Researchers analyzed 11 trials with 655 adults and discovered that taking vitamin D2 supplements decreases the body's vitamin D3 levels, a previously unknown effect.

That’s because our body doesn’t make enough of the stuff in the darker months as sunlight decreases. Vitamin D is key to ...

Learn how vitamin D functions and may affect diabetes, heart disease, cancer, and dementia risk. Plus, how it could benefit your mood and bones.