Gastrointestinal microbiota: A predictor of COVID-19 severity?

Table 4 Nutraceuticals used to improve disease severity and outcomes of coronavirus disease 2019 patients

Nutraceuticals	Number of patients with vs without nutraceutical agent	Results	Ref.
Probiotic combined Bifidobacterium, Lactobacillus and Enterococcus	179 vs 196	Shorter time to clinical improvement (fever, hospital stay, viral shedding) in hospitalized COVID-19 subjects	[153]
Probiotic Lactobacillus hamnosus GG	566 vs 566	Extended time until the development of infection with COVID-19, reduced the severity of the disease, changed the composition of the intestinal microbiota in the household contact infected with COVID-19 (after 28 d)	[154]
Probiotic Lacticaseibacillus rhamnosus, Bifidobacterium bifidum, Bifidobacterium longum subsp. infantis, Bifidobacterium longum subsp. longum	99 vs 101	The duration of diarrhea was shorter in patients who received the probiotic than in those who did not. No significant effect on mortality, no change in most biomarkers in patients with COVID-19 in hospitalized patients (at 14 d)	[155]
Vitamin D3 (single oral bolus of 80000 IU)	57 vs 9	The severity of COVID-19 decreased. Improved survival rate	[156]
25-hydroxyvitamin D3	50 vs 26	Reduced the need for treatment in the ICU in patients hospitalized due to proven COVID-19	[157]
Quercetin	21 vs 21	Decreased virus clearance, frequency of symptoms and level of LDH and ferritin parameters	[158]

ICU: Intensive care unit; LDH: Lactate dehydrogenase; COVID-19: Coronavirus disease 2019.