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The Worst Vitamin D Supplement To Take, Say Dietitians

To make the most out of your supplementation routine, skip this type of vitamin D.
FACT CHECKED BY Olivia Tarantino

Did you know there are several forms of vitamin D available in food and supplements? This is actually true for several different vitamins, and it's important to keep in mind when incorporating and vitamin supplements into your daily routine.

Not all forms of vitamin D are created equal, and, in fact, there is one form that stands above the rest. And because there's one type of vitamin D that's considered to be the best, that also means there's a vitamin D supplement that dietitians consider to be less effective, or in other words, the "worst": vitamin D2.

Here is what you need to know about the different forms of vitamin D before you head to the store to pick out your supplements.

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What is vitamin D and what are the different types?

Vitamin D is unique because it is a vitamin that we can create in our body as long as our skin is exposed to UV-B rays from the sun. Despite this, many adults are deficient in vitamin D and rely on supplements to supply their body adequate amounts.

There are two main forms of vitamin D: D2 (ergocalciferol) and D3 (cholecalciferol).

D3 is the form that is created in your body and is also naturally found in animal-based foods, like fish, eggs, and animal liver, while D2 is found naturally in plant-based foods, like mushrooms. Both forms can be consumed through supplements; however, the D2 form is more frequently used in fortified foods, like cereal and dairy products, and supplements because it is less expensive to produce.

While both forms of vitamin D contribute to the "pool" of vitamin D available in your body, D2 is considered to be less effective than D3. Because of this, vitamin D2 is a less desirable form of vitamin D and should not be your first choice for a supplement.

Why vitamin D2 should not be your vitamin D supplement of choice.

vitamin d in the sun

Of course, when incorporating a supplement into their daily routine in an effort to improve vitamin D status, many people are interested in the best bang for their buck. And as mentioned earlier, vitamin D2 is less expensive to produce than vitamin D3, so you may be drawn to buying it due to its lower price tag. However, in order to get the most out of your vitamin D supplement, skip D2 and head straight for D3.

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In addition to being less effective at raising levels of blood vitamin D content, vitamin D2 supplements may also be of lower quality than their D3 counterparts. Research has found that D2 is more likely to degrade over time if exposed to varying temperatures and humidity, likely yielding an even less effective supplement.

How to buy the best vitamin D supplement

Luckily, when choosing a vitamin D supplement, most labels will include the form of vitamin D that has been used within the product, either D2 or D3, so you are well informed and can choose products accordingly.

While all forms of vitamin D supplements can help improve your vitamin D status to some extent, it is in your best interest to choose D3 for maximum effectiveness.

In addition to consuming a supplement, you should also increase your intake of D2 and D3 rich foods, and aim to spend time outdoors each day to aid in improving your vitamin D status.

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Melissa Rifkin, MS, RDN, CDN
Melissa is a Connecticut-based registered dietitian with over 15 years of experience, including clinical and outpatient settings, and runs the popular nutrition education Instagram account, Confessionofadietitian. Read more about Melissa