Our vitamin D levels will plummet this winter.

Vitamin D is a pro-hormone which our bodies naturally produce by synthesising ultraviolet light from the sun. It is needed for the body to make proper use of calcium for stronger bones and teeth and maintain a healthy immune system.

Ninety per cent of our essential vitamin D must come from our skin’s unprotected exposure to the sun, with only 10 per cent gained through diet. But the UK is currently in its vitamin D winter where winter sunshine is too weak to stimulate production of vitamin D.

When the sun is below 45 degrees in the sky, nearly all of the UVB it produces is absorbed by the atmosphere, rather than our bodies. So in the UK, the angle of our winter sun is simply not strong enough to ensure sufficient vitamin D production at the levels we need.

And even when the strength and angle of the sun is good enough for optimum vitamin D generation in our bodies, our nation’s infamous cloudy weather often blocks it out completely, hindering the absorption of those all important UVB rays. Therefore only a very few people are likely to generate enough vitamin D through natural sunlight exposure alone.

Diseases related to vitamin D deficiency, including multiple sclerosis, Type 2 diabetes, bone diseases such as osteoporosis and a growing number of internal cancers are believed to cost the UK taxpayer £29 billion annually – more than a quarter of the NHS budget.

More commonly, general symptoms associated with vitamin D deficiency include lack of energy and fatigue, headaches, poor immune system, muscle aches and depression.

So get out there and get yourself some supplementation advice. Vitamin D home test kits retail at £25.