Vitamin D deficiency afflicts millions of US children and increases their risk for bone disorders, diabetes and cardiac disease, according to 2 new studies.

In the first study, Michal Melamed and colleagues from Albert Einstein College of Medicine found that 9% of those between ages 1-21 had Vitamin D levels low enough to be called deficient. That’s 7.6 million children, adolescents and young adults.

An astounding 61% more– nearly 51 million people–have slightly below normal levels.  “At first, we couldn’t believe the numbers,” said Melamed. “It’s very worrisome.”

In their nationally representative sample of 6,000 children, the scientists found that girls, adolescents and African Americans were at particular risk. A whopping 59% of teenage African American girls were Vitamin D deficient.

“This appears to be another result of our unhealthy lifestyles, including a sedentary society that doesn’t go out in the sun much,” Melamed told the Washington Post.

The scientists said contributing factors included kids spending too much time watching TV and playing video games, use of long-sleeves and sunscreen when they do go out, and substituting soda for milk and Vitamin D fortified foods.

Ominously, the study revealed that low Vitamin D levels were associated with hypertension and metabolic syndrome, a precursor of diabetes.

In the second study, the NHLBI’s Jared Reis confirmed that Vitamin D deficient individuals were at greater risk for hypertension, hyperglycemia and metabolic syndrome.  Both studies support earlier reports from Weill Cornell Medical College.

Recently, an expert panel representing the American Academy of Pediatrics recommended markedly increased dietary intake of Vitamin D. The IOM is conducting a review of federal guidelines on the same matter.