Who is most at risk from COVID-19?

We know at least three groups of people are at particular risk of dying from COVID -19:

  • People in care homes and the housebound elderly
  • People from a BAME (Black and Minority Ethnic) background
  • People who are obese, especially if they have associated underlying health conditions like Type 2 Diabetes 

Who is most at risk of Vitamin D Deficiency?

The same three groups are at particular risk of Vitamin D deficiency.

For people in care homes and the housebound elderly this is because they don’t have enough access to sunshine, the main natural source of Vitamin D. For people from a BAME background their dark skin (which helps protect them in countries with year round sunshine) means it is more difficult for them to make Vitamin D from the lower levels of sunshine in the UK. For people who are obese, one of the things fat cells do is to reduce Vitamin D.

This is confirmed by a recent study by Surrey and Southampton universities which compared the blood samples of 1,300 adults on the UK Biobank health-monitoring programme, of whom 580 had tested positive for the coronavirus. Vitamin D levels among white people were typically 53 per cent higher than among people of black and ethnic minority backgrounds, while people of healthy weight had 25 per cent more than the obese. 

Is there a connection?

COVID-19 is too recent for there to be any peer reviewed evidence available yet. But what we do know is:

  1. COVID-19 is an acute respiratory disease
  2. Vitamin D protects against acute respiratory tract infection (according to a systematic review of the evidence published in the BMJ in 2017)
  3. Vitamin D deficiency is common in people who develop acute respiratory distress syndrome and appears to contribute to its development (according to a 2014 study)
  4. Medically prescribed Vitamin D supplementation is safe (according to the systematic review mentioned above) although you should check with your doctor before taking more than 10 mcg per day. 

Access to sunshine, as the main natural source of Vitamin D?

Researchers from the University of Liverpool and Trinity College Dublin compared COVID-19 mortality per million around the world in relation to latitude. They found that countries below 35 degrees North have relatively low mortality (although this may change given rising levels of COVID-19 in Latin America). Conversely most countries above 35 degrees North (the latitude above which people don’t receive sufficient sunlight to retain adequate vitamin D levels during winter) had relatively high mortality. They concluded this suggests a possible role for vitamin D in determining outcomes from COVID-19.

Reduces the risk of a cytokine storm?

Research by NorthWest University in the USA, based on data from 10 different countries, concluded, ‘Our finding suggests that Vitamin D may reduce COVID-19 severity by suppressing cytokine storm in COVID-19 patients’. A cytokine storm is when our immune system over reacts, potentially causing damage to vital organs in the body.

The researchers noted that patients from countries with high COVID-19 mortality rates, such as Italy, Spain and the UK, had lower levels of vitamin D compared to patients in countries that were not as severely affected.

They estimated that patients with normal Vitamin D had a 15.6% lower risk of severe COVID-19 than patients with severe Vitamin D deficiency – not a huge difference but helpful, if true.

Vitamin D deficiency – not always in the obvious countries?

Researchers at Queen Elizabeth Hospital Foundation Trust, the University of East Anglia and Anglia Ruskin University recently compared the average vitamin D levels of 20 European countries with COVID-19 mortality rates — and found “significant relationships” between vitamin D levels and the number of deaths caused by this infection.

Italy and Spain have both experienced high COVID-19 mortality rates. The new study found that, surprisingly, both countries had lower average vitamin D levels than most northern European countries.  They observed that this is partly because people in southern Europe, particularly the elderly, avoid strong sun, while skin pigmentation also reduces natural vitamin D synthesis.

Conversely, the highest average levels of vitamin D were found in northern Europe, due to the consumption of cod liver oil and vitamin D supplements, and possibly less sun avoidance.  Scandinavian nations are among the countries with the lowest number of COVID-19 cases and mortality rates per head of population in Europe.

Reader Beware 

It is important to note that: 

- The findings referred to have just been published and haven’t had time to be peer reviewed (i.e. reviewed by a couple of experts in the field) to check how robust they are. 

- Because there’s a correlation between two factors (like Vitamin D deficiency and deaths from COVID-19) this doesn’t necessarily mean one is causing the other. It could just be a coincidence, for instance. 

- Other factors may be at work. For example, elderly people in care homes and obese people are more likely to have underlying health conditions that increase the risk of complications in the event of COVID-19. We also know that, in people who are obese, it isn’t just that fat cells reduce Vitamin D. Fat cells also release cytokines, which are inflammatory and fat tissue is also a potential target for the virus (as it upregulates an enzyme the COVID virus can bind to)  

So what should we conclude?

  • The research doesn’t suggest that Vitamin D is a magic bullet which will prevent us from getting COVID-19.
  • However, there seems to be a correlation between Vitamin D deficiency and increased risk of serious complications and death for patients who have COVID-19.
  • So, while we’re waiting for the results of current research to be peer reviewed, it would seem sensible to consider prescribing Vitamin D, at least for those for whom the usual main natural source (i.e. daily sunlight) isn’t available or effective - alongside other reasonable precautions.
  • That would include elderly people in care homes, frontline health and care workers from BAME backgrounds, and obese hospital patients.
  • It may not stop us getting COVID-19 but at 10 – 25 mcg a day it shouldn’t harm and it may help reduce the risk of serious complications and death.

 Michael Baber  May 2020