Despite previous assumptions, taking vitamin D doesn't help children avoid fracturing their bones.
Even if the child has a vitamin D deficiency, the supplements do not increase bone strength or prevent bone fractures, according to new research in the journal Lancet Diabetes & Endocrinology.
These findings go against the grain of widely held perceptions of how vitamin D helps bone health, the authors say in the paper. Vitamin D promotes the mineralization of bone, leading to the common belief that it can prevent bone fractures. However, until now, this had not been clinically tested. Childhood fractures can lead to disability and poor life quality, with around one-third of children having at least one fracture before they turn 18.
A child holds up an X-ray photograph. Research has found that vitamin D supplements do not prevent bone fractures.A child holds up an X-ray photograph. Research has found that vitamin D supplements do not prevent bone fractures.ISTOCK / GETTY IMAGES PLUS"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 ('mineralization')," Adrian Martineau, study co-author and professor of respiratory infection and immunity at Queen Mary University of London, told Newsweek.
"Additionally, some observational studies have reported a link (association) between low vitamin D levels and increased risk of bone fracture in children. So there was a possibility that vitamin D supplements might have a role in reducing fracture risk in children who had low baseline levels to start with.
"However, clinical trials of vitamin D supplements were need to test whether the link between low vitamin D status and reduced fracture risk was causal. These hadn't been done previously."
The authors tested whether taking vitamin D would decrease the risk of fractures in schoolchildren in Mongolia, where children often have bone fractures. They dosed 8,851 schoolchildren aged 6 to 13 with vitamin D every week for three years, 95.5 percent of whom had a vitamin D deficiency.
After the trial, the children were found to have normal vitamin D levels, but had no change in their fracture risk, and no increased bone strength as tested using ultrasound. This marks the largest randomized controlled trial of vitamin D supplementation ever conducted in children.
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The authors said that children with rickets were excluded as giving them placebo medication would have been cruel. Therefore, these findings are relevant only for those without rickets. The disease is a softening and weakening of bones caused by an extreme and prolonged vitamin D deficiency in children.
"Exposure to sunshine stimulates synthesis of vitamin D in the skin—and Mongolian winters are long and cold, so children aren't exposed to sunshine of sufficient intensity to stimulate the vitamin D they need for long periods of the year," Martineau said.
"In big cities like Ulaanbaatar, air pollution may reduce intensity of ultraviolet B reaching residents. Diets may not be rich in oily fish, which is the main dietary source of vitamin D (unlike other vitamins, vitamin D is only available in relatively few foods). Vitamin D deficiency is also common in other countries including India, Pakistan, Bangladesh and Saudi Arabia."
This study shows that in Mongolia vitamin D deficiency does not cause childhood fractures. The authors note that preventing accidents is a key way to minimise bone fractures in children.
"Accident prevention is a major focus, as are measures to reduce traumatic impact of accidents (e.g. wearing helmets and protective pads/clothing while doing sports such as cycling, skating, skateboarding, and use of impact-absorbing surfaces in school playgrounds)," Ganmaa Davaasambuu, an associate professor of medicine and nutrition at Harvard T.H. Chan School of Public Health, told Newsweek.
"Healthy lifestyle factors include exercising, running, jogging, and enjoying sunshine where and when you can improve bone strength and mineral content and decrease falls and fractures.
"Eating a healthy diet, more specifically green leafy vegetables and fermented food such as natto, improves your gut microbiome, vitamin-K-producing bacteria in the gut, and increases the synthesis of vitamin K2, which in turn guides calcium toward your bones rather than kidneys and arteries, where an excess of calcium could pose issues."
Do you have a tip on a science story that Newsweek should be covering? Do you have a question about vitamin D? Let us know via science@newsweek.com.Update 12/5/2023 12:03 ET: This article was updated with comment from Martineau and Davaasambuu.
