Current vitamin D recommendations for children may be inadequate
Most children with vitamin D deficiency who received daily supplements still failed to reach the recommended concentration of 30 ng/mL after 6 months, according to research in The Journal of Clinical Endocrinology & Metabolism.
In a randomized, double blind, placebo-controlled trial of vitamin D in otherwise healthy children from Pennsylvania, researchers also found that the effects of vitamin D supplementation varied by race and that supplementation was more effective and significant only in black children.
Kumaravel Rajakumar, MD, MS, of the department of pediatrics at the University of Pittsburgh, and colleagues analyzed data from 157 healthy children aged 8 to 14 years (84 black, 73 white) who were not receiving vitamin supplements. Researchers enrolled children from October to March of 2008 to 2011 and randomly assigned the participants to 1,000 IU vitamin D daily or a daily placebo for 6 months. Researchers measured BMI, summertime sunlight exposure, melanin indexes and dietary intake of vitamin D and calcium using a food frequency questionnaire at baseline and 6-month follow-up visits. Researchers also measured serum calcium, phosphorus, albumin, 25-hydroxyvitamin D, parathyroid hormone (PTH), osteocalcin and collagen type 1 cross-linked C-telopeptide (CTx) concentrations at baseline, 2 months and 6 months.
Researchers found that vitamin D concentrations were higher in children receiving supplementation at both the 2- and 6-month follow-up visits compared with the placebo group at 2-month follow-up (26.4 ng/mL vs. 18.9 ng/mL; P < .0001) and at 6-month follow-up (26.7 ng/mL vs. 22.4 ng/mL; P < .003), although concentrations mostly remained less than 30 ng/mL. Of the supplemented children with baseline 25-(OH)D concentrations less than 20 ng/mL, only 14% reached concentrations 30 ng/mL or greater, according to researchers.
“These findings suggest that currently recommended daily dietary allowances of vitamin D of 600 IU may be inadequate for preventing vitamin D deficiency in children,” the researchers wrote.
In addition, black children in the vitamin D arm had higher 25-(OH)D concentrations compared with white children at the 2-month follow-up, but not at the 6-month follow-up.
“Our observations affirm the previously observed association between baseline 25-(OH)D concentration and the changes that occur in response to vitamin D supplementation,” the researchers wrote. “There was a greater 2-month increase in 25-(OH)D concentration with vitamin D supplementation and a strong negative association between change in 25-(OH)D concentration and baseline 25-(OH)D concentration in black children compared with white children.”
Researchers also found that vitamin D supplementation had no measurable effect on bone turnover markers or PTH.
“The association between 25-(OH)D and PTH concentrations was inverse and linear without evidence of a plateau,” the researchers wrote. “Overall, vitamin D supplementation had no effect on PTH and bone turnover.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.