OLD GREENWICH, CONN. — Vitamin D deficiency, sometimes quite severe, is common in obese adolescents, according to a recent study by Dr. Margarita Smotkin-Tangorra and colleagues at Maimonides Medical Center, N.Y.
Speaking at a meeting of the Eastern Society for Pediatric Research, Dr. Smotkin-Tangorra, of the department of pediatric endocrinology and diabetes at the medical center, said that 55% of a cohort of 217 obese children and adolescents were deficient in serum 25-hydroxyvitamin D (25-OHD), with blood levels of less than 20 ng/mL; 22% were severely deficient, with serum levels below 10 ng/mL.
Though there are published reports showing correlations between vitamin D deficiency and obesity in adults, there are no prior studies in children or teens. “We know vitamin D deficiency is prevalent in all age groups, including healthy adolescents. In obese adults, we know that it correlates with insulin resistance, progression to diabetes mellitus, metabolic and endocrine problems, and increased risk of cancer. We wanted to see if there were similar correlations in obese kids,” she told attendees at the meeting, cosponsored by Children's Hospital of Philadelphia.
The study group included 118 females and 99 males, ranging in age from 7 to 18 years, and with a mean BMI of 32.2 kg/m
They found strong correlations between low vitamin D level and elevated BMI, increased systolic blood pressure, lower HDL, and lower alkaline phosphatase.
The correlation between vitamin D status and BMI was particularly striking. Those patients who were vitamin D deficient had a mean BMI of 36.2, compared with a mean of 30.6 among patients whose vitamin D levels were sufficient.
The association with systolic hypertension was also noteworthy; vitamin D-deficient patients had a mean systolic blood pressure of 117 mm Hg, while those with sufficient vitamin D had a mean systolic blood pressure of 111 mm Hg. Mean HDL was 40 mg/dL in the vitamin-deficient group, compared with 42 mg/dL in the vitamin-sufficient group.
There was no correlation between vitamin D status and fasting blood glucose or thyroid hormone levels. Insulin sensitivity as indicated by a quantitative insulin sensitivity check index score showed a marginally significant correlation with vitamin D, with the deficient children showing a slightly lower score than the sufficient ones.
Vitamin D deficiency is disturbingly common, even among healthy children. Best current estimates are that roughly 20% of all school-age children are deficient. If Dr. Smotkin-Tangorra's data prove to be representative of obese children nationwide, the problem may be greater than previously imagined, especially given what is now known about the long-term impact of chronic vitamin D deficiency.
Increased prevalence of deficiency reflects several general trends, most importantly the diminishing quality of children's diets and lack of outdoor exercise. How it fits into the pathophysiology and etiology of obesity is an open-ended question at this point. Lower levels of vitamin D could well be an indicator of poor overall nutritional status. Dr. Smotkin-Tangorra's team did not study blood levels of any other vitamins or minerals, but their research suggests that the more obese a child is, the more likely that the child's overall nutritional status will be poor.
Vitamin D deficiency is one of the few common correlates of childhood obesity that is easy to rectify. “We are routinely supplementing all of our obese kids with Os-Cal, 500 mg, thrice daily, and we are starting to collect data on the outcomes.” She advised clinicians working with children and adolescents to stay vigilant for vitamin D deficiency, especially in obese patients, and to supplement with vitamin D and calcium when the levels are low. There's little risk, it is inexpensive, and the potential long-term benefits could be great.