Vitamin D deficiency has been linked to more severe illness and an increased fatality rate due to COVID-19, the disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Observational studies at the AZ Delta General Hospital in Roeselare, Belgium, at the Hospital Universitario Marquis de Valdecilla in Spain, as well as at the M L B Medical College in India, have found that a significant number of COVID-19 patients presented with vitamin D deficiency at admission.
In Spain over 80% of 216 COVID-19 patients, in Belgium 59% of 186 patients, and in India 58% of 154 patients included in the observational studies were vitamin D deficient. In Belgium, the admission of COVID-19 patients with vitamin D deficiency (below 20 ng/ml) was associated with an almost fourfold increase in the odds of dying from the disease. In India, the fatality rate in vitamin D deficient patients was 21% vs 3.1% for patients with sufficient levels. Doctors also observed a higher inflammatory response in vitamin D deficient patients, and a clear correlation between vitamin D deficiency and advanced stages of the disease.
These observations suggests that deficiency in vitamin D may indicate the loss of the protective action of vitamin D on the immune system and against the excessive inflammation caused by COVID-19.
Vitamin D’s most well-known function is to maintain normal blood levels of calcium. It acts as facilitator for the absorption of calcium from the gut, which is essential to form and maintain strong bones. However, vitamin D also has other functions in the body, such as playing an essential role in the optimal functioning of the immune/inflammation system. Sufficient levels of vitamin D are required to trigger T-cells (the protective “killer” cells of the immune system) into action, otherwise these cells remain dormant and inactive.
Vitamin D also plays a role in reducing the cytokine storm, an overreaction of the immune system in the production of inflammatory cytokines. In fighting infections, the immune system secretes proteins called cytokines as a defense mechanism to help the body fight off the intruder. In a phenomenon called a “cytokine storm”, the immune system goes into extreme overdrive, in which a massive influx of cytokines leads to the dysregulation of the immune system and can also attack the body’s own tissues, not only the virus. Severe COVID-19 is characterised by a “cytokine storm”.
These observational clinical studies suggests that adequate levels of vitamin D can play a protective role in the severity and mortality of COVID-19. Conclusive evidence may soon be found in a phase 3 clinical trial, called the CORONAVIT trial, that is currently being conducted by Professor Adrian Martineau and team at the Queen Mary University of London. The aim of the study is to determine whether identifying and correcting vitamin D deficiency can reduce the risk of developing COVID-19 and other respiratory infections.
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