Vitamin D is known to play a vital role in a range of functions, and is key for keeping our bones, teeth and muscles healthy.

There’s now also growing interest in whether it could help protect against Covid-19.

Scientists from Queen Mary University of London are launching a new trial to investigate whether vitamin D protects against the virus, as there’s already evidence that it might reduce the risk of respiratory infections, with some recent studies suggesting people with lower vitamin D levels may be more susceptible to coronavirus.

“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,” says lead researcher Professor Adrian Martineau.

It’s estimated that roughly one in five people have low vitamin D levels, according to the NHS, which is hardly surprising when we get most of it from sunlight on our skin – hence why vitamin D is often dubbed the ‘sunshine vitamin’.

“Making sure you’re getting enough vitamin D is likely to really benefit your bone and muscle health in the long term,” explains nutrition scientist Bridget Benelam from the British Nutrition Foundation (BNF). “Vitamin D is also involved in supporting our immune system, something we’re all really aware of in light of the coronavirus pandemic. No vitamin can prevent or cure Covid-19, but if you’re not getting enough vitamin D, increasing your intake, alongside a healthy diet, can help keep your immune system working as well as possible.”

And dietitian Dr Carrie Ruxton, from the Health & Food Supplements information Service, notes: “Vitamin D is vital because it contributes to the uptake of calcium by bones and teeth and helps regulate blood levels of calcium and phosphorus.”

So, whatever the outcome of the Covid-19 trial, vitamin D is already known to be crucial for optimal health. Here’s four reasons why it’s important to make sure you get enough vitamin D…

1. Stronger bones
Vitamin D helps regulate the absorption of calcium and phosphorus, so a lack of the vitamin can lead to poor calcification of the skeleton. The BNF explains that prolonged vitamin D deficiency in children leads to rickets, which can cause bone pain, poor growth and bone deformities including bowed legs, curvature of the spine, and thickening of the ankles, wrists and knees, and fractures.

While rickets was for a long time virtually wiped out in the UK, due to fortification of foods and improved diets, in recent years, cases are again being reported. In addition, while osteoporosis in adults isn’t directly caused by vitamin D deficiency, the vitamin can help manage the disease, says the BNF.

2. Stronger muscles
In adults, vitamin D deficiency can lead to osteomalacia, which causes aching bones and muscles plus muscle weakness, which can make standing and walking difficult.

3. Better teeth
Because of its role in regulating the the absorption of calcium, vitamin D also helps keep teeth strong, says the BNF.

4. Improved immunity
A 2019 University of Edinburgh study suggests low levels of vitamin D may lead to an increase in immune responses potentially linked to a raised risk of autoimmune conditions, such as multiple sclerosis.

“There are vitamin D receptors on many immune cells,” says Ruxton, “suggesting that it has a widespread role in optimal immunity – an important point as we face a continuation of the Covid-19 crisis, just when the winter flu and cold season approaches.”