Can Vitamin D protect against COVID-19?

The emergence of COVID-19, the newest coronavirus, has raised some important questions for doctors and scientists about who is at risk. For example, men appear to more vulnerable than women. But that isn't the only puzzle for the medical profession. Virologists and epidemiologists experts are asking:

• Why do some countries have a higher death rate from COVID-19 than others?

• Why in the UK and the US are black, Asian and other minority groups (BAME) so vulnerable to coronavirus?

• How do some people shrug off COVID-19 with relatively few ill-effects, while others are seriously, sometimes fatally affected?

The answer to these questions could be related to Vitamin D – or rather, a deficiency of the sunshine vitamin. 

The centre for evidence-based medicine (CEBM) in Oxford say that for most of us with normal levels there is little to no evidence that additional supplements of vitamin D work for COVID-19, but state; "There is some evidence that daily vitamin D3 supplementation over weeks to months may prevent other acute respiratory infections, particularly in people with low or very low vitamin D status"

What is the hormone vitamin D?

Vitamin D is a hormone mostly produced in the skin in response to sunlight, and is also absorbed from food eaten. Around 10% of vitamin D is absorbed from food as part of a healthy balanced diet. It is not a single compound, but a name actually given to a group of vitamins, including the following:

• Vitamin D2 (ergocalciferol, found in plants) and
• Vitamin D3 (cholecalciferol, found in animal tissues)

These molecules are not active until we convert them in the liver and then kidneys. The liver converts vitamin D3 to 25-hydroxycholecalciferol, which is weakly active. The kidneys then convert this to either 24,25-dihydroxycholecalciferol, which is also weakly active, or to 1α,25-dihydroxycholecalciferol, the most active form of vitamin D.

Vitamin D is important for bone metabolism, and regulates calcium concentrations in the blood. Vitamin D increases absorption of calcium from the gut and reduces the amount lost by the kidneys. Many tissues have vitamin D receptors, and vitamin D may have other roles.

We already know how useful Vitamin D is for the menopause and in preventing osteoporosis, but now it appears that ensuring adequate amounts of the vitamin may even be potentially lifesaving.

The connection between Vitamin D deficiency and COVID-19

A study by the Vrije Universiteit Amsterdam has discovered that countries with low vitamin D levels were also the countries with the highest mortality and COVID-19 infection rates.

Perhaps we shouldn’t be surprised. After all, we have known for some time that Vitamin D reduces acute respiratory infections and more evidence that it is helpful in fighting off illness  is mounting.

A ten-week trial from the University of Granada is also underway after a recent study from The Irish Longitudinal Study on Ageing (TILDA) at Trinity College, Dublin found that adults taking vitamin D supplements slashed the risk of having at least one acute respiratory infection from 60 per cent to 32 per cent.
Preliminary research from the Queen Elizabeth Hospital Foundation Trust and the University of East Anglia has compared average vitamin D levels in 20 European countries with COVID-19 infection rate and mortality. The countries with low vitamin D levels were also the countries with the highest rates of mortality and COVID-19 infection.

Natural immunity requires vitamin D

Our natural immunity to coronaviruses primarily requires the presence of activated T-cells to fight the infection. T-cells are only effective if they can bind to vitamin D.

Boosting chances of survival from Covid-19

Many doctors are becoming quite excited by vitamin D’s potential to make a difference to COVID-19 patients. Dr JoAnn Manson, professor of medicine at Harvard Medical School and Brigham and Women's Hospital believes Vitamin D can potentially make a difference to survival rates from COVID-19.

‘We've known for a long time that it's important to avoid vitamin D deficiency for bone health, cardiometabolic health, and other purposes,’ she says. ‘There's emerging and growing evidence that vitamin D status may be relevant to the risk of developing COVID-19 infection and to the severity of the disease.’

Dr Manson adds: ‘Vitamin D is important to innate immunity and boosts immune function against viral diseases. We also know that vitamin D has an immune-modulating effect and can lower inflammation, and this may be relevant to the respiratory response during COVID-19 and the cytokine storm that's been demonstrated.’

What’s the evidence vitamin D can help patients suffering from COVID-19?

• Lab studies of respiratory cells have shown vitamin D improves immune function
• Research shows that patients with respiratory infections tend to have lower blood levels of 25-hydroxy-vitamin D.
• Observational studies from South Asian hospitals have shown that in COVID-19 patients vitamin D deficiency was much higher among those with severe cases, compared with those mildly affected – there is an eightfold higher risk of having severe illness among those who entered with vitamin D deficiency compared with those who had sufficient vitamin D levels.

These findings would partly explain why BAME British people – who usually have darker skin which does not produce Vitamin D as easily as paler skin – seem to be so adversely affected.

How much Vitamin D should I take to protect against the coronavirus?

According to the NHS, supplementing with 10 micrograms (400 IU) a day will be enough for most people. The problems is, many health experts believe many people are deficient without realising. Ideally you should check your levels with a blood test. 

For adults with vitamin D levels below 30 ng/mL, the Endocrine Society guidelines recommend a daily intake of 1,500–2,000 IU to restore healthy levels of vitamin D. There are also treatment options where people with vitamin D deficiency receive 50,000 IU weekly or monthly instead of taking a daily dose.