Is your vitamin D supplement failing you?

The word is out: Most folks know they need vitamin D, and many are now taking supplements.

But are you REALLY getting what you need?

Odds are, you're NOT!

Sure, you might be taking the 2,000 to 5,000 IUs per day that I recommend to my own patients here at the Stengler Center for Integrative Medicine.

You might even be getting some sun each day to help your body produce its own D.

But new research reveals a "catch" when it comes to vitamin D, and it's something that I've shared with you before here in House Calls: Vitamin D can't work alone.

All of the supplements in the vitamin shop and all of the sun in the Sahara won't help much if you're missing out on magnesium.

You know that it's an essential mineral responsible for keeping your heart beating, your bones strong, and your muscles in shape.

But that's not all it can do.

Magnesium plays a key role in some 300 functions in the body, including a few that don't always get the attention they deserve.

A new study in the Journal of the American Osteopathic Association changes that.

It shines a light on how magnesium and vitamin D work together.

D by itself will pretty much go to sleep inside your body. It reverts to its inactive form, which is just what it sounds like.

It sits around, doing nothing.

When it does nothing, it's not just useless. It's dangerous, because "active" D is needed to help make sure calcium reaches the bone. When it's inactive, that calcium can stay in the blood, which eventually leads to calcification.

Magnesium is the alarm clock. It wakes up the D by converting it into the active form so that it can get to work moving calcium around -- not to mention all of its other functions, from heart protection to immune system support.

It's pretty easy to get the magnesium you need.

The problem, however, is that most people don't even come close.

The new study finds that 50 percent of Americans fall short in magnesium, which means that half the country can't get the right levels of active vitamin D even if they take a supplement.

If you're not taking a magnesium supplement yet, it's time to consider one. I find that magnesium glycinate is gentler on the stomach and more easily absorbed by the body than other forms.

Your doc can help figure out how much you need each day and how best to get it.