Scientists have known for some time that in adults, low levels of vitamin D are associated with high blood pressure, high blood sugar and metabolic syndrome — a collection of risk factors for diabetes and heart disease that includes high waist circumference and elevated cholesterol and triglycerides. Now we know that too little of the sunshine vitamin causes those same problems in tweens and teens.

Kids ages 12 to 19 with the lowest levels of vitamin D (less than 15 nanograms per milliliter) were more than twice as likely to have high blood pressure and blood sugar, and nearly four times as likely to have metabolic syndrome as those with the highest amounts (more than 26 nanograms per milliliter), according to research presented yesterday at this week's American Heart Association Conference on Cardiovascular Disease Epidemiology and Prevention in Palm Harbor, Fla. Levels of 30 nanograms per milliliter are considered sufficient. The results are based on 3,577 teens who participated in the National Health and Nutrition Examination Survey (NHANES) conducted between 2001 and 2004.

Black and Hispanic teens were more likely to be vitamin D-deficient than whites. (Darker-skinned people have more melanin, a pigment that blocks the sun's UVB rays and makes it harder for them to produce vitamin D.)  The  study didn’t  examine whether they also were more likely to suffer from the associated vitamin D-deficient conditions;  previous research has found that African-American kids experience higher rates of hypertension and Mexican-American teens have higher fasting glucose levels than their white and black counterparts.

What does vitamin D have to do with heart health? It may affect the ability of blood vessels to relax and contract as the body maintains blood pressure, study author Jared Reis, a post-doctoral research fellow at the Bloomberg School of Public Health, tells And people with more vitamin D are better able to move glucose from food into cells and use it for energy, which could lower their risk of metabolic syndrome.

"We're not saying vitamin D causes these things, but that there's an association," Reis says. "It makes you wonder about how much time kids are playing outside and their diet in terms of adequate amounts of vitamin D. [In addition] African Americans have higher rates of hypertension compared to whites and to have lower vitamin D levels, so it makes you wonder if vitamin D is contributing to their increased risk."

The findings are the latest in a string of studies suggesting links between vitamin D deficiency and ill health, including more colds and Cesarean-section deliveries in people with a lack of it.

Image © iStockphoto/Robert Simon