More than 2.5 million vulnerable people in England will be offered free vitamin D supplements for the winter, the government has announced.
All care homes will receive a provision for their residents, while individuals deemed clinically extremely vulnerable will receive a letter inviting them to opt into the scheme.
The vitamin will be deliver to their homes free of charge, starting in January, and will provide four months' supply of supplements to last people through the winter.
Vitamin D is linked to boosting bone and muscle health and can be naturally absorbed through the skin through sunlight.
The advice from Public Health England is for everybody to take 10 micrograms (400 IU) of vitamin D a day between October and early March to keep bones and muscles healthy.
Limited daylight hours in the winter and wearing of layers make it difficult to take in enough sunlight during the winter, making vitamin D intake particularly important when people are having to stay indoors due to coronavirus restrictions.
While there is no strong evidence that vitamin D can protect against Covid-19, the vitamin is known to have general health benefits.
Health Secretary Matt Hancock has ordered a re-review to examine the link between Covid-19 and vitamin D, with the findings set to be published towards the end of the year.
Mr Hancock said: "Because of the incredible sacrifices made by the British people to control the virus, many of us have spent more time indoors this year and could be deficient in vitamin D.
"The government is taking action to ensure vulnerable individuals can access a free supply to last them through the darker winter months. This will support their general health, keep their bones and muscles healthy and crucially reduce the pressure on our NHS.
A number of studies indicate vitamin D might have a positive impact in protecting against Covid-19
"A number of studies indicate vitamin D might have a positive impact in protecting against Covid-19. I have asked NICE and PHE to re-review the existing evidence on the link between Covid-19 and vitamin D to ensure we explore every potential opportunity to beat this virus." Dr Alison Tedstone, Chief Nutritionist at Public Health England, said: "Vitamin D is important for our bone and muscle health.
"We advise that everyone, particularly the elderly, those who don’t get outside and those with dark skin, takes a vitamin D supplement containing 10 micrograms (400IU) every day.
"This year, the advice is more important than ever with more people spending more time inside, which is why the government will be helping the clinically extremely vulnerable to get vitamin D."