Getting out into the sunshine is good for your bones, helping your body to produce vitamin D. But Britain is becoming more cloudy in the summer, and it could be having an impact on children’s bone health.
A new Canadian study compared Britain’s cloud cover against the incidence of rickets, which is caused by lack of vitamin D. Cases had been declining since the 1960s but almost doubled between 1997 and 2011, going from 0.56 cases per 100,000 British children to 1.01.
The researchers focused on Britain because it has the longest record of rickets, extending back to the 1960s.
The dramatic increase in rickets has puzzled public health experts, the University of Toronto said. Possible explanations that have been put forward include changing immigration patterns, as people with darker skin absorb less vitamin D from the sun. Other experts are looking at shifting diets or changes in hospital admission policies. But Haris Majeed, a Master’s student in Medical Imaging at the University of Toronto’s Faculty of Medicine, wondered if long-term climate variability in sea surface temperatures played a role.
For the study, he worked with his former thesis supervisor in the Department of Physics, Professor G.W.K. Moore.
“Sea surface temperatures are getting warmer over the North Atlantic, and are known to fluctuate every 60 to 80 years,” Majeed explained. “After the mid-1990s, North Atlantic sea surface temperatures entered a warm phase, decreasing average summer atmospheric pressures and causing more rain, and less sunshine, in the UK.”
Health experts in the UK say that six hours of sunshine a month is needed to produce enough vitamin D in people’s skin. But since the mid-1990s, increasing cloud cover has meant that we get about four hours less sunshine per month in the summer.
“Perhaps if we’re able to understand this condition based on long-term climate variability, we can as scientists save at least a few children from becoming disabled,” Majeed said.
The findings of the research have been published in the Nature journal Scientific Reports.