An eye-popping 70 percent of kids have too-low levels of vitamin D, according to a new study announced Monday.

From a WebMD article:

Seven out of 10 U.S. children have too-low vitamin D levels, putting them at risk of heart disease, rickets, and weak bones.

Nearly one in 10 kids -- 7.6 million American children -- are actually deficient in vitamin D. Vitamin D deficiency is a serious health threat in which the body begins to reabsorb calcium from the skeleton.

The new findings come in a study by Juhi Kumar, MD, MPH, of Montefiore Medical Center; Michal Melamed, MD, of Albert Einstein College of Medicine; and colleagues.

"We expected the prevalence of vitamin D deficiency would be high, but the magnitude of the problem nationwide was shocking," Kumar says in a news release.

Rickets, a bone disease of infants and children caused by too little vitamin D, has been on the rise. It's not the first time: A U.S. epidemic of rickets at the end of the 1800s ended only when the U.S. fortified milk with vitamin D.

It's now apparent that more must be done.

My own history with vitamin D, which I have written about on my Neurotic Mom blog, is a good illustration of why parents should trust their instincts. I've been concerned about my kids' vitamin D levels, as well as my own, since 2004, when I first read of a link between low vitamin D levels and multiple sclerosis, which runs in my family and which I'm terrified of getting, or of my kids getting. At the time, I was giving Belle Tri-Vi-Sol drops, which then contained 200 international units of vitamin D, even though her doctor said not to. I felt like I was breaking the law; indeed, it was the first piece of medical advice that I didn't follow as a parent.

As she got older, we started giving her a chewable multivitamin, which also contained 200 IU of vitamin D, and when Wes was born, I intended to start him on the drops. But again our pediatrician warned against it, this time saying vitamin supplements in infancy had been linked with an increase in allergies and asthma. He recommended instead that we just make sure Wes got some sunlight every day.

That winter, 2006-07, I was diligent about getting Wes outside for his requisite 20 minutes of sunshine. I remember some of the coldest days — days so cold even Belle wouldn't go out to play in the snow — bundling Wes up in the stroller so that only his little face peered out, and walking him up and down the sidewalk in front of our house. Each time we turned around and walked away from the sun, I pulled him backwards so he'd still be facing it, and I know people driving by thought I was crazy.

As he got closer to turning 1, we started giving him the vitamin drops with 200 IU of D.

In October 2008, the American Academy of Pediatrics doubled its recommendation for a daily dose of vitamin D, saying children should get 400 IU per day. I immediately kicked myself for giving them only 200 IU when, after reading all this research, I knew they probably needed more.

Since then, they've both been getting 400 IU per day in their multivitamin.

The frustrating thing about this issue is that, as important as vitamin D is becoming, children don't have their levels tested as a matter of course, as with iron and lead. I even requested once to have Belle and Wes tested but was discouraged by our pediatrician.

Despite not getting enough D in supplements, Belle and Wes are probably OK because I'm lax about putting sunscreen on them, especially after reading this article that weighs the risks of getting skin cancer versus the cancer-fighting benefits of vitamin D. Our kids both tan easily, like me, and they've never had a sunburn. Being darker skinned also means it's harder for our bodies to make D, so we need more time in the sun. Therefore I really only slather them head to toe with sunscreen when they're going to be out in the mid-day sun; otherwise I just put it on their faces.

The WebMD article recommends giving children some sunscreen-free time outside (unless they burn easily):

Melamed noted that the widespread use of sunscreens keeps kids from getting vitamin D from sunlight.

"It would be a good idea for parents to turn off the TV and send their kids outside," she says in the news release. Just 15 to 20 minutes a day should be enough. And unless they burn easily, don't put sunscreen on them until they've been out in the sun for 10 minutes, so they get the good stuff but not the sun damage."

Other ways to get vitamin D:

* Multivitamins, or vitamin D-specific supplements like these, which I've seen at Arbor Farms and Whole Foods.

* Vitamin D-rich foods, such as salmon and other fatty fish, and eggs.

* Fortified foods, such as milk, orange juice and cereal.

Here's a great fact sheet on vitamin D, with information on how much you can get from food sources, from sunlight, and from supplements.

Jen Eyer is on the Community Team at AnnArbor.com. She can be reached at 734-623-2577 or jeneyer@annarbor.com, or you can visit her at the first floor office at 301 East Liberty.