Vitamin D is a fat-soluble vitamin, which can be produced by exposure to sunlight. Ultraviolet B rays of the sun activate a protein in the skin called 7-dehydrocholesterol (7-DHC), which then is metabolized to the active form of vitamin D, which is vitamin D3. Dietary sources of vitamin D include egg yolk, milk, cheese, beef or calf liver and certain fish, certain cereals, soy milk, etc.
Vitamin D has a number of critical roles in your body. Among these, key functions include absorption of calcium that helps strengthen bones, efficient muscle movement, aids in nerve conduction to and from the brain. Besides, vitamin D is important for immunity as it helps regulate immune system to fight off invading pathogens like bacteria and viruses.
Vitamin D and viral infection
Various studies have shown that Vitamin D supplementation helps in reducing the susceptibility of developing a flu by acting as a physical barrier against the infection, or through modulation of natural and/or adaptive immunity mechanisms to reduce the risk of infection.2 Research also supports the finding that low levels of vitamin D increases the risk of community acquired-pneumonia.
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Association of vitamin D and COVID-19
The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), responsible for the COVID-19 disease, has been implicated in the deaths of over 3.5 million people globally.
Currently, there is no definite treatment available for this infection, hence, measures are being taken to discover aids that can help in reducing the risk of COVID-19. Moreover, owing to its high infectivity rate, the population also requires strategies that can limit progression and severity of COVID-19 infection.
A study published in the Endocrine Society’s Journal of Clinical Endocrinology & Metabolism, revealed that over 80% of COVID-19 patients in a hospital exhibited vitamin D deficiency. Therefore, the appropriate approach includes identification and treatment of vitamin D deficiency, particularly in high-risk individuals such as the elderly, patients with comorbidities, who are the main target population for the COVID-19.
Moreover, low levels of vitamin D are associated with 3.7-fold increase in the odds of dying from COVID-19 infection. Similar findings were seen in a Asian study that showed vitamin D insufficiency might compromise respiratory immune function, increasing the risk of severity and death rate in patients with COVID-19.
The most commonly encountered symptom in patients with COVID-19 is fever and dry cough, whereas severe forms of the disease can lead to the development of acute respiratory disease syndrome (ARDS). Researchers have found out that vast majority of COVID-19 ARDS patients had vitamin D deficiency, and these patients required longer mechanical ventilation and were associated with a higher death rate.
In addition to ARDS, heart failure is one of the fatal adverse outcomes of COVID-19. Studies have shown that Vitamin D supplementation, because of its protective effect on cardiac muscle cells, can be beneficial by reducing the risk of heart disease in these patients. Besides, comorbidities like high blood pressure, diabetes, obesity are considered as risk factors in increasing complications in people with COVID-19. Various studies have found strong correlation between deficiency of Vitamin D and increased risk of high blood pressure, diabetes and obesity. Hence, the hypothesis suggests that its supplementation can decrease the likelihood of complications in patients infected with COVID-19.
Furthermore, vitamin D deficiency has been related to reduced immune function and may enhance the cytokine storm and its supplementation may reduce complications related to cytokine storm and uncontrolled inflammation in people with COVID-19.
Hence as per some experts, one of the management strategies for reducing severity and death rate in patients with COVID-19 should include normalization of vitamin D levels.
Beneficial effects of vitamin D supplementation in COVID-19 patients
Numerous research have shown that having healthy levels of vitamin D can help keep your immune system healthy and may protect against respiratory illnesses.
Although there is currently no cure for COVID-19, studies have highlighted the importance of vitamin D supplements in the prevention and treatment of COVID-19 complications.
Some of the evidence suggesting benefits of vitamin D supplementation in COVID-19 are as follows:
- It has been reported that a high dose of vitamin D could reduce the need for intensive care stays in patients infected with COVID-19.
- Vitamin D supplementation was considered as a safe therapy, and it protected against acute respiratory tract infection.
- An Indian study suggested that high dose of Vitamin D3 (60000 IU) supplementation for seven days helps in coronavirus clearance.
- Although most older individuals, often have lower vitamin D levels and are most susceptible to COVID-19, a study showed that supplementation of vitamin D could decrease death rate in this group.
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The general recommendation is to supplement people who do not belong to a risk group, are healthy with a recommended daily dose (800 IU).
In view of the positive effects of vitamin D supplementation on vitamin D-deficient patients with COVID-19, few practical recommendations are as follows:
- Current public health guidelines for normalizing vitamin D status should always be followed
- Vitamin D levels should be measured in patients hospitalised with COVID-19 and should be supplemented to a level >30ng/mL (optimal 40–60ng/mL), specifically when the baseline level is <10ng/mL
- In Covid-19 patients with vitamin D levels under 20ng/mL, the recommended dose for correction of deficiency is 6000–7000 oral IU/ day for 6–8 weeks. For maintenance, the dose varies from 2000 to 3000 oral IU/day according to the age and clinical condition of the individual.
Although India is a subtropical country with sufficient sunlight, vitamin D deficiency is extremely common. It is crucial for people to understand the importance of Vitamin D so that they can take relevant supplements to fill the gaps. Vitamin D will not prevent a patient from contracting the COVID-19 infection; however, it may reduce complications and prevent death in those who are infected.
It is hard to ascertain the most appropriate beneficial dose for COVID-19, it is evident that vitamin D deficiency is harmful, and can be easily addressed with implementation of low-cost and low-risk vitamin D supplementation. It is unclear how soon the majority of the population will receive vaccines, routine vitamin D supplementation to high-risk people such as the elderly, children, those who are malnourished, and those living in overcrowded environments can be a worthwhile exercise.