Children with stunted growth do not experience improved growth or a reduction in rickets risk by taking vitamin D supplements, a clinical trial suggests. Researchers randomly assigned 3,046 children in Kabul, Afghanistan, ranging in age from 1 to 11 months to receive either placebo or oral vitamin D (100,000 IU) every three months for 18 months. At baseline 12% of the babies were underweight, while stunting was identified in 13% of babies and wasting was identified in 7% in both the vitamin D and the placebo groups. By the end of the trial, researchers found no statistically significant differences between the two groups in weight-for-height or weight-for-age Z scores. Nor were there differences in the prevalence of rickets in the placebo (5.5%) and vitamin D (5.3%) groups. "This is surprising," said lead study author Francesca Crowe of the University of Birmingham in the UK. "Previous studies suggested that vitamin D deficiency would be high among children in inner-city Kabul but their blood levels of vitamin D were not as low as anticipated and the rates of rickets was also low," Crowe said by email. Researchers did find mean serum 25-hydroxyvitamin D was higher in the vitamin D supplementation group than the placebo group after the first dose of vitamin D supplementation (115 vs 39 nmol/L). But there wasn't a significant difference in vitamin D levels between the two groups after the final blood test done more than four months after the final dose of vitamin D or placebo. In subgroup analysis, children with more than 300 mg/day of dietary calcium had slightly better height-for-age Z scores at the end of the study, but the test for interaction by calcium intake wasn't statistically significant. It's possible that impaired growth, as demonstrated by the high prevalence of stunting in the study group, may have contributed to the low rate of rickets irrespective of vitamin D levels, the researchers write in Pediatrics. One limitation of the study is that researchers lacked data on the volume and nutritional composition of any breast milk fed to babies in the study, researchers note. In addition, the primary endpoint of the trial was to assess the impact of vitamin D supplementation on the incidence and severity of pneumonia. The effect of vitamin D supplementation on rickets and linear growth were secondary objectives of the trial. In this study population, it's possible that babies already had vitamin D and calcium intake that were sufficient to prevent rickets, said Dr. Steven Abrams, a professor of pediatrics at Dell Medical School at the University of Texas at Austin. "Certainly, in populations with low vitamin D status this is important therapy, but it has limits including the need to make sure the diet has enough calcium as well as giving the vitamin D," Dr. Abrams, who wasn't involved in the study, said by email. "Those with significant stunting should have a dietary assessment including calcium intake done and likely would benefit from assessment of vitamin D status before intervention," Dr. Abrams advised. —Lisa Rapaport Source
