Be Sure to Avoid This Kind of Vitamin D Supplement

And since D3 is the form your body naturally makes from sunlight, and the one shown to be more effective for overall health, this is an important distinction.

The research, published in Nutrition Reviews, analyzed multiple clinical trials. 

People taking vitamin D2 not only failed to see the same benefits as those taking D3, but in many cases, their D3 levels dropped below baseline.

On the other hand, vitamin D3 supplementation was far more effective at raising and maintaining healthy vitamin D status.

Why does this matter? 

Beyond bone health, vitamin D3 plays a special role in immune defense. 

Previous work from the same group demonstrated that D3 helps activate the body’s type I interferon system, a crucial early defense against viruses and bacteria. 

In other words, vitamin D3 doesn’t just keep bones strong. It may also help your immune system stay resilient when you’re exposed to seasonal bugs.

The takeaway is simple: while both forms are technically “vitamin D,” they are not interchangeable. For most people, vitamin D3 is the form that offers the clearest benefit for immunity and overall health.

As always, supplementation should be tailored to your individual needs, but if you’re choosing between D2 and D3, the evidence strongly favors D3.