Abstract:
Thousands of people across many nations lost their lives due to COVID-19. This disease is caused by a novel coronavirus named SARS-CoV-2. Besides, we always have another massive threat. It is obesity, which causes about 2.8 million deaths each year across the globe. This pandemic has just highlighted obesity and its related complications. Evidence shows that obesity is likely to cause the development of vitamin D deficiency. Moreover, inadequate Vitamin D level is independently associated with the aged and other diseases. To date, there is still no specific treatment or prevention for the SARS-CoV-2. Emerging evidence indicates that vitamin D has potential roles in the immune response against enveloped viruses including SAR-CoV-2. Optimal dosage is probably determined by the vitamin D receptor gene polymorphism. The likelihood that vitamin D may offer a more personalized and accessible strategy against COVID-19 should be taken into account.
Keywords: COVID-19, Vitamin D, Obesity and VDR gene polymorphism
COVID-19 caused thousands of deaths in the world. This global pandemic has significantly interrupted trade, business, and education. COVID-19 disease is caused by a novel coronavirus named SARS-CoV-2. The pandemic is caused by coronaviruses is not new during the last 20 years. Between 2002 and 2003, its sister, SARS-CoV-1, killed hundreds of people. An important lesson from these outbreaks is that different human populations showed disparities in susceptibility to these viruses. There is also a different death rate between women and men.  Moreover, young, healthy people also died of COVID-19 although this disease was previously thought for the elderly or those with pre-existing medical conditions such as obesity or diabetes. A question as to whether or not there is a common feature among different human populations.
Epidemiological studies currently estimate that at least one billion people with vitamin D deficiency (1), which is common with the elderly, but it is also associated with those, regardless of ageing, underlying medical conditions including obesity. To date, evidence confirmed that people with obesity may lead to the development of vitamin D deficiency (2).  An early report of the Intensive Care National Audit and Research Centre revealed 75% of patients with severe COVID-19 symptoms were overweight or obese (3). “It seems likely that the increased prevalence of obesity in Italy older adults compared to China may account for the differences in mortality between the two countries”, William Dietz and his colleague said (4). According to the Worth Health Organisation’ s classification, you are overweight if your body mass index (BMI) is equal to or more than 25. BMI is “a person’s weight in kilograms divided by the square of the person’s height in meters (kg/m2)”. Based on WHO-BMI classification, above 60% of people in the United States, the United Kingdom and other developed European countries are overweight (5). People with higher BMI also are at increased risk of various other diseases such as diabetes and heart diseases. Notably, studies demonstrated that obesity is strongly associated with an impaired immune system and severe risk of infections, but the mechanisms involved remain unknown(6). It is hypothesised that Vitamin D receptor gene polymorphism is responsible for the susceptibility to infections including COVID-19 among overweight or obese people.