COVID-19 is an infectious disease caused by the recently discovered e novel coronavirus (or SARS-CoV-2). And within a few months, the disease has spread globally at the speed of light, while transforming our societies and affecting our day-to-day lives.
At present, there exist several theories and hypotheses about ways in which this fast-spreading virus could be controlled. One of the ways put forward to combat the disease is higher consumption of vitamin D other than having cruciferous vegetables in your diet. Various groups of doctors and researchers have nudged at the possibility that higher doses of vitamin D could reduce COVID 19 hospitalisations. In this blog, we try to examine whether the claim that vitamin D can reduce the severity in COVID patients is a myth or fact.
Many researchers and doctors state that not only does vitamin D help against rickets, but it also is a key component required for the effective functioning of our immune system. A doctor also stated that “the innate immunity, the first line of defense when the pathogen invades our body, strengthens if we have high levels of vitamin D in our body”.
A study conducted in elderly African American, patients having diabetes mellitus, and chronic lung and cardiovascular diseases shows that the disease is severe and the mortality rates are higher in the patients having low vitamin D levels. Another ecological study also suggests that in high altitude places and geographies that see winter season a major part of the year, inhabitants have a risk of having low levels of vitamin D and this may also be associated with high mortality rates in COVID patients.
Lower than normal levels of vitamin-D can lead to a condition called hypovitaminosis D and an increased risk for viral respiratory infections. Calcifediol, also called 25-hydroxyvitamin D3, is the main metabolite of vitamin D.
How the virus enters and affects the human body
When the coronavirus enters the body, it activates the immune and inflammatory response, which involves both T cells and B cells. The SARS-CoV-2 virus infects respiratory epithelial cells through a receptor called ACE2, which is a protein called the angiotensin-converting enzyme 2. The ACE2 receptor provides an entry point for the coronavirus to attach to and infect human cells. The spike-like proteins on the surface of the virus bind to ACE2, just as a key fits perfectly into a lock.
The ACE2 receptor protein is present in epithelial cell lining in various cell types and tissues in our body, including our lungs, heart, kidneys, blood vessels, and liver. The ACE2 receptors are present at the site of oxygen and carbon dioxide exchange (between the lungs and blood vessels) in the epithelium of the lungs.
And the binding of SARS-CoV-2 to ACE2 receptors triggers the release of several proinflammatory cytokines such as IL-6 and chemokines. The release of these cytokines and chemokines attract macrophages, monocytes and T-cells, which, in turn, releases IFN gamma, further contributing to inflammation. In the affected host, this phenomenon causes a “cytokine storm”, which leads to the activation of auto-amplifying production of cytokines, excessive activation of immune cells, and leads to further organ damage.
The role of Vitamin D
Vitamin D is converted into calcitriol by enzyme and it regulates both innate and adaptive immunity, through the vitamin D receptor (VDR) and CYP27B1, both of which are expressed in immune cells. The vitamin D metabolites decrease the expression of cytokines, including IL-6, TNF alpha and IFN beta, which occurs due to viral infection.
The Vitamin D metabolites, however, do not affect the replication of respiratory viruses. Vitamin D also has other anti-inflammatory activities such as the regulation of macrophage chemotactic protein 1, interleukin 8, type 1 interferon, TNF alpha and lowering of reactive oxygen species.
In the last few months, researchers and doctors around the globe have conducted several clinical trials in COVID 19 patients to understand the effect of vitamin D supplementation.
An investigation of almost 11,000 patients shows that vitamin D is effective in reducing the risk of acute respiratory illness and influenza. Three controlled trials were conducted which explored the effect of vitamin-D in COVID 19 patients on mortality, as a primary outcome and hospital complications and time to recovery in patients as a secondary outcome.
The results of another clinical trial conducted in Spain, which was the first clinical evidence addressing the efficacy of Vitamin-D in combating COVID-19, were published in the Journal Of Steroid Biochemistry And Molecular Biology.
In this trial, 76 COVID-19 patients were randomly chosen, out of which 56 patients were given oral calcifediol (vitamin D3 in the liver is converted to calcifediol), and 26 patients (comprising the control group) were not given any calcifediol.
Out of the 26 patients in the control group, 13 (50 %) were admitted to ICU and two of them subsequently died. In the calcifediol group, on the other hand, only one out of 76 patients, that is 2%, was admitted to ICU and none of them died.
Dr Gareth Davies, a PhD in Medical Physics from Imperial College London, believes that the recommended daily intake of Vitamin-D in the UK should be increased to 4000 IUs during this pandemic from the earlier recommended daily intake figure of 400 IUs.
Another study of COVID-19 patients in Spain has found that almost 80 percent of patients infected with COVID 19 had a Vitamin-D deficiency. This study took into account a total of 216 patients who were admitted in Hospital Universitario Marques de Valdecilla. The study was published in the Journal of Clinical Endocrinology and Metabolism in October and also discovered that men had lower vitamin D levels in their than women.
Researchers at the Queen Mary University of London are also conducting trials to test whether daily intake of vitamin D can help fight against the disease. Through the study, they aim to assess the effects of higher than regular doses of vitamin D and the investigators have also stated that the participants will be asked to take vitamin D pills daily for 6 months if found deficient in vitamin D.
Vitamin D has always remained an important dietary supplement due to its role in our body, especially in the immune system. Vitamin D also has the potential to be a breakthrough in the treatment of the coronavirus as it is a low-cost supplement, easily available, and poses the lowest risk to our body.
Although the above-mentioned studies have shown significant results, most of these studies had very small population sizes and the severity of the disease in patients is not known. Vitamin D does not cure COVID-19 but it does boost our immune system to fight against the virus.
The question of whether vitamin D plays a major role in fighting this highly infectious disease, and can it reduce the mortality rates, cannot be answered just yet.