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We Need to Put Vitamin D Back in Children and Adolescents

Many U.S. children and adolescents have low vitamin D levels, and such levels are associated with adverse physiologic processes.

Small-scale studies have documented low vitamin D levels in children and adolescents, even as evidence mounts about the role of this vitamin in maintaining health and preventing disease. Three studies further our understanding of vitamin D status in children.

One study was based on data from 6275 children and adolescents who participated in the 2001–2004 National Health and Nutrition Examination Survey (NHANES). Overall, 9% of respondents (representing 7.6 million children and adolescents) were vitamin D deficient (serum 25 hydroxyvitamin D [25(OH)D] <15 ng/mL), and 61% (representing 50.8 million) were vitamin D insufficient (serum 25[OH]D, 15–29 ng/mL). Only 4% of participants reported taking 400 IU of vitamin D daily during the past 30 days. Among those aged 13–21 years, vitamin D deficiency was detected in 3% and 5% of white boys and girls, 43% and 59% of non-Hispanic black boys and girls, and 7% and 20% of Mexican American boys and girls. Deficiency rates were generally lower in children aged 7–12 years and lowest in children aged 1–6 years. Risk factors associated with deficiency were obesity (odds ratio, 1.9), drinking milk less than once per week (OR, 2.9), and television /video/computer use for more than 4 hours per day (OR, 1.6). Reported use of daily vitamin D supplements reduced the risk for deficiency (OR, 0.4). Compared with participants with vitamin D levels 30 ng/mL, those with deficiency had higher parathyroid hormone (PTH) levels and systolic blood pressure (BP) and lower HDL and serum calcium levels.

Other investigators used the same dataset to examine the effects of low serum 25(OH)D levels in 3577 fasting adolescents (age range, 12–19 years). In analyses that were adjusted for sociodemographic factors and physical activity, 25(OH)D levels were inversely associated with systolic BP and plasma glucose concentrations. Compared with children with vitamin D levels in the highest quartile (>26 ng/mL), those with levels in the lowest quartile (<15 ng/mL) had adjusted ORs of 2.36 for hypertension, 2.54 for fasting hyperglycemia (glucose 100 mg/dL), and 3.88 for metabolic syndrome.

In the third study, investigators examined the relation between serum 25(OH)D levels and insulin and glucose dynamics in 51 black adolescents (mean body-mass index, 43.3 kg/m²) at a hospital-based weight-management clinic. After controlling for BMI and PTH levels, the investigators found no metabolic differences between children with 25(OH)D levels <20 ng/mL and those with levels >20 ng/mL. However, insulin sensitivity was significantly lower and insulin resistance was higher among those with 25(OH)D levels <15 ng/mL compared with those with levels 15 ng/mL.

Comment: Not until 2008 did the American Academy of Pediatrics recommend at least 400 IU of vitamin D daily for children and adolescents, so the prevalence of deficiency and insufficiency might have declined since the 2004 NHANES studies. Nonetheless, many children and adolescents today likely have suboptimal vitamin D levels. Therefore, emphasizing adequate intake of dairy products and supplements at well-child visits is important. The association between low vitamin D levels and television/video/computer use could reflect reduced sun exposure or overweight status (vitamin D is sequestered in fat cells). Since the relation between low vitamin D levels and myriad adverse physiologic processes also has been observed in adults (JW Gen Med Jul 23 2008), the questions arise as to whether low vitamin D levels predispose children to adult morbidities such as hypertension, type 2 diabetes, and atherosclerosis, and whether normalizing vitamin D levels can reduce these risks. The lower levels among minority youth can only exacerbate (and might to some extent explain) racial and ethnic disparities in child and adolescent health status. Maybe measurement of serum 25(OH)D levels should be part of the evaluation for conditions such as hypertension and type 2 diabetes?

— Alain Joffe, MD, MPH, FAAP

Published in Journal Watch Pediatrics and Adolescent Medicine November 4, 2009

Citation(s):

Kumar J et al. Prevalence and associations of 25-hydroxyvitamin D deficiency in US children: NHANES 2001–2004. Pediatrics 2009 Sep; 124:e362. (http://dx.doi.org/10.1542/peds.2009-0051)

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Reis JP et al. Vitamin D status and cardiometabolic risk factors in the United States adolescent population. Pediatrics 2009 Sep; 124:e371. (http://dx.doi.org/10.1542/peds.2009-0213)

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Ashraf A et al. Threshold for effects of vitamin D deficiency on glucose metabolism in obese female African-American adolescents. J Clin Endocrinol Metab 2009 Sep; 94:3200.

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