Vitamin D: Role in Defence Against Respiratory Infections


Basis for role in COVID 19: Vitamin D: Role in defence against respiratory infections

  • COVID 19 is a disease caused by SARS-COV-2 virus which triggers a respiratory tract infection. While most people suffer from mild to moderate illness and recover without any special treatment. Others, with underlying diseases, elderly are more likely to develop severe diseases. The severity of COVID-19 is determined by the presence of pneumonia, severe acute respiratory distress syndrome (SARS-CoV-2), myocarditis, microvascular thrombosis and/or cytokine storms, all of which involve underlying inflammation.
  • Our body’s defence mechanism against such respiratory viral infections is mediated by vitamin D in many aspects. A lower vitamin D level has been found to be associated with decreased immune response to fight these viral infections. For instance, low vitamin D levels have been found to be associated with lower rise in cells which fight such infections like T regulatory cells and increase in cells which increase inflammation like IL-6 and TNF-alpha. (Fisher SA, 2019) (E Kenneth Weir, 2020)
  • Another complication that frequently occurs in COVID 19 patients are thrombotic complications, which occur due to abnormal blood clotting pathways in the body. Vitamin D is a mediator in such pathways and previous studies have demonstrated how vitamin D deficient patients were associated with an increased risk of thrombotic episodes. (Mohammad S, 2019)
  • Now given the scientific evidence we have; association of Vitamin D deficiency and increased morbidity and mortality is clearly established. Recent reports hypothesize that Vitamin D can reduce severity of COVID 19 with regards to pneumonia, acute respiratory distress syndrome and thrombotic complications. But said that it is necessary to understand the potential toxicity of vitamin D supplementation. The efficacy of vitamin D supplements in the prevention of acute respiratory tract infections has best been demonstrated with the chronic intake of low doses. (Martineau AR, 2017) Consequently, more than the usual daily supplement should only be taken under medical supervision.

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  1. E Kenneth Weir, A. T. (2020). Does vitamin D deficiency increase the severity of COVID-19? Clinical Medicine , Vol 20, No 4: e107–8.

  2. Fisher SA, R. M. (2019). The role of vitamin D in increasing circulating T regulatory cell numbers and modulating T regulatory cell phenotypes in patients with inflammatory disease or in healthy volunteers: A systematic review. PloS One, 14:e0222313.

  3. Martineau AR, J. D. (2017). Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. British Medical Journal , 356:i6583.

  4. Mohammad S, M. A. (2019). Emerging role of vitamin D and its associated molecules in pathways related to pathogenesis of thrombosis. Biomolecules, 9:649.

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