California [US], December 9 : Vitamin D supplements do not strengthen bones or protect children with vitamin D deficiency from fractures, according to a large clinical trial undertaken by the Harvard T.H. Chan School of Public Health and Queen Mary University of London.
The results refute commonly accepted beliefs about how vitamin D affects bone health.
Before they become 18, over one-third of kids will suffer at least one fracture. This is a major global health issue, as childhood fractures can lead to life years of disability and/or poor quality of life. Because vitamin D helps to promote bone mineralization, there has been an increasing amount of interest in the possibility that taking supplements of the vitamin could strengthen bones.
However, there have never before been any clinical studies done to see if vitamin D supplementation can shield kids from bone fractures.
In order to ascertain whether vitamin D supplementation would reduce the risk of bone fractures or increase bone strength in schoolchildren, researchers from Queen Mary and Harvard collaborated with partners in Mongolia, a country with a particularly high fracture burden and a high prevalence of vitamin D deficiency. Published in Lancet Diabetes & Endocrinology today, December 1, the study represents the largest randomised controlled trial on vitamin D supplementation in children to date.
Over the course of three years, 8,851 schoolchildren aged 6-13 living in Mongolia received a weekly oral dose of vitamin D supplementation. 95.5 per cent of participants had vitamin D deficiency at baseline, and study supplements were highly effective in boosting vitamin D levels into the normal range.
However, they had no effect on fracture risk or bone strength, measured in a subset of 1,438 participants using quantitative ultrasound.
The trial findings are likely to prompt scientists, doctors and public health specialists to re-consider the effects of vitamin D supplements on bone health.
Dr Ganmaa Davaasambuu, Associate Professor at the Harvard T.H. Chan School of Public Health, said, "The absence of any effect of sustained, generous vitamin D supplementation on fracture risk or bone strength in vitamin D deficient children is striking. In adults, vitamin D supplementation works best for fracture prevention when calcium is given at the same time - so the fact that we did not offer calcium alongside vitamin D to trial participants may explain the null findings from this study."
Professor Adrian Martineau, Lead of the Centre for Immunobiology at Queen Mary University of London, added, "It is also important to note that children who were found to have rickets during screening for the trial were excluded from participation, as it would not have been ethical to offer them placebo (dummy medication). Thus, our findings only have relevance for children with low vitamin D status who have not developed bone complications. The importance of adequate vitamin D intake for prevention of rickets should not be ignored, and UK government guidance recommending a daily intake of 400 IU vitamin D remains important and should still be followed."
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