For years I've been writing to you about the benefits of spending 20 to 30 minutes a day in the sun without sunscreen. In just one 30-minute session, you can absorb up to 20,000 IUs of vitamin D.

But it turns out kids in the U.S. are staggeringly deficient. Earlier this month, researchers from the Albert Einstein College of Medicine of Yeshiva University discovered that 70 percent of kids had either "deficient" or "insufficient" levels of vitamin D in their blood.

Why does this not surprise me?

Well, for one, parents have been programmed to lather their kids in sunscreen even before heading outside. As a result, kids wind up getting most of their vitamin D from dietary sources.

But your child or grandchild drinks fortified milk. That's good, right?

Here again, many of us have been duped. This time by the powerful dairy industry. It wants parents to believe that if their child drinks fortified milk every day, they're getting enough vitamin D. But clearly -- as these new numbers show -- fortified milk just isn't enough.

The researchers estimate that 7.6 million children across the country are vitamin D deficient and another 61 percent, or 50.8 million, have insufficient levels of vitamin D. This can and will have serious consequences on the long-term health of these children.

We know vitamin D helps build strong bones. But it also does so much more. In fact, scientists have only begun to scratch the surface in understanding how important vitamin D is to our overall health. We are now discovering connections between vitamin D deficiencies and autoimmune diseases, heart disease, depression, and even cancer.

If you want to learn more about what parents can do to make sure their child has enough vitamin D, read this important Guide to Good Health from 10-23-08: