Findings suggest that vitamin D deficiency could place millions of children at risk for high blood pressure and other risk factors for heart disease. The study is published in the online version of Pediatrics.
Vitamin D deficiency was thought to be relatively rare in the U.S. However, recent studies have documented this growing problem in adults. With cases of rickets (a bone disease in infants caused by low vitamin D levels) on the rise, it became clear that many children were also not getting enough of this essential vitamin, which is needed for healthy bone growth, among other biological processes.
“Several small studies had found a high prevalence of vitamin D deficiency in specific populations of children, but no one had examined this issue nationwide,” said study leader Michal Melamed, MD, assistant professor of medicine and of epidemiology and population health at Einstein.
To learn more about the prevalence of vitamin D deficiency (defined as less than 15 ng/mL of blood) and vitamin D insufficiency (15 to 29 ng/mL), the researchers analyzed data on more than 6000 children, ages one to 21, collected by the National Health and Nutrition Examination Survey (NHANES) 2001-2004.
The researchers found that 9% of the study sample, equivalent to 7.6 million children across the U.S., was vitamin D deficient, while another 61%, or 50.8 million, was vitamin D insufficient. Low vitamin D levels were especially common in children who were older, female, African-American, Mexican-American, obese, drank milk less than once a week, or spent more than four hours a day watching TV, playing videogames, or using computers.
The researchers also found that low levels of vitamin D deficiency were associated with higher parathyroid hormone levels, a marker of bone health, higher systolic blood pressure, and lower serum calcium and HDL cholesterol levels, which are key risk factors for heart disease.
“We expected the prevalence of vitamin D deficiency would be high, but the magnitude of the problem nationwide was shocking,” said lead author Juhi Kumar, MD, MPH, a fellow in pediatrics at Children’s Hospital at Montefiore Medical Center, The University Hospital and Academic Medical Center for Albert Einstein College of Medicine.
In the study, children who took vitamin D supplements (400 IU/day) were less likely to be deficient in the vitamin. However, only 4% of the study population actually used supplements. The American Academy of Pediatrics, which recently updated its vitamin D guidelines, now recommends that infants, children, and teens should take 400 IU per day in supplement form.
The authors recommend that pediatricians should routinely screen high-risk children for vitamin D deficiency, and that parents should ensure that their kids get adequate amounts of the vitamin through a combination of diet, supplements and exposure to sunlight.