There's a scientific reason why exercising in the winter can be tough

The clocks have gone back and the nights are growing darker, meaning a night spent on the sofa is far more appealing than bracing the cold in our gym kit.

But it turns out, there’s also a scientific reason behind our urge to hibernate come winter, and it’s all to do with our vitamin D levels.

A new study published in the European Journal of Preventative Cardiology discovered a correlation between higher vitamin D levels and increased cardiorespiratory fitness (the ability of the heart and lungs to supply oxygen to the muscles during exercise).

On the flip side, because sunlight – our go-to vitamin D source – is more scarce in winter, our levels of the vitamin go down – along with our fitness levels.

The study assessed health data belonging to 1,995 people between the ages of 20 and 49. The research team then analysed each participant’s oxygen consumption level alongside their vitamin D levels.

Researchers discovered that participants with the highest amount of vitamin D levels had a significantly higher cardiorespiratory fitness than participants in the lowest category.

One of the authors of the study Dr Amr Marawan concluded, “Our study shows that higher levels of vitamin D are associated with better exercise capacity.”

So, that explains why our fitness levels often drop off in winter – because we are lacking the nutrient we need to supply oxygen to our muscles.

How can fitness fanatics ensure that they’re getting the right amount of vitamin D during the winter?

According to the NHS, we can add vitamin D into our daily diet through oily fish such as salmon, mackerel, herring and sardines alongside red meat and eggs.

Vitamin D supplements may also be used as part of a balanced diet though Dr Marawan warns of the dangers of toxicity in the study.

“It is not the case that the more vitamin D, the better,” adds Dr Marawan. “Toxicity is caused by megadoses of supplements rather than diet or sun exposure so caution is needed when taking tablets.”

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