People who suffer the most severe symptoms from Covid are almost twice as likely to be deficient in vitamin D, according to a new study.
Health Secretary Matt Hancock has now ordered a review into the use of vitamin D in helping to protect against coronavirus, despite previously saying it did not appear to have any effect.
However, a recent study of 216 Spanish patients is the latest to suggest that low levels of the vitamin is linked to serious cases of the virus.
But how can you get more vitamin D into your diet and why is it important?
What does vitamin D do?
Vitamin D is often referred to as the sunshine vitamin because the body creates the vitamin from direct sunlight on the skin when outdoors.
From between late March to the end of September, most people should be able to get all of the vitamin D they need from sunlight, but in the colder months, many don’t get the required levels.
The vitamin plays a vital role in a range of functions, helping to maintain calcium and phosphate levels, which help to keep bones, teeth and muscles healthy.
Official guidance urges adults and children over the age of four to consider taking a daily supplement containing 10 micrograms of vitamin D to keep their levels up during the autumn and winter.
How can I boost my vitamin D levels?
Between October and early March, people in the UK don’t get enough vitamin D from sunlight alone, but there are other ways you can boost your intake.
The NHS recommends eating foods which are rich in the vitamin, including oily fish, red meat and fortified food, such as some fat spreads and breakfast cereals.
The following foods all contain high levels of vitamin D and consuming more of these in the winter months will help to get your intake levels up.
As well as being rich in protein and omega-3 fatty acids, salmon also contains high levels of vitamin D.
While egg whites contain most of the protein in an egg, the fat, vitamins and minerals are mostly found in the yolk.
One egg yolk will provide around 10 per cent of your daily dose of vitamin D, and it’s also rich in zinc and selenium.
Canned tuna is packed with vitamin D and it is a lot cheaper than buying fresh fish.
There are plenty of popular lunchtime staples to choose from to ensure you get your daily dose, from a tuna sandwich or salad, to baked potato topped with tuna and sweetcorn.
Mushrooms don’t naturally provide a high level of vitamin D, but some are treated with UV light, meaning they offer a much larger dose of the nutrient than normal.
Wild mushrooms are also a great source of vitamin D2, which helps to raise blood levels of vitamin D.
Cow’s milk is naturally a good source of nutrients, including calcium, phosphorus and riboflavin, but in several countries it is fortified with vitamin D.
As vitamin D is mostly found in animal products, some plant-based milk substitutes, including soy and almond milk, are also often fortified with this nutrient.
Another good way of introducing more vitamin D into your diet is by taking daily dietary supplements.
These can be found in most supermarkets, pharmacies or health food shops.
How does vitamin D affect Covid symptoms?
Several scientific studies have suggested that vitamin D can help to protect against coronavirus.
In a recent Spanish study of 216 Covid patients, 82 per cent were found to be deficient in vitamin D. By comparison, among a population without coronavirus, only 47 per cent were found to have a vitamin D deficiency.
A separate paper, published in BMJ Nutrition, Prevention and Health, published on Tuesday (27 October) found that people who took vitamin D supplements were less likely to suffer respiratory problems in general.
Elsewhere, researchers at Queen Mary University are running a project to determine whether correcting vitamin D deficiencies over the winter can reduce the risk and/or severity of coronavirus and other acute respiratory infections.
Lead researcher Professor Adrian Martineau, of Queen Mary University of London, said: “There is mounting evidence that vitamin D might reduce the risk of respiratory infections, with some recent studies suggesting that people with lower vitamin D levels may be more susceptible to coronavirus.
“Many people in the UK have low vitamin D levels, particularly in the winter and spring, when respiratory infections are most common.
“Vitamin D deficiency is more common in older people, in people who are overweight, and in black and Asian people – all of the groups who are at increased risk of becoming very ill with Covid-19.”