Nigella sativa and health outcomes: An overview of systematic reviews and meta-analyses

Abstract

BackgroundNigella sativa (N. sativa) consumption has been associated with various health outcomes; however, the results are not completely consistent.ObjectivesThis overview of systematic reviews and meta-analyses aimed to evaluate the reporting and methodological quality, and to grade the available evidence of associations between N. sativa and health outcomes.MethodsPubMed, Cochrane Library, Embase, and Scopus databases were searched from their inception to September 30, 2022. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2009 statement, Assessment of Multiple Systematic Reviews (AMSTAR) 2 checklist, and Grades of Recommendations, Assessment, Development and Evaluations (GRADE) systems were used to assess the reporting, methodological, and evidence quality for each meta-analysis, respectively. The results were synthesized in a narrative form.ResultsThis overview included 20 eligible meta-analyses published in peer-reviewed journals between 2013 and 2021. The overall methodological quality was relatively poor, with only one moderate quality, four low quality, and 15 critically low quality studies. For reporting quality, items two, five, eight, nine, 15, and 24 need to improve. Among the 110 outcome indicators of the quality of evidence, five were graded as moderate, 17 as low, and 88 as very low. Risk of bias, inconsistency, and imprecision were the main downgrading factors.ConclusionThis overview suggests that N. sativa is beneficial for various clinical outcomes. However, there are certain limitations to reporting and methodological quality. The clinical efficacy of N. sativa requires confirmation in high-quality, large-sample, randomized controlled trials.

Variation in the Composition and Quality of Nigella sativa L. Seed Oils—The Underestimated Impact on Possible Health-Promoting Properties

“…Currently, in the online database “ ”, there are 31 clinical studies on N. sativa L. with the status “completed” (25 studies) and the status “recruiting” (six studies)—access date: 25 July 2023. These clinical and other animal-based studies confirmed the analgesic; anticancer; antidiabetic; anti-inflammatory; antimicrobial; antioxidant; antitussive; broncho-dilating; gastro-, hepato-, and neuroprotective; immunomodulatory; and spasmolytic effects of the N. sativa L. oil [ 3 , 6 , 10 , 11 ].…”

Exploring the short-term influence of a proprietary oil extract of black cumin (Nigella sativa) on non-restorative sleep: a randomized, double-blinded, placebo-controlled actigraphy study

“…Black cumin seeds, powder, paste and oils have been traditionally used since ancient times for the treatment of various diseases such as cardiovascular, respiratory, rheumatism, headache, back pain, anorexia, amenorrhea, mental illness, eczema and hypertension. A number of phytochemicals including thymoquinone, thymohydroquinone, thymol, carvacrol, p-cymene, nigellidine, saponins, and flavonoids have also been identified in black cumin (25,26). Black cumin oil and its major bioactive component, thymoquinone, have been found to possess anti-inflammatory, antiarthritic, anti-allergic, anti-microbial, anti-diabetic, hypolipidemic, hepatoprotective, neuroprotective, and anticancer properties (27)(28)(29).…”

Potential Benefit of Spices for Glycemic Control

“…Statistically significant decreases in FBG and HbA 1c levels [83][84][85][86][87][88][89] were observed for subjects administered black seed, compared with controls (Table 2). When subgroup analyses were conducted, decreases in FBG were greater for those subjects with T2DM compared with the response to black seed among all patients.…”