The effect of sumac (Rhus coriaria L.) supplementation on glycemic indices: A systematic review and meta-analysis of controlled clinical trials.

BACKGROUND & AIMS: Rhus coriaria L. (Sumac) is a popular spice/herb with several biological functions owing to its antioxidant and insulin-like activities. Many clinical trials have indicated the potent anti-diabetic property of sumac but the results on few glycemic indices were inconclusive. Hence, this systematic review and meta-analysis were aimed to investigate sumac supplementation effect on glycemic indices. METHODS: Systematically searched was performed by two independent reviewers using online databases including: PubMed, Scopus, web of science, EMBASE from inception until November 2020. Data were pooled using a random-effects model and weighted mean difference (WMD) with 95 % confidence intervals (CI). RESULTS: A total of 6 potentially relevant clinical trials met the inclusion criteria with total of 278 participants. Random-effects meta-analysis suggested no significant effects on the levels of fasting blood glucose [-7.08 mg/dl, 95 % CI: -14.85 to 0.70,P = 0.07, I2 = 59.8 %], glycosylated hemoglobin (HbA1c) [-0.48 %, 95 % CI: -1.01 to -0.04, P = 0.07, I2 = 0.0 %], homeostatic model assessment for insulin resistance (HOMA-IR) [-0.97, 95 % CI: -1.96 to 0.02, P = 0.05, I2 = 83.8 %], and insulin [-2.94 Hedges' g, 95 % CI: -6.67 to 0.80, P = 0.12, I2 = 83.1 %] following supplementation with sumac powder. CONCLUSION: This meta-analysis showed no significant effects on any glycemic indices following supplementation with sumac powder.

Effect of Nigella sativa L. supplementation on inflammatory and oxidative stress indicators: A systematic review and meta-analysis of controlled clinical trials.

AIMS: The objective of the present study was to perform a systematic review and meta-analysis on randomized controlled trials (RCTs) assessing the effects of Nigella sativa L. supplementation on the circulating inflammatory and oxidative stress markers, including C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), total antioxidant capacity (TAC) and malondialdehyde (MDA). METHODS: Systematic search was performed up to March 2020 using PubMed, Scopus, and ISI web of science databases. Two reviewers independently assessed study eligibility, extracted data, and evaluated methodological quality of included primary studies. Statistical heterogeneity was assessed using I-square (I2) statistic. Data were pooled by using the random-effect model and standardized mean difference (SMD) was considered as the summary effect size. RESULTS: Twelve trials were identified to be suitable for our meta-analysis. The pooled results using random effects model indicated that Nigella sativa supplementation significantly reduced CRP (SMD: -0.35; 95% CI: -0.59, -0.12, P < 0.001, I2 = 10.5%) and MDA concentrations (SMD: -0.56; 95% CI: -0.98, -0.15, P < 0.001, I2 = 64.7%). Moreover, Nigella sativa supplementation increased TAC (SMD: 0.48; 95% CI: 0.09, 0.87, P = 0.01, I2 = 65.6%) levels; however, it did not affect TNF-α (SMD: -0.35; 95% CI: -0.70, 0.01, P = 0.05, I2 = 58.2%). CONCLUSION: Nigella sativa supplementation is associated with improved inflammation and oxidative status. Additional prospective studies are recommended using higher supplementation doses and longer intervention period.