A crossover randomized controlled trial examining the effects of black seed (Nigella sativa) supplementation on IL-1β, IL-6 and leptin, and insulin parameters in overweight and obese women

Background: Nigella sativa (NS) oil has been found to have advantageous benefits in the management of inflammation and obesity. This study investigated the effect of NS supplementation on blood mRNA expressions and serum levels of IL-1β, IL-6, leptin, and insulin concentrations in overweight/obese women. Methods: In a crossover design, participants were randomized to receive either NS supplements(2000 mg/day) or placebo for 2 durations(8 weeks). With between-subject and within-subject components and interactions, a repeated-measure ANOVA model was used considering the treatment, time, and the carryover effects. Cohen’s d(d) was used to measure the magnitude of the effects. Results: Forty-six eligible participants were included. NS supplementation significantly reduced the mRNA expressions(d=-0.68, P = 0.03) and serum levels of IL-1β with medium-high effect sizes(d=-1.6, P < 0.001). Significant reductions with large effect sizes were observed in the gene expression and serum levels of IL-6(d=-1.8, d=-0.78, respectively; P < 0.01) and Leptin(d=-1.9, d=-0.89, respectively; P < 0.01, serum leptin P carryover < 0.001). Despite the meaningful carryover effect for serum leptin, results remained significant following the first intervention period analysis(P < 0.001). A significant but low effect size decrease in serum insulin was observed(d=-0.3, P = 0.02). Conclusions: The clinical significance of present findings regarding improvements in obesity-related pro-inflammatory markers must be interpreted with caution due to some observed medium-low effect sizes. Trial registration: IRCT20180430039475N1 (Date:25/6/2018).