Daily Junction.mobi portalHealth · November 25, 2024 · Dr. Nadia Okoro · 5 min
Vitamin D keeps bones, teeth and muscles healthy, and many people in the UK run low in winter. Here are the signs of deficiency, where vitamin D comes from, and the NHS advice on supplements.
Vitamin D is unusual among nutrients: we get most of it not from food but from sunlight on our skin. That works well in a sunny climate — and rather less well in the UK, where for half the year the sun is simply too weak to do the job. As a result, low vitamin D is one of the most common nutritional gaps in Britain, particularly over winter. Here is what it does, how to spot a shortfall, and what the NHS advises. This is general information, not medical advice; speak to your GP or pharmacist if you are concerned about your levels.
Vitamin D deficiency is a state of having too little vitamin D in the body to keep bones, teeth and muscles healthy. Vitamin D's main job is to help the body absorb calcium and phosphate from the diet — minerals that are essential for strong bones and teeth and for normal muscle function. Without enough vitamin D, the body cannot use those minerals properly, however much you consume.
It is sometimes called the "sunshine vitamin," because the main source is not food at all.
There are three routes, and their relative importance is the key to understanding why deficiency is so common in the UK.
Most people get the majority of their vitamin D from sunlight. When skin is exposed to summer sunlight, it makes vitamin D from a type of cholesterol. The catch is that this only happens when the sun is strong enough. In the UK, from about late March to the end of September the sun can do the job; from October to March the sunlight is too weak, so the skin makes little or no vitamin D. Over those months, the body draws on stores built up in summer — which is why levels so often dip by late winter.
Few foods naturally contain much vitamin D, which is why diet alone rarely meets needs. The main dietary sources are:
Building these into a varied diet helps, and oily fish in particular fits well within a balanced plate. But for most people, food alone does not supply enough over winter.
Because sunlight is seasonal and food sources are limited, supplements are the reliable way to top up, especially in the darker months — which is exactly why the NHS makes the recommendation below.
Mild vitamin D deficiency frequently causes no obvious symptoms at all, which is part of why it goes unnoticed. When symptoms do appear, they can be vague and easy to attribute to other things:
In children, severe, prolonged deficiency can cause rickets, where bones become soft and deformed. In adults, it can cause osteomalacia, a softening of the bones leading to pain and weakness. These are the serious end of the spectrum and are far less common than mild, symptomless deficiency.
Because the early signs overlap with so many other things — including the everyday tiredness behind an afternoon energy slump or poor sleep — symptoms alone cannot confirm deficiency. A blood test, arranged through your GP, is the only way to know for sure.
Some people are more likely to run low and may need to be especially careful:
The official UK guidance is clear and worth knowing:
Crucially, more is not better. Taking too much vitamin D over a long period can cause too much calcium to build up in the body, which can harm the bones, heart and kidneys. For most adults and children over 11, the NHS advises not taking more than 100 micrograms a day unless told to by a clinician. If in doubt, a pharmacist can advise on suitable products and doses.
Putting it together, a sensible approach for most people is to:
Looking after vitamin D sits within the bigger picture of general wellbeing — alongside good sleep, regular activity and balanced eating — rather than being a single fix on its own.
Vitamin D keeps bones, teeth and muscles healthy by helping the body absorb calcium, and most of it is made in the skin from summer sunlight. In the UK that means levels commonly fall between October and March, when the sun is too weak — so deficiency, often symptomless but sometimes causing tiredness and aches, is widespread. Oily fish and fortified foods help, but the NHS advises everyone consider a daily 10 microgram supplement in autumn and winter, and some groups all year. Just don't overdo it: too much can be harmful, and a blood test through your GP is the way to confirm a genuine shortfall.
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