Yesterday was the shortest day for northern hemisphere dwellers. For some people the lack of sunlight at this time of year may be more detrimental than for others. A new study is investigating the impact that Yorkshire’s grey winter skies will have on a bunch of young healthy North American footballers who normally live in sunnier climes.

All of us need vitamin D to maintain strong bones, muscles and a heathy immune system. Our main source of this essential hormone is from ultraviolet B rays in sunlight, which reacts with cholesterol in our skin to make vitamin D. But during the winter months high latitude locations like the UK don’t receive enough sunlight to keep our vitamin D levels topped up.

Owen Kavanagh, from York St John University, and colleagues are monitoring the vitamin D levels of athletes taking part in the i2i International Soccer Academy, to see how they cope with less sunlight than they are used to. “We are expecting that the athletes will have a larger decrease in vitamin D levels than the locals, and that this will result in poorer athletic performance, with more susceptibility to injuries, infections and bad moods,” explains Kavanagh.