The effect of sumac supplementation on insulin resistance, inflammation, oxidative stress, and antioxidant capacity in adults with metabolic syndrome: A randomized crossover clinical trial

The impact of sumac supplementation was not previously examined in patients with metabolic syndrome (MetS). So, we investigated the influence of sumac supplementation on insulin resistance, inflammation, oxidative stress, and antioxidant markers in adults with MetS. The current study was a single-center, triple-blind, randomized, placebo-controlled crossover clinical trial that was conducted on 47 patients with MetS. Participants were randomly divided into two groups of intervention and control in the first phase. They received capsules containing 500 mg sumac or placebo (lactose) twice a day, after lunch and dinner, for 6 weeks. After a 2-week washout period, the subjects crossed over to the alternate arm. In both arms, fasting venous blood samples were obtained at baseline and at the sixth week of the intervention to determine glycemic status, high-sensitivity C-reactive protein (hs-CRP), malondialdehyde (MDA), total antioxidant capacity (TAC), and antioxidant enzymes activity. The mean (+/- SD) age, weight, and body mass index of participants were respectively 58.7 +/- 5.83 years, 79.9 +/- 14.35 kg, and 31.6 +/- 4.6 kg/m(2); 80.9% of subjects were females (n = 38). Based on per-protocol analyses, the serum fasting insulin concentration was unexpectedly decreased in the placebo group (change in sumac vs. control: 0.95 +/- 3.9 vs. -1.17 +/- 3.9 mU/L; p = 0.04). Sumac supplementation, compared to control, has marginally enhanced catalase activity (change in sumac vs. control: 2.91 +/- 9.5 vs. -1.07 +/- 9.1 nmol/min/ml; p = 0.06). This supplementation has also increased serum TAC and the activity of superoxide dismutase, but these changes were not significant. This intervention did not affect other insulin resistance, inflammatory, or oxidative stress markers. We found that 1 g/day sumac consumption for 6 weeks, as adjuvant therapy, could improve the antioxidant defense system in adults with MetS but did not affect insulin resistance, inflammation, or oxidative stress.