A Systematic Review of the Potential Effects of Nigella sativa on Rheumatoid Arthritis

Considering the different untoward effects of the drugs prescribed for the treatment of rheumatoid arthritis (RA), there has been an increasing interest in adjuvant therapies devoid of such unfavorable reactions. Although the beneficial effects of Nigella sativa (N. sativa) on RA have been established, it seems that its mechanisms of action have not still been reviewed. The present review is designed to evaluate the effects of N. sativa on RA systematically. We searched these electronic databases until April 2019: PubMed, Scopus, ISI Web of Science, Cochrane Library, Embase, Ovid, ProQuest, and Google scholar. No restriction was conducted based on language or publication date. We selected all of the related clinical, animal, and in vitro studies. Review papers, abstracts in conferences, book chapters, and papers regarding the effects of N. sativa combined with other herbs, as well as articles regarding the effects of N. sativa on other diseases, were excluded. Each article was assessed critically for the possible risk of bias. Nineteen articles were reviewed. Animal and in vitro investigations supported the favorable effects of N. sativa on clinical, inflammatory, oxidative, and immunologic parameters on RA, whereas results of limited clinical studies did not illustrate any change or improvement of inflammatory and oxidative biomarkers in RA. N. sativa could control RA via multiple ways such as decreasing inflammation, inhibiting oxidative stress, and modulating the immune system. This paper provides persuasive clues to defend the efficacy of N. sativa in RA and justifies the significance of subsequent clinical trials.