Nigella Sativa in the Prevention and Treatment of COVID-19 and Respiratory System Diseases: A Systematic Review and Meta-analysis

Abs tractThis systematic review and meta-analysis aimed to determine the effects of Nigella sativa (NS) on respiratory diseases and COVID-19.The identified search terms were used to search PubMed, Scopus, and Web of Science, the Cochrane Library, Ovid, Google Scholar, and EBSCO CINAHL databases through 18 June 2022.The risk of bias was assessed using Cochrane's ROB2 and ROBINS scales.The metaanalysis and systematic review included 16 studies with a total of 1991 participants.Among the publications included in the study, 11 were randomized controlled trials, 2 were non-randomized clinical trials, 1 was a single-group clinical trial, 1 was a case/placebo study, and 1 was a non-randomized survey study.Nigella sativa was found to have a positive effect on COVID-19 [odds ratio =1.80, 95% confidence interval (CI) =0.21-3.28].The mean effect size of NS supplementation in respiratory diseases was 1.25, and Cohen's d (95% CI) ranged from 0.25 to 2.24.As a result, sufficient evidence was found to conclude that the intervention had a positive effect on the experimental group (z=2.46,p=0.01).In people with COVID-19, the group receiving NS supplementation had a higher recovery rate and a lower hospitalization rate.Fewer patients were infected in the group that received NS supplements for protection against COVID-19.Adverse effects reported include insomnia, daytime lethargy (when administered orally), excessive nasal dryness, stomach upset, and headache.There was insufficient evidence that prophylactic use of NS has a positive effect for COVID-19 or respiratory diseases.