In Ireland, researchers called for vitamin D supplementation to reduce severity of COVID-19 symptoms, In France, studies found that elderly patients who have previously taken vitamin D3 supplements were more likely to survive COVID-19. In an open letter to world governments, researchers from UK, US and Europe called for immediate increased vitamin D intake for healthy adults, in a bid to reduce COVID-19 infections, hospitalisations and deaths.
In Asia, individual countries such as China have reported association between vitamin D deficiency and COVID-19 infection and mortality, where serum vitamin D concentration was found to be significantly lower in COVID-19 patients than in controls.
Researchers from Sri Lanka, Australia, India believed that this is the first analysis of vitamin D prevalence with COVID-19 infections and mortalities across Asia, comprising 24 countries from Middle East to South East Asia.
This study also assessed the effect of confounding factors such as obesity and diabetes which are also known to be additional risk factors for COVID-19 infection and mortality.
The findings were published in the Diabetes & Metabolic Syndrome: Clinical Research & Reviews journal.
Researchers collected data on COVID-19 infections and mortalities among the 24 Asian countries from the Worldometer website as of December 31st, 2020. Data included records derived directly from official government reports of individual countries and/or indirectly through reliable local media resources.
Information on the prevalence of vitamin D deficiency in each Asian country was retrieved through literature searching on PubMed and Google scholar.
Vitamin D deficiency is defined as a serum concentration of less than 20 ng/ml (25(OH)D).
For the confounding factors, obesity and diabetes prevalence were extracted from the World Health Organization (WHO)’s non-communicable disease country profiles. Obesity was defined as BMI levels more than or equal to 30 kgm−2 and diabetes as fasting plasma glucose concentration more than or equal to 7.0 mmol/l.
Western Asia vs South East Asia
It was observed that all the Western Asian countries such as Qatar, Lebanon and Kuwait reported higher values for both COVID-19 infections and mortalities compared to South East Asian countries like Vietnam, Singapore and Brunei.
COVID-19 infections were lowest in Vietnam at 15 infections per one million people, while Bahrain had the highest (53,679/1 million).
For COVID-19 mortalities, similar Vietnam reported the lowest number at 0.4 deaths/1 million while the highest number occurred in Iran at 655 deaths/1 million.
In terms of deficiency, it was found that more than 50% of the adult population in some 18 countries were vitamin D deficient. The lowest vitamin D deficiency was reported in Vietnam with only 2.0% and the highest was reported in Oman at 87.5%.
Researchers said these findings were prominent considering the Gulf region receives endless supply of sunlight yet has a high prevalence of vitamin D deficiency, probably due to the cultural and social habits limiting exposure to sunlight.
The prevalence of diabetes across the 24 countries were around the same levels, at 10% of the population. Obesity prevalence was highest in Bahrain (35%) and lowest in Vietnam (2%).
COVID-19 and vitamin D deficiency
Across all 24 countries, the study reported that vitamin D deficiency was significantly associated with COVID-19 infections (p = 0.01) and mortalities (p = 0.01).
COVID-19 infection and mortality were also more significant in people with obesity and diabetes.
COVID-19 is caused by a dysregulation of the immune system, hence it was key to restore immune balance and prevent the hyper-inflammatory cytokine storm to combat the virus.
Researchers recommended vitamin D as a protective effect in reducing the infectivity and mortality of COVID-19.
“People who are deficient in vitamin D may receive daily or weekly supplementation as it is studied to protect against acute respiratory tract infections. The population at higher risk of vitamin D deficiency during this global pandemic should consider taking vitamin D supplements to maintain the circulating 25(OH)D in optimal levels (75–125 nmol/l),” they explained.
One limitation of this study was the obesity and diabetes prevalence date which were extracted from the WHO databases, while accurate, but may be out-dated.
Researchers said it would have been more precise to collect data for each country individually, as BMI values may differ by regions.
“Obesity cut off values may differ from this database (BMI<30 kgm2) when focused on Asia as the cut off value would be lower due to the different body composition.”
Source: Diabetes & Metabolic Syndrome: Clinical Research & Reviews
“Impact of the vitamin D deficiency on COVID-19 infection and morality in Asian countries”
Authors: Ranil Jayawardena, et al.