Video and words by ITV video producer Natalia Jorquera
Sales of vitamins that claim to boost your immune system are up, but can certain supplements help guard against Covid-19?
Well, there is growing interest around vitamin D.
It's nicknamed the sunshine supplement, because the main way we get it is from direct sunlight on the skin.
It has primarily been thought to be important for bones and muscles, but studies have shown that taking regular doses of vitamin D can help boost defences against infections like influenza.
So can vitamin D protect against coronavirus?
The current evidence is conflicting, but that's because the data has only come from small studies.
Some research has found that patients with a vitamin D deficiency are more likely to test positive for the virus.
Research has also found that good levels of vitamin D have been associated with a less severe Covid illness and a better survival rate.
However, other clinical research studies couldn't find a cause and effect link between vitamin D levels and getting Covid-19.
At the moment it's not clear whether vitamin D deficiency is causing or reflecting individuals’ increased susceptibility to Covid-19, more research is needed.
But scientists are all agreed that being deficient in vitamin isn't a good thing.
Sabyasachi Sen, a professor of endocrinology and medicine at George Washington University told ITV News: "Low vitamin D has been associated with increased, conditions of obesity, metabolic syndrome and so on and so forth. You definitely don't want to be deficient in it.
"I wouldn't say that it goes and prevents Covid, but it might help your generalised immune system to not make you more predisposed to the disease."
When asked if you should take a vitamin D supplement Adrian Martineau a respiratory physician at Queen Mary University of London said: "We already do know that taking a low dose of vitamin D is good for your muscles and bones.
"The government recommends that, especially during this time of year, winter and spring, when sunshine isn't strong enough to make vitamin D in our skin, we all take a supplement of 10 micrograms, 400 units of vitamin D per day to protect muscles and bones.
"Now, I think there's a fighting chance this might also help against Covid."
It has been reported that one in four Brits are deficient in vitamin D, particularly those from black and ethnic minorities – who have higher levels of melanin in the skin, which tends to reduce the creation of vitamin D from sunlight – and are a group who have been disproportionately affected by the virus.
It's this link that led Labour MP Rupa Huq to form an unlikely union with former Brexit Secretary David Davis to campaign for the government to review evidence into the benefits of vitamin D and consider a free supplement scheme to combat vitamin D deficiencies.
And after a few meetings presenting evidence to Health Secretary Matt Hancock, who initially disregarded any link between vitamin D and Covid-19, at the end of November 2020 the government announced it would offer four months of free vitamin D supplements to all those in care homes and those shielding.
Ms Huq said: "It's a massive step forward that the government is going to be prescribing four month's free vitamin D supply to the most vulnerable, but the thing is, people need to know about it and I think it's hidden away on a gov.uk website that then takes you to an NHS website and it's all conflicting information." Those who are most at risk from Covid have until February 21 to apply for the free supplements by visiting nhs.uk.
The current NHS guidance for adults and children is to take 10 micrograms of vitamin D a day between October and March, but as lockdowns have reduced people's exposure to the sun they say it's more important for people to take the supplements.
Although the NHS does stress there is currently not enough evidence to support taking vitamin D to prevent or treat coronavirus.
More large studies are needed. Mr Martineau and his team are currently conducting a clinical trial looking at whether different doses of vitamin D might reduce the risk of getting Covid or reduce the severity of Covid, but he doesn't think you need to wait for his results before you start taking the supplement.He said: "Take 10 micrograms or 400 units of vitamin D every day. We know this will benefit your bones and muscles, and there's a fighting chance that it could reduce your risk of COVID too, although that has not yet been proven."