Effects of sumac supplementation on metabolic markers in adults with metabolic syndrome: a triple-blinded randomized placebo-controlled cross-over clinical trial.

BACKGROUND: Despite the prior evidence of the impacts of sumac on glycemic indices, lipid profile and visceral fat, there is a lack of evidence regarding the efficacy of sumac in cases with metabolic syndrome (MetS). Therefore, we aimed to assess the effect of sumac supplementation on MetS markers among adults with this syndrome. METHODS: In this triple-blinded randomized placebo-controlled cross-over clinical trial 47 adults with MetS were randomly assigned to receive 500 mg sumac or placebo (lactose) capsule, twice a day. Each phase took 6 weeks and there was a 2-week washout between phases. All clinical evaluations and laboratory tests were conducted before and after each phase. RESULTS: At the baseline of the study, mean (± SD) age, weight, and waist circumference of participants were respectively 58.7 (± 5.8) yr, 79.9 (± 14.3) kg, and 107.6 (± 10.8) cm. Intention to treat analysis (ITT) analyses revealed that sumac supplementation decreased systolic blood pressure by 5 mmHg (128.8 ± 21.4 at the baseline vs. 123.2 ± 17.6 after 6 weeks intervention, P = 0.001). The comparison of changes in two trial arms showed that sumac supplementation significantly reduced systolic blood pressure (sumac group -5.59 ± 10.6 vs. control group 0.76 ± 10.5, P = 0.004), but did not change anthropometric indices or diastolic blood pressure. Similar results were also found in the per-protocol analyses. CONCLUSIONS: This cross-over trial revealed that sumac supplementation could reduce systolic blood pressure in men and women with MetS. Daily intake of 1000 mg sumac, as an adjuvant therapy, may be beneficial in management of MetS in adults.

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/m2 ; 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.

Serum vitamin D levels in relation to metabolic syndrome: A systematic review and dose-response meta-analysis of epidemiologic studies.

Several epidemiological studies examined the association of serum vitamin D with metabolic syndrome (MetS), but the findings were inconsistent. We conducted a systematic review and dose-response meta-analysis to quantify the association between blood vitamin D levels and MetS in adults. A systematic search up to December 2020 was conducted in MEDLINE (PubMed), ISI (Web of Science), Scopus, and Google Scholar databases for epidemiological studies that assessed the relation of serum 25-hydroxyvitamin D (as the exposure) and MetS (as the outcome) in adults. Eligible cross-sectional studies were restricted to those with representative populations. Finally, 43 studies were included in the analysis (38 cross-sectional, one nested case-control, and four cohorts studies). Combining 41 effect sizes from 38 cross-sectional studies included 298,187 general adult population revealed that the highest level of serum vitamin D, compared with the lowest level, was significantly related to a 43% decreased odds of MetS in developed countries (odds ratio [OR]: 0.57; 95% confidence interval [CI]: 0.49-0.65) and 40% in developing countries (OR: 0.60; 95% CI: 0.52-0.70). Linear dose-response analysis (including 222,175 healthy individuals and 39,308 MetS patients) revealed that each 25 nmol/L increase in serum vitamin D level was significantly associated with a 15% decreased odds of MetS (OR: 0.85; 95% CI: 0.80-0.91); however, we found no significant nonlinear association. Meta-analysis of five prospective studies with 11,019 participants revealed no significant relation (relative risk [RR]: 0.70; 95% CI: 0.37-1.32). This meta-analysis indicated an inverse association between serum vitamin D concentrations and risk of MetS in general adult populations in cross-sectional studies in a dose-response manner. However, no significant association was found in a small number of cohorts. More prospective studies are needed to confirm the causality of this relationship.