Stay out of the sun... use sunscreen... cover up... wear a hat... nag, nag, nag.

I'm sick of it!

This bad advice has led directly to the vitamin D crisis and skin cancer explosion -- and now, a new study shows how it's destroying senior's lives, too.

Researchers say older Americans with the lowest levels of vitamin D have the highest risk for mobility problems... while those with the highest levels of the sunshine vitamin had the lowest risk.

Which category are you in? If you answered "highest," you're probably wrong. Most Americans are badly deficient, and it's getting worse every year.

Just look at this new study: The researchers tested 2,641 golden oldies with an average age of 75, and found two- thirds of them had insufficient D levels.

All of these seniors were asked to perform basic mobility tasks, such as walking 400 meters quickly, rising from a chair without using their arms, and some balance tests similar to what a cop might ask a DWI suspect to do.

The seniors were given the tests again two years later, and two years after that... and those with the highest D levels from the start did the best all the way through, according to the study presented at the Experimental Biology 2010 meeting.

The researchers say now they want to study whether D supplements can keep you out of the wheelchair, but let's call that what it is: An easy play for another research grant.

I can tell you right now what they'll find if they use high levels of genuine, natural vitamin D3: Healthy, active seniors. Vitamin D won't just boost your mobility, it will also lower your risk for diabetes, heart disease, bone breaks, cancer, colds, flu and more.

You can get your own quality supplement easily enough, but the best way to take in the D is to soak up the sun.

Just use a little common sense, don't get burned... and ignore the nags.