Vitamin D supplement does not lower fracture risk among children with 25-(OH)D deficiency
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Key takeaways:
- Children receiving a once-weekly vitamin D supplement had a similar number of fractures over 3 years as those receiving placebo.
- The vitamin D group had higher levels of 25-(OH)D and PTH than the placebo group.
A once-weekly oral vitamin D supplementation did not reduce fracture risk over a 3-year follow-up among a group of children with vitamin D deficiency in Mongolia, according to findings published in The Lancet Diabetes & Endocrinology.
“Giving vitamin D supplements without calcium doesn’t reduce fracture risk in schoolchildren, even if they are vitamin D deficient to start with,” Davaasambuu Ganmaa, MD, PhD, associate professor of medicine at Harvard Medical School and Brigham and Women’s Hospital, and Adrian Martineau MD, PhD, professor of respiratory infection at Queen Mary University of London, told Healio. “However, we examined only a single dose of vitamin D given at weekly intervals; therefore, our results do not rule out the potential effectiveness of daily dosing, and/or different dosing of vitamin D supplements.”
Ganmaa, Martineau and colleagues conducted a randomized, double-blind, placebo-controlled trial enrolling 8,851 children aged 6 to 13 years attending 18 public schools in Mongolia. Children were eligible to participate if they had vitamin D deficiency as indicated from a negative QuantiFERON-TB Gold In-tube assay result. Participants were randomly assigned to a soft gel capsule containing 14,000 IU of vitamin D (n = 4,418) or placebo (n = 4,433) once-weekly for 3 years or until the end of the intervention in May 2019. Participant characteristics and demographics were reported by parents at baseline. Serum blood samples were collected at baseline and a subset of 1,465 participants had speed of sound measured at the distal one-third of the radius. At 2 and 3 years, fractures were self-reported by children using a questionnaire. Repeat speed of sound measurements were taken at 1, 2 and 3 years. Follow-up blood samples were collected at 3 years.
No difference in fracture incidence
Of the participants, 4,176 in the vitamin D group and 4,172 in the placebo group completed at least one follow-up fracture questionnaire and were included in the analysis (median age, 9.2 years; 49.4% girls). Of the participants, 95.5% had a serum 25-hydroxyvitamin D level of less than 50 nmol/L at baseline and 31.9% had a serum 25-(OH)D level of less than 25 nmol/L.
There were 677 fractures reported by 521 participants. Fractures occurred in 6.4% of the vitamin D group and 6.1% of the placebo group. Vitamin D supplementation was not associated with a change in fracture risk. No difference in radial speed of sound z score was observed between the vitamin D and placebo groups.
“We found the lack of a protective effect surprising,” Ganmaa and Martineau said. “It has long been known that vitamin D is important in supporting absorption of calcium in the diet, and deposition of calcium in the bones. Additionally, some observational studies have reported a link between low vitamin D levels and increased risk of bone fracture in children. So our expectation was that vitamin D supplements might have a role in reducing fracture risk in children who had very low baseline levels to start with.”
More research needed
At 3 years, the vitamin D group had a higher serum 25-(OH)D level than placebo (72.1 nmol/L vs. 26.1 nmol/L; P < .0001). A lower parathyroid hormone (PTH) level was observed among the vitamin D group vs. the placebo group (4 pmol/L vs. 5.4 pmol/L; P = .0075). No differences were found between the groups in other biochemical measures.
Adverse events were similar between the two groups and no adverse events were determined to have been caused by study preparation.
Ganmaa and Martineau said future research should explore whether giving calcium supplements along with vitamin D supplements may lower fracture risk for children, as many of the participants in the study also had low calcium level in addition to vitamin D deficiency. Additionally, the researchers noted that children with rickets were ineligible for the study, which excluded those with the lowest vitamin D and calcium levels.
“It would be very interesting to investigate further the effect of vitamin D on a few parameters such as PTH, phosphate and alkaline phosphate parsed by dietary calcium intake in this population with very low baseline vitamin D status,” Ganmaa and Martineau said.
For more information:
Davaasambuu Ganmaa, MD, PhD, can be reached at gdavaasa@hsph.harvard.edu.
Adrian Martineau MD, PhD, can be reached at a.martineau@qmul.ac.uk.
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