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1 In 7 Teens Deficient In Vitamin D

Posted on: Thursday, 12 March 2009, 07:20 CDT

A new study finds that one in seven American adolescents is deficient in vitamin D, something that could raise the risk of high blood pressure, high blood sugar and metabolic syndrome.

In the study, which highlights the association between high levels of vitamin D and lower risk of heart disease, researchers in the Department of Public Health at Weill Cornell Medical College analyzed 3,577 adolescents aged 12 to 19 years old, 51 percent of which were boys. The ethnic breakdown was similar to the general U.S. population: 64.7 percent non-Hispanic whites; 13.5 percent non-Hispanic blacks; and 11 percent Mexican Americans. All had participated in the nationally representative National Health and Nutrition Examination Survey (NHANES) conducted from 2001–2004.

After adjusting for age, sex, race/ethnicity, body mass index, socioeconomic status and physical activity, the researchers found that adolescents with the lowest levels of vitamin D were 2.36 times more likely to have high blood pressure, 2.54 times more likely to have high blood sugar, and 3.99 times more likely to have metabolic syndrome.

Metabolic syndrome is a cluster of cardiovascular disease and diabetes risk factors including 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 three or more of these factors increases a person’s risk of developing diabetes and cardiovascular disease.

“We showed strong associations between low levels of vitamin D and higher risk of high blood pressure, hyperglycemia and metabolic syndrome among adolescents, confirming the results of studies among adults,” said Jared P. Reis, Ph.D., the study’s lead author and post-doctoral research fellow at Johns Hopkins Bloomberg School of Public Health in Baltimore.

Researchers used a biomarker of vitamin D to measure levels in the blood. The biomarker measures vitamin D obtained from food, vitamin supplementation and exposure to sunlight.

The highest levels of vitamin D were found among whites, while the lowest levels were observed in blacks and intermediate levels in Mexican Americans.

Whites had average vitamin D levels of 28.0 nanograms per milliliter (ng/mL);  almost twice that of blacks, who averaged 15.5 ng/mL.  Hispanics had average vitamin D levels of 21.5 ng/mL.

The study employed a new definition of vitamin D deficiency recommended by a group of scientists attending the 13th Workshop Consensus for Vitamin D Nutritional Guidelines in 2007. These experts collectively proposed that the minimum acceptable serum vitamin D level be raised from 11 nanograms per milliliter (ng/mL) to at least 20 ng/mL.

Under the newer criteria, the study found that more than half of the African-American teens are vitamin D deficient.  Furthermore, girls had more than twice the risk of deficiency than did the boys, while overweight teens had nearly double the risk of their normal-weight counterparts.

"These are alarming findings. We need to do a better job of educating the public on the importance of vitamin D, and the best ways to get it,” said Dr. Sandy Saintonge, assistant professor of clinical pediatrics and assistant professor of clinical public health at Weill Cornell Medical College.  

“To meet minimum nutritional requirements teens would need to consume at least four glasses of fortified milk daily or its dietary equivalent. Other foods rich in vitamin D include salmon, tuna, eggs and fortified cereals. A vitamin supplement containing 400 IU of vitamin D is another alternative.”

"We should also consider a national fortification strategy, perhaps including routine supplementation and monitoring of serum levels, but more research is needed to determine optimal vitamin D levels,” he said.

“Although our study is important, we believe clinical trials designed to determine the effects of vitamin D supplementation on the risk of heart disease risk factors in adolescents should be conducted before recommendations can be made for vitamin D in the prevention of cardiovascular disease,” Reis said in a press release about the study.

The Institute of Medicine recommends a daily intake of vitamin D of 200 International Units (IU) for those less than 50 years, which includes children and adolescents.  However, recent recommendations from the American Academy of Pediatrics suggest a daily intake of 400 IU, and some experts suggest intakes of at least 1,000 I.U. for overall health. 

Vitamin D deficiency can interfere with bone mineralization, leading to rickets, in children.   In adults, it is linked to cardiovascular disease, cancer, diabetes, immune dysfunction and hypertension.

Of the specific findings, the authors were particularly concerned about the role of weight in deficiency.

Low levels of vitamin D are strongly associated with being overweight and abdominal obesity.   Since vitamin D is a fat-soluble vitamin, it may be sequestered within adipose tissue, something that might explain why those who are obese are more likely to be vitamin D deficient, Reis said.

Senior author Dr. Linda Gerber shared Reis’ concern.

"Because vitamin D is stored in body fat, simply increasing the dosage of vitamin D may not be effective in overweight adolescents," said  Gerber, professor of public health in the Division of Biostatistics and Epidemiology and professor of epidemiology in medicine at Weill Cornell Medical College.

"As the prevalence of childhood obesity increases, vitamin D deficiency may increase as well. In this group, appropriate nutrition could solve both problems."

Vitamin D plays a useful role in general human health, particularly in bone health, and other roles are now 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,” he said.

“These data on serum vitamin D levels in young people raise some concern about their food choices and even the amount of time they spend in the sunshine,” said Robert H. Eckel, M.D., American Heart Association past president.

“The American Heart Association recommends an overall healthy diet and lifestyle, and that people get their nutrients primarily from food sources rather than supplements.”

The findings were published in the March issue of the journal Pediatrics, and were presented at the Pediatric Academic Societies' Annual Meeting in May 2008 and the American Heart Association’s 49th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.
 
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On the Net:

• Weill Cornell Medical College
• Johns Hopkins Bloomberg School of Public Health
• Institute of Medicine
• American Academy of Pediatrics
• Pediatrics

Source: redOrbit Staff & Wire Reports

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