Sunscreen and spending less time in the sun are contributing factors to the vitamin D deficiency crisis, researchers say.

RODALE NEWS, EMMAUS, PA—An astounding 70 percent of children in the United States have low levels of vitamin D, raising their risk of bone and heart disease, according to a new study. The extent of problem can be attributed to lack of unprotected time in the sun and the fact that vitamin D is found in ample amounts in very few foods.

THE DETAILS: Researchers looked over data, including blood levels of vitamin D, from more than 6,000 children and young adults ages 1 to 21, collected by the National Health and Nutrition Examination Survey from 2001 to 2004. They found that 9 percent of those studied (7 million) were vitamin D deficient; another 61 percent (21 million) were vitamin D insufficient. "We expected the prevalence of vitamin D deficiency would be high, but the magnitude of the problem nationwide was shocking," says lead author Juhi Kumar, MD, MPH, a fellow in pediatrics at The Albert Einstein College of Medicine. Darker-skinned and obese children, and those who drank less than a glass of milk a week, were more likely to have low levels.

WHAT IT MEANS: Vitamin D has long been hailed as an important nutrient because it helps your body absorb calcium. But more and more research is linking insufficient vitamin D levels to diabetes, cardiovascular disease, and even some cancers. According to the study authors, children are spending more time inside playing video and computer games, or are wearing sunscreen when they are outside. This inhibits the body from using sunlight to make the vitamin naturally. Couple that with the fact that it's very difficult to get enough of the vitamin from food and drinks alone, and it's easy to see how kids came to be so deficient. Other studies have found that more than half of the country’s adult population is significantly low in D, too.

Here's how kids and adults can boost their levels of this very important vitamin.

• Know how much to get. The American Academy of Pediatrics recently doubled the amount of vitamin D all children (including breastfed infants) should get every day. The new guidelines suggest 400 IU a day, starting within the first few days of life. Most experts agree adults should take in 1,000 to 1,400 IU a day, too.

• Supplement for optimum D levels. There are two types of vitamin D: vitamin D2 and D3. Choose the latter because your body more readily uses this form. For children who won’t easily take a vitamin D pill, look for vitamin D in liquid form.

• Get some from food. For extra coverage, kids and adults can acquire some vitamin D from fatty fish, such as mackerel, sardines, or salmon (Alaskan wild-caught is best from an environmental and health standpoint), egg yolks (we don't recommend too much of these or you could raise your cholesterol), and fortified milk, and cereals. However, it's really hard to get enough of the vitamin through food alone.

• It's your call when it comes to the sun. Researchers say the vitamin D problem is getting worse because children are spending little unprotected time in the sun. The author of this study suggests children who don't burn easily should spend 10 minutes of unprotected time in the sun a few times a week to spark enough natural vitamin D production. However, spending too much time in the sun can also lead to skin cancer and melanoma. Also note that in areas north of Atlanta, the sun's rays aren't strong enough in fall and winter months to create this conversion, so supplements are necessary. However you decide to handle your child’s and your own exposure to sunlight, it's best to take supplements year-round.