(NaturalNews) Even teenagers living in the southern United States still suffer from widespread vitamin D deficiency, according to a study conducted by researchers from the Medical College of Georgia.
"Our data demonstrate that low vitamin D status is common among adolescents residing in the southeastern region and is related to various adiposity and lifestyle factors," the researchers wrote. "Taken together, these findings suggest that low vitamin D status is a growing national problem for adolescents in the United States, regardless of latitude."
Because the body synthesizes vitamin D upon exposure to sunlight, researchers have long known that people living far from the equator tend to be at greater risk of deficiency.
Researchers tested the vitamin D blood levels and recorded the cardiovascular fitness and physical activity habits of 559 high-school students from the Augusta, Ga. area between the ages of 14 and 18 from January 2001 and June 2005. They also calculated several different measures of body fat for each participant, including body mass index (BMI), waist circumference, total fat mass, percent body fat, and subcutaneous abdominal and visceral adipose tissue.
A total of 56.4 percent of the teenagers had insufficient levels of vitamin D, while 28.8 percent were deficient. Insufficiency was defined as having less than 75 nanomols of the vitamin per liter, while deficiency was defined as less than 50 nanomols per liter. These levels are higher than those normally set as deficiency thresholds.
After adjusting for confounding factors such as age, gender, height, race, season and sexual maturity, the researchers found that all measures of body fat were significantly associated with a higher risk of deficiency. Conversely, higher levels of activity and higher cardiovascular fitness were associated with a lower risk.
Black students had significantly lower blood levels of vitamin D in all students than white students did, and were significantly more likely to be deficient.