Lower levels of vitamin D in teenagers are associated with a greater risk of high blood pressure, heart disease and high blood sugar, reports a new U.S. study.

The "sunshine" vitamin is needed for the development and maintenance of strong bones, but the new study has found an association between vitamin D and other possible health benefits. The research involving teenagers confirms the results that have been seen in adults, linking low levels of vitamin with risk factors for heart disease, the scientists said.

In the new study, researchers looked at 3,577 adolescents, with the ages between 12 and 19 years old - 51 per cent being boys. All the participants took part in the nationally representative National Health and Nutrition Examination Survey (NHANES), conducted from 2001 to 2004. After taking into consideration factors such as age, gender, race/ethnicity, BMI (body mass index), socioeconomic status and levels of exercise, the experts found that, compared to the 25 per cent of adolescents with the highest levels of vitamin D in their blood, the 25 per cent of the adolescents with the lowest levels of vitamin D had:

• 2.36 times greater risk to develop high blood pressure;

• 2.54 times greater risk to develop high blood sugar; and

• 3.99 times greater risk to develop metabolic syndrome.

Metabolic syndrome is a combination of cardiovascular disease and diabetes risk factors that include elevated waist circumference, high blood pressure, elevated triglycerides, low levels of high-density lipoprotein (HDL or "good") cholesterol and high fasting glucose levels. The presence of 3 or more of the factors increases a person's risk of developing diabetes and heart-related problems.

We found a strong link between insufficient levels of vitamin D and an increased risk of high blood pressure, hyperglycemia and metabolic syndrome among teenagers, which coincides with the results of studies among adults, said Jared P. Reis, Ph.D., a lead investigator of the study and post-doctoral research fellow at Johns Hopkins Bloomberg School of Public Health in Baltimore.

Researchers used a biomarker of vitamin D to measure its levels in blood. The biomarker measures vitamin D taken from food, vitamin supplements and exposure to sun. The ethnic breakdown was similar to the general population in the United States: 64.7 per cent non-Hispanic whites; 13.5 per cent non-Hispanic blacks; and 11 per cent Mexican Americans. The highest levels of vitamin D were found in white teenagers, the lowest levels in African Americans and intermediate levels in Mexican American teens. Black teens averaged about half the vitamin D levels seen in white teens. In whites, the average level of vitamin D was 28.0 nanograms per milliliter (ng/mL), in black teens - 15.5 ng/mL, and in Mexican Americans - 21.5 ng/mL.

The Institute of Medicine recommends a daily intake of vitamin D of 200 International Units (IU) for individuals under 50 years of age, as well as for children and adolescents. However, the American Academy of Pediatrics recently doubled the recommended amount of vitamin D for children and teens to 400 units per day - the equivalent of drinking four cups of milk. The pediatricians group said that children who do not drink enough milk, should take vitamin supplements.

Low levels of vitamin D are strongly associated with overweight and abdominal obesity. Since vitamin D is a vitamin that dissolves in fat, it may be disappearing within adipose tissue. This may explain why people who suffer from obesity are more likely to be vitamin D deficient, Dr. Reis explained. Vitamin D plays an important role in overall human health, and, in particular, in bone health. Other roles are emerging, Reis said. "This is an exciting time, since we are just now beginning to understand the role that vitamin D may play in cardiovascular health."

The study was presented at the American Heart Association's 49th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.

Tags: Vitamins, Diabetes, Heart Disease

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