Vitamin D Supplements & Covid19

26th March 2020

Vitamin D levels tend to be low in people living in Northern Europe during winter months.

Vitamin D is synthesised in the skin by the action of ultraviolet in sunlight. Although it is also present in the diet – particularly oily fish – synthesis in the skin is the major natural source. As a consequence many people in Northern Europe tend to have low vitamin D levels in the winter.

Vitamin D levels also tend to be low in people with chronic disorders of the gut, liver and pancreas.

Vitamin D deficiency has been shown to be common and to correlate with poorer outcomes in patients with inflammatory bowel disease. It is common in patients with undiagnosed coeliac disease, although this usually corrects on a gluten-free diet, and is also common in patients with chronic pancreatitis, and in other conditions, including liver cirrhosis where fat malabsorption occurs (vitamin D is a fat soluble vitamin).

Vitamin D is important for the immune system, not just for bones.

Vitamin D is best known for its important effects on calcium metabolism and bone formation. However, it also has important effects on the immune system. It helps macrophages (a type of white blood cell that is important in defence against bacteria and viruses) kill pathogens they have engulfed. It also has anti-inflammatory effects and has been shown to suppress the cytokine (inflammatory) response to viruses. This might be beneficial in Covid-19 where severe lung damage can result from an inflammatory “cytokine storm” in response to the virus.

Vitamin D deficiency increases risk of infection by respiratory viruses.

It has been shown that people with low vitamin D levels are more susceptible to viral respiratory infections and that regular supplementation reduces the risk.

Vitamin D supplementation might help to reduce risk of severe Covid19 illness – although there is no direct evidence to support this.

No studies of vitamin D supplementation have yet been performed in relation to Covid-19 but its protective effect against respiratory viruses and its ability in the laboratory to reduce inflammatory cytokine responses to viruses suggests that regular vitamin D supplementation might help to reduce risk of severe Covid19 illness.

If you do take vitamin D supplementation the dose is very important.

Vitamin D overdosing is harmful – it can cause dangerous increases in blood calcium and can also potentially have unwanted impacts on the immune system – dose is therefore important. Current evidence suggests that for adults a regular daily dose of 25 micrograms (1000 units) is likely to be optimal. There is good evidence that this is safe (daily doses of up to 4000 units are regarded as safe in adults). In healthy adults there is some evidence that daily dosing of more than 1000 units actually has less beneficial effect although higher doses eg 2,000 units per day may sometimes be used in patients with proven vitamin D deficiency. The National Institute for Health and Care Excellence (NICE) already recommends that all UK adults should take 400 units daily – evidence in relation to respiratory infections currently suggests that a somewhat higher dose of 1000 units per day (for adults) may be optimal.

In summary:

  • most UK adults are vitamin D deficient in the winter months.
  • Vitamin D deficiency is particularly common in people with chronic disorders of the intestine, pancreas or liver.
  • Regular daily dosing of vitamin D3 1,000 units without calcium (typically one capsule or tablet) is safe and usually sufficient to correct this
  • Low levels of vitamin D are associated with increased risk of respiratory viral infection
  • Vitamin D supplementation has been shown to reduce risk of respiratory viral infection
  • Laboratory studies show that vitamin D reduces the cytokine response to respiratory viruses – this might be helpful in reducing the risk of serious lung damage in Covid19 infection, although this is unproven.

Note – Guts UK is a UK Charity and has no commercial links with suppliers of vitamin D.

Click here for references


  1. Gubatan J, Chou ND, Nielsen OH, Moss AC. Systematic review with meta-analysis: association of vitamin D status with clinical outcomes in adult patients withinflammatory bowel disease. Aliment Pharmacol Ther. 2019;50:1146-1158. doi: 10.1111/apt.15506. Open access.
  2. Zingone F, Ciacci C. The value and significance of 25(OH) and 1,25(OH)vitamin D serum levels in adult coeliac patients: A review of the literature. Dig Liver Dis. 2018;50:757-760. doi: 10.1016/j.dld.2018.04.005. Not open access.
  3. Martínez-Moneo E, Stigliano S, Hedström A, Kaczka A, Malvik M, Waldthaler A, Maisonneuve P, Simon P, Capurso G. Deficiency of fat-soluble vitamins inchronic pancreatitis: A systematic review and meta-analysis. Pancreatology. 2016;16:988-994. doi: 10.1016/j.pan.2016.09.008. Not open access.
  4. Konstantakis C, Tselekouni P, Kalafateli M, Triantos C. Vitamin Ddeficiency in patients with liver cirrhosis. Ann Gastroenterol. 2016;29:297-306. doi: 10.20524/aog.2016.0037. Open access.
  6. Zittermann A, Pilz S, Hoffmann H, März W. Vitamin D and airway infections: a European perspective.Eur J Med Res. 2016;21:14. doi: 10.1186/s40001-016-0208-y. Review. Open access.
  7. ZdrengheaMT, Makrinioti H, Bagacean C, Bush A, Johnston SL, Stanciu LA. Vitamin D modulation of innate immune responses to respiratory viral infections. Rev Med Virol. 2017;27. doi: 10.1002/rmv.1909. Open access.
  8. Martineau AR, Jolliffe DA, Hooper RL, Greenberg L, Aloia JF, Bergman P, Dubnov-Raz G, Esposito S, Ganmaa D, Ginde AA, Goodall EC, Grant CC, Griffiths CJ, Janssens W, Laaksi I, Manaseki-Holland S, Mauger D, Murdoch DR, Neale R, Rees JR, Simpson S Jr, Stelmach I, Kumar GT, Urashima M, Camargo CA Jr. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583. doi: 10.1136/bmj.i6583. Open access.


Read more posts...

Your Comments: Mental Health Awareness Week

Digestive symptoms and conditions can have a real impact upon every-day life, that our community sometimes find others can underestimate. Managing pain, being unable to predict symptoms from day-to-day and anxiety surrounding accessing near-by toilet...

22nd May 2020

Mental Health Awareness & Digestive Diseases

Mental Health Awareness Week 2020 falls at a challenging time for many across the globe. The team at Guts UK recognise the impact that digestive diseases can have on your mental health, and this week...

20th May 2020

World IBD Day

On World IBD Day every year, patient organisations come together from all over the globe to raise awareness of Crohn’s disease & Colitis. Guts UK is proud to fund over 10 current active research projects into...

19th May 2020

Eosinophilic Awareness Week 2020

This week, Guts UK wants to raise awareness, encourage collaboration and research into eosinophilic diseases. What are Eosinophilic Diseases? Eosinophilic Diseases (pronounced ee-oh-sin-oh-fil-ik) that affect the gut are identified by the presence of a type...

18th May 2020

World Barrett’s Day

Guts UK is one of the many worldwide charities collaborating to raise awareness of Barrett’s oesophagus for the first ever World Barrett’s Day – 16th May 2020. What is Barrett’s oesophagus? Around 10% of persistent...

16th May 2020

Coeliac Awareness Week – Lockdown as a Coeliac Dietitian

Cristian Costas, coeliac dietitian shares his experience supporting patients with coeliac disease during these challenging times. What was your role before lockdown and COVID-19? I was running the dietetic-led coeliac service at Bradford Teaching Hospitals...

12th May 2020

Cancer Treatment & Covid-19

On Monday, the Health Secretary announced that hospitals are now restarting vital services including cancer care. An important part of our work at Guts UK is campaigning, raising awareness and calling for more research into...

29th April 2020

Creon 25k – Potential Short Term Stock Issues

Guts UK is the only UK charity funding a research fellowship into pancreatitis. Pancreatitis is a priority for our charity, so each November we’re proud to run a month-long Kranky Panky Pancreatitis Awareness Campaign. We...

22nd April 2020

World Digestive Health Day 2020

Happy World Digestive Health Day! Today is a much awaited day on the Guts UK calendar. Guts UK is the only UK charity funding research into the digestive system from top to tail; the gut,...

29th May 2020