You may have recently come across headlines implying a connection between vitamin D levels and covid-19. Depending on your preferred news source, these varied in truth.

There were misleading claims those with a severe vitamin D deficiency were twice as likely to die from covid-19 (er, not exactly) to the more balanced suggestion we would all benefit from taking a daily supplement (probably true if you live anywhere north of Rome).

As always, the truth lies somewhere in the middle.

On 7 May, the results of a study were published, analysing hospital records from ten countries affected by covid-19. The research team from Northwestern University looked at data from China, France, Germany, Italy, Iran, South Korea, Spain, Switzerland, the UK and the US.

The data revealed a correlation between countries with overall high mortality rates, such as Italy, Spain and the UK, and low average vitamin D levels compared with countries with lower mortality rates.

The team emphasises these results don’t mean everyone should stockpile vitamin D supplements – the correlation doesn’t automatically imply causation.

vitamin D and covid-19 death rate
Photo by Michele Blackwell on Unsplash

Vitamin D and its role in covid-19 deaths

Vadim Backman, professor of Biomedical Engineering at Northwestern’s McCormick School, led the research. He said the findings shed light on the mechanism by which covid-19 kills its victims. He pointed to a link between vitamin D levels and a destructive immune system overreaction called a “cytokine storm”.

Ali Daneshkhah, a postdoctoral research associate in Backman’s laboratory, and the paper’s first author, said: “These can severely damage lungs and lead to acute respiratory distress syndrome and death in patients.

“This is what seems to kill a majority of covid-19 patients, not the destruction of the lungs by the virus itself. It is the complications from the misdirected fire from the immune system.”

This is where the study’s findings come into play. Not only can vitamin D boost the immune system, it also plays a role in balancing its response to disease and inflammation. A healthy level of vitamin D in the body can help avoid a potentially fatal immune overreaction, such as the dreaded cytokine storm involved in many coronavirus deaths.

Backman and his research team insist their findings don’t imply vitamin D is a magic bullet for covid-19. Maintaining a healthy level of it may or may not prevent you from contracting the virus, but it could influence the severity of your case if you do.

The paper advises people not to supplement with too high a dose of vitamin D as this can have severe side effects. We don’t need to raid the supplement aisle at Boots. In fact, it’s best to steer clear of such crowded spaces.

How to get more vitamin D

It’s useful to know our body produces vitamin D when our skin is struck by sunlight. Ten to 15 minutes in the sun per day should be enough for your body to get most of its vitamin D.

A quick mid-morning run should do the trick. Just remember to keep a distance of two metres between yourself and others at all times.

If you can’t go outside, you can eat more vitamin D-rich foods and take a daily supplement. Here are some of the best dietary sources of vitamin D.


A 100g serving of Atlantic salmon contains 526 IU of vitamin D, or 66% of your recommended daily intake (RDI). If you can afford to, it’s worth splurging on wild-caught from time to time – the same size of serving contains 988 IU of vitamin D or 124% of your RDI.

Herring, sardines and tuna

These are quick and easy sources of vitamin D, especially tinned, which is ideal if you can’t go shopping as often as you’d like. These provide between 170 and 270 IU of vitamin D, or almost 28% of your RDI.

Cod liver oil

This is a more palatable option for those of us who don’t like eating fish. Clocking in at about 448 IU per teaspoon (or 56% of RDI), it’s also a great source of vitamin A and omega-3 fatty acids. These keep your hair, skin and nails healthy and shiny.

Egg yolks

They pack a hardy nutritional punch, with an average of 37 IU per serving. However, eggs from pasture-raised chickens who spend their lives running around in the sun have three to four times the amount of vitamin D.


Excluding fortified foods, mushrooms are the only reliable plant source of vitamin D. The best types are crimini, portobello and button mushrooms, which contain up to 450 IU per 100g serving.

Fortified food

Fortunately for those of us who are vegan, vegetarian or simply don’t like fish, many foods nowadays are fortified with vitamin D. Some of the best options include dairy and plant milk, yogurt, orange juice, breakfast cereal and oatmeal.


Healthy vitamin D levels can balance your immune response to covid-19, preventing it from going into overdrive and wreaking havoc on your body. That’s about the extent of the recent findings.

As always, other factors come into play such as age and a slew of health conditions. Think twice before raiding the supplements aisle and overdosing on vitamin D. From what I hear, the effects aren’t pretty.

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