in the body. So it doesn’t have as much time to do it’s job before it makes its way out of your body. (3)

Once again, it is an issue of good versus better. D2 does not give you the same “bang for your buck” that D3 does.

5) D3 Has a Longer Shelf Life in the Store

When you purchase that bottle of Vitamin D in the store or online, you usually have no idea how long it has been sitting on the shelf. You can check the expiration date which might give you an idea of how much longer it will be effective. However, there is really no way for you to know if it was exposed to varying levels of temperature and humidity in transport or storage.

D3 is the better choice because it is more stable than D2 in the face of adverse conditions – giving it a longer shelf life.(4)

Compelling Reasons to Include D3 in Your Routine

Vitamin D thinking woman sitting on park bench beside tress
Vitamin D slows diseases and conditions

If you grew up in the baby boomer generation, then you probably heard that vitamin D was essential for healthy bones. Thanks to the discovery in the 1930’s that finally connected vitamin D deficiency to the cause of the rampant bone disease called rickets, D became known as the “healthy bones” vitamin.(5)

Decades later, we now know that vitamin D plays a key role in preventing and/or slowing many other diseases and conditions.

Here are several compelling reasons to include D3 in your routine:

  • Reduces your risk of Multiple Sclerosis (6)
  • Decreases the risk of Cardiovascular Disease (7)
  • Reduces the chances of catching the flu (8)
  • Has a positive effect on insulin resistance in Type II diabetes patients (9)
  • May reduce risks of dementia and Alzheimer’s disease (10)
  • Some research suggests it may help to prevent risks of certain cancers (11)

Reasons That D Deficiency is So Common

At first glance, it may be surprising to know that more than half the population is deficient in vitamin D – despite the fact that it is a free and natural result of the sun.

The extensive use of sunscreen is one reason why many people are not getting their daily dose of D, since sunscreen reduces your body’s production of D by 99%.

Lifestyle choices and/or jobs that keep us indoors all day are another reason that D deficiency is quite prevalent.

Certainly, in places that have colder climates, there is a higher incidence of people not getting enough of this important vitamin.

Nutritionally poor diets and strict vegan diets also make it difficult to keep vitamin D levels in the healthy range. The foods that naturally contain vitamin D such as salmon, tuna, beef liver, and egg yolks are not typically part of a vegan diet and rarely make an appearance in an unhealthy diet.

These are all reasons that supplementing with vitamin D3 becomes paramount to maintaining and achieving optimal health.

Final Thoughts Regarding Vitamin D3

Woman on hotel bed using macbook Vitamin D3 research
Poor and vegan diests may cause low vitamin D

We live in a time where we get constantly inundated with health information. It would be easy to get overwhelmed and make quick easy choices based on what you read or hear. In some cases, you might be taking a good step. However, the better step is to do your research and then make quality choices based on all the facts.

Taking a vitamin D that utilizes the D3 form is the better choice for your immediate and long-term health. Always err on the side of better when it comes to your good health.


1) Heaney, RP and Recker, RR and Grote, J and Horst, RL and Armas LA (2011) Vitamin D(3) is more potent than vitamin D(2) in humans. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/21177785

2) Houghton, Lisa A and Vieth, Reinhold (2006) The case against ergocalciferol (vitamin D2) as a vitamin supplement.Retrieved from http://ajcn.nutrition.org/content/84/4/694.full

3) Jones, KS and Assar, S and Harnpanich, D and Bouilon, R and Lambrechts, D and Prentice, A and Schoenmakers, L (2014) 25(OH)D2 half-life is shorter than 25(OH)D3 half-life and is influenced by DBP concentration and genotype.Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/24885631

4) Houghton, LA and Vieth R (2006) The case against ergocalciferol (vitamin D2) as a vitamin supplement. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/17023693

5) Rajakumar, K (2003) Vitamin D, cod-liver oil, sunlight, and rickets: a historical perspective. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/12897318

6) Munger, Kassandra L and Levin, Lynn L and Hollis, Bruce W (2006) Serum 25-Hydroxyvitamin D Levels and Risk of Multiple Sclerosis. Retrieved from http://jamanetwork.com/journals/jama/fullarticle/204651

7) Judd, Suzanne and Tangpricha, Vin (2008) Vitamin D Deficiency and Risk for Cardiovascular Disease. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2726624/

8) Urashima, M and Segawa, T and Okazaki, M and Kurihara, M and Wada, Y and Ida, H (2010) Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/20219962

9) Afsaneh, Talaei and Mahnaz, Mohamadi and Zahra, Adgi (2013) The effect of vitamin D on insulin resistance in patients with type 2 diabetes. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3586569/

10) Littlejohns, Thomas J and Henley, William E and Lang, Iain A and Annweiler, Cedric and Beauchet, Olivier and Chaves, Paulo H. M. and Fried, Linda and Kestenbaum, Bryan R and Kuller, Lewis H and Langa, Kenneth M and Lopez, Oscar L and Kos, Katarina and Soni, Maya and Llewellyn, David J (2014) Vitamin D and the risk of dementia and Alzheimer disease. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4153851/

11) Garland, Cedric F and Garland, Frank C and Gorham, Edward D and Lipkin, Martin and Newmark, Harold and Mohr, Sharif B and Holick, Michael F (2006) The Role of Vitamin D in Cancer Prevention. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1470481/

Steve Sisskind, M.D.

Hi, I'm Dr. Steve Sisskind, Chief Medical Officer & Founder at RealDose Nutrition.

As a young physician, I struggled. My patients came to me with serious health issues, but I didn't have the tools to help them. Medical school taught me how to put "band aids" on their symptoms with drugs and surgery, but not how to address the root causes of their problems.

Years later I discovered a better approach... based on the fundamental idea that "you are what you eat."

The good news is that anyone can use the power of nutrition to transform their health and vitality. But there's a lot of confusion. What foods should I eat? Which supplements should I take? What does the science say?

I have dedicated my life to answering these questions... to discovering the best path to amazing health and vitality through nutrition. And I share this knowledge with you every day here at RealDose Nutrition.

I invite you to connect with me by joining my free private community. I've helped thousands of people and I know I can help you too!

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