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Vitamin D and COVID-19

Dr Roger Henderson
Reviewed by Dr Roger HendersonReviewed on 13.10.2023 | 5 minutes read

Vitamin D has been hailed as a helper in the fight against COVID-19. Judging by the empty supermarket shelves, the public is listening. But what’s the theory behind it and where’s the evidence? Can vitamin D stop us catching COVID-19? Or stop it from making us really ill? We’ve examined the facts.

Why do scientists think vitamin D fights COVID-19?

Vitamin D strengthens bones and teeth, relieves muscle aches, keeps blood vessels elastic and wards off depression and mental fatigue.

Some think it may also play a role in the immune response to fight off respiratory infections. Coronavirus is one such infection – a particular strain is a virus causing COVID-19 disease.

Vitamin D deficiency is more common in the BAME community, elderly and care home residents, and those with long-term health conditions such as obesity, diabetes and high blood pressure. These groups are also the people most susceptible to catching COVID-19, and the most at risk of serious illness and death.

Where's the evidence?

We can look at this from how people fared if they were vitamin D deficient and caught COVID-19.

A combined review of research papers (a systematic review) found low vitamin D levels in all patients with COVID-19, out of nearly 5,000 people. These patients were more likely to have high blood pressure, cardiovascular disease, chronic kidney disease, diabetes, obesity and respiratory conditions like asthma and COPD. So should we conclude that vitamin D deficiency puts those already vulnerable from their health conditions at even higher risk? Or are these not linked, and those with vitamin D deficiency also happen to be more likely to be unwell from COVID-19?

Another systematic review found that in those with the most severe COVID-19 illness, two out of three had vitamin D deficiency. Those who were deficient were more likely to be admitted to hospital or to die. One conclusion is that vitamin D could protect against more severe disease.

However, a study in Spain found no link between vitamin D deficiency and severity of disease. They did agree that most patients admitted to hospital with COVID-19 had low vitamin D levels.

So what do we make of the conflicting evidence? There is a possible association here that vitamin D deficiency may allow COVID-19 infections in, and/or may make any COVID-19 infection much more severe. However, many factors are at play and these groups are at risk of many health complications, so this needs more research before scientists declare there is a definite link.

What if we start taking vitamin D when we get COVID-19?

This is another way scientists have looked for evidence of a relationship between vitamin D and COVID-19: if you catch COVID-19, will starting vitamin D medication help you on to recovery?

One study from India found those with a positive COVID test but mild disease or without symptoms – they found that swabs turned negative more quickly and other markers of immune system activity had reduced more rapidly with high dose vitamin D supplements.

Another from Brazil found that high dose vitamin D did not help severely ill COVID-19 patients did not prevent the need for ventilators or increase the chance of survival.

Researchers from King’s College London found that vitamin D supplements may reduce the chance of catching COVID-19 by 9%, but that this was only true for women. However, protection from COVID-19 was higher for those taking probiotics (14% reduction), multivitamins (13%) or omega 3 (12%). But could these people be more health-minded, adhering to all the safety measures when out and about to reduce risks, and perhaps less likely to suffer lifestyle-related conditions such as diabetes.

Vitamin D supplements don’t usually cause side effects or problems, and if you’re taking a standard dose regularly (10 micrograms or 400 international units), there is no risk of toxicity, unless you have certain medical conditions such as cancer or severe kidney disease.

There is no strong scientific evidence to show that very high intakes (ie, mega supplements) of vitamin D will be beneficial in preventing or treating COVID-19.

So the verdict is…

Well, it’s tricky. Some studies have seen a really positive gain, but other studies have shown vitamin D levels have little or no effect on COVID-19. It’s also a complex picture in this brand new disease, raising questions about whether those with COVID-19 in the community can be compared to those in hospital, and how we can account for age, gender, weight and other health problems to give a one-size-fits-all verdict.

The UK government says it awaits more research. But in the meantime, it has been recognised that vitamin D deficiency may be a bigger problem than ever, as the pandemic has kept many indoors.

With the relatively low risk of taking supplements, and all of the health benefits of keeping vitamin D levels topped up, the government has offered to send out four months’ supply of supplements free to those in the most vulnerable group. It says that even if this just helps bone and muscle health, it’s worth it.

See if you qualify [HERE.](https: //

The government continues to advise everyone in the UK to take vitamin D supplements from October to April. Those at higher risk of deficiency (those in the BAME community, those indoors a lot, or those who cover themselves when out) should buy supplements all year round.

So the government appears to have hedged their bets, and they call on the public to hedge theirs while everyone waits for more research regarding vitamin D and COVID-19 to be published. It seems like the potential gains are much higher than the risks.

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Dr Roger Henderson
Reviewed by Dr Roger Henderson
Reviewed on 13.10.2023