March is sure going out like a lion, isn't it? We had SNOW here in the Boston area just a few days ago!

After a seemingly never-ending winter, the sunnier skies of spring are sure going to be a welcome change -- at least, once they finally get here.

And once you finally get to catch some of those spring rays, it won't just brighten your outlook -- it'll also boost the levels of an essential vitamin in your body.

I'm talking about vitamin D, a.k.a. "the sunshine vitamin"!

Your body makes D when UV rays hit your skin -- and you need it for everything from strong bones to a healthy immune system.

But according to the latest research, all of the spring sunshine in the world won't net you enough D to get the job done if you're deficient in something else -- MAGNESIUM!

A new meta-analysis reviewed all available studies to date on the relationship between vitamin D and magnesium. And it turns out that all of the enzymes needed to "metabolize" vitamin D (in other words, to make it available for use in your body) require sufficient levels of magnesium.

That means that without enough magnesium in your system, any D you take in will simply sit "in storage" in your body... INACTIVE!

To put another way: You can take vitamin D supplements every day and STILL be deficient in D if you lack sufficient magnesium.

And that may actually make vitamin D supplementation dangerous -- because high levels of inactive D increase your calcium and phosphate levels, putting you at risk for "calcification" (a.k.a. hardening) of your arteries.

Beyond its role in activating D, magnesium also partners D in the delicate processes that protect your bones, heart, and organs.

On its own, magnesium is essential for a wide range of functions in your body, from promoting a good night's sleep to easing anxiety.

The bottom line is that you can't skimp on either one.

But a lot of folks do -- because nearly half of us are deficient in vitamin D, and a whopping 80 percent of us simply don't get enough magnesium in our diets.

You can boost your magnesium levels by loading up on magnesium-rich foods like dark leafy greens, nuts, seeds, fish, and avocado. Fatty fish like salmon and sardines will also up your stores of vitamin D, as will egg yolks and mushrooms.

But because it becomes harder for our bodies to absorb either of these nutrients from food (and, in the case of D, from sunlight) as we age, you should also consider taking high-quality supplements.

Many multivitamins contain enough D and magnesium to cover your bases. Read the labels closely and look for magnesium lactate and magnesium aspartate -- which are the forms most easily absorbed by your body -- and the natural vitamin D3 (rather than the synthetic D2).