Impacts of vitamin C and D supplement on COVID-19 treatment: possible patho-mechanisms and evidence from different countries

The Egyptian Journal of Bronchology

Table 2 Effectiveness of vitamin D supplement in COVID-19 treatment in different populations

Treatment	Key findings	References
Vitamin D deficiency	Increased mortality	[36, 38]
	Increased COVID-19 susceptibility	[39]
	Intensified acute respiratory distress syndrome (ARDS)	[39]
	Increased rate of infection	[40]
Vitamin D supplement	Lower rate of ICU need	[41]
	Lower level of fibrinogen	[42]
	Lower level of ARDS	[39]
	Lower severity	[43]
	Increased level of anti-inflammatory cytokines and decreases levels of pro-inflammatory cytokines, boosts the production of natural antimicrobial peptides, and activates cells like macrophages that can kill SARS-CoV-2	[39]
	Increased human cationic antimicrobial protein (hCAP18) in pregnant women, play role in the post-SARS-CoV-2 infection treatment	[17]
	Positively impacts on the innate and adaptive immune system. Significantly reduce pro-inflammation by selectively inhibiting inflammatory cytokines, decreasing leukocyte infiltration, increasing memory and regulatory T cells, and lowering the lymphocyte ratio	[44]
	Lower viral multiplication	[45]