Benefits
Blood sugar and HbA1c markers in placebo-controlled trials
In 41 adults with type 2 diabetes, 3 g a day of sumac powder for 3 months lowered HbA1c (6.75% to 6.18%) and fasting glucose more than placebo, though the groups started with different HbA1c values. A 2 g trial in fatty liver also found lower glucose and HbA1c. A 6-week crossover trial and an 8-week trial found no glucose difference.
Blood cholesterol, triglyceride and HDL levels
In 72 adolescents with high blood fats, 1.5 g a day for 1 month lowered total cholesterol, LDL and triglycerides more than placebo. In 80 adults, 1 g a day for 6 weeks raised HDL and apolipoprotein A1 but did not change total cholesterol, LDL or triglycerides. A 3-arm trial in 105 dialysis patients found no lipid difference.
Systolic blood pressure in a 6-week crossover trial
In 47 adults with metabolic syndrome, 500 mg of sumac twice a day for 6 weeks lowered systolic pressure by about 5.6 mmHg versus a small rise on placebo, with no change in diastolic pressure, body measures, glucose or blood fats. A pooled analysis of 17 trial reports found lower diastolic but not systolic pressure.
Liver enzyme levels in placebo-controlled diet trials
In 80 adults with fatty liver on a reduced-calorie diet, 2 g a day of sumac powder for 12 weeks lowered the liver enzymes ALT and AST and a liver fibrosis measure more than placebo. A second trial in 45 adults with fatty liver, using 3 g a day for 8 weeks with a diet, found no difference from placebo in liver enzymes.
Body weight and waist size alongside a reduced-calorie diet
In 62 overweight women with mild to moderate depression on a reduced-calorie diet, 3 g a day of sumac for 12 weeks gave more loss of weight, BMI, body fat and waist size than placebo. Four other cited trials found no difference in body measures; a pooled analysis of 17 trial reports found about 1 kg lower body weight than control.
Antioxidant capacity and lipid oxidation markers in blood
In the 3-month type 2 diabetes trial, sumac raised total antioxidant capacity and paraoxonase 1 activity and lowered malondialdehyde, a marker of fat oxidation, versus placebo. The diet trial in women also found lower malondialdehyde. In a 6-week crossover trial these markers did not differ significantly from placebo.
Mechanism of action
Tannin and polyphenol rich fruit
Hydrolyzable tannins are the most prominent compound group in sumac fruit, followed by flavonoids and phenolic acids, and gallic acid was the most abundant phenolic acid in tested fractions. Fractions rich in tannins and anthocyanins showed strong antioxidant activity in lab tests, which is not the same as an effect in the body.
Gallic acid and glucose signaling in animal and cell studies
In animal experiments gallic acid raised signaling proteins tied to glucose uptake (pAkt, PPAR-gamma and GLUT4), and in cell studies it improved insulin sensitivity of fat cells. These are lab findings with an isolated compound; they suggest a possible route for the blood sugar results but have not been shown in people taking sumac.
Clinical trials
Double-blind, randomized, placebo-controlled trial in Iran in adults with type 2 diabetes who kept their usual medicines, reported in two papers: 3 g/day of sumac powder (six capsules, two with each meal) or lactose for 3 months. Funded by the Research Institute for Islamic and Complementary Medicine, Iran University of Medical Sciences. (Shidfar et al. 2014, Iran J Pharm Res)
41 adults with type 2 diabetes (22 sumac, 19 placebo), average age about 47.
HbA1c fell from 6.75% to 6.18% on sumac and was unchanged on placebo (7.30% to 7.31%); the groups started about half a point apart. Changes in fasting glucose, apolipoprotein B, apolipoprotein A-I and total antioxidant capacity also differed between groups. The companion paper (Rahideh et al. 2014, J Res Med Sci) reported between-group differences in insulin, HOMA-IR, malondialdehyde, hs-CRP and paraoxonase 1 activity.
Randomized, double-blind, placebo-controlled trial in Iran in adults with nonalcoholic fatty liver disease: 2,000 mg/day of sumac powder or placebo for 12 weeks, with a 500-calorie deficit diet in both groups. The abstract does not state a funding source or the size of each change. (Kazemi et al. 2020, Complement Ther Clin Pract)
84 adults with fatty liver (42 per group); 80 completed.
Compared with placebo, the sumac group had greater decreases in a hepatic fibrosis measure, the liver enzymes ALT and AST, fasting glucose, insulin, HbA1c, HOMA-IR, malondialdehyde and hs-CRP, and a higher insulin sensitivity index (QUICKI) (P < 0.05).
Double-blind, randomized, placebo-controlled trial in Iran in overweight or obese adults with nonalcoholic fatty liver disease: 3 g/day of sumac powder (six 500 mg capsules) or rice flour placebo for 8 weeks, both with a balanced 500-calorie deficit diet. Outcomes were weight, BMI, waist, body fat, blood lipids, fasting glucose, insulin, HOMA-IR, the liver enzymes AST and ALT, hs-CRP and malondialdehyde. Funded by Shiraz University of Medical Sciences. (Mohit et al. 2024, Avicenna J Phytomed)
45 overweight or obese adults (23 sumac, 22 placebo); 10 in each group did not finish, and the analysis was by intention to treat.
Several measures improved from baseline during the diet, but none of the body measures or blood tests differed significantly between sumac and placebo at the end. The authors called for larger and longer trials.
Two-arm, double-blind, placebo-controlled randomized trial in Shiraz, Iran, in adults with primary hyperlipidemia, registered as NCT02295293 (500 mg sumac powder capsule twice daily for 6 weeks; primary outcomes total cholesterol, triglycerides and HDL). Total cholesterol, LDL and triglycerides did not differ between groups. Sponsored by Shiraz University of Medical Sciences; an earlier conference abstract reported the same 80-patient trial. (Hajmohammadi et al. 2018, J Integr Med)
80 adults with primary hyperlipidemia (the ClinicalTrials.gov record lists 74 enrolled).
HDL cholesterol and apolipoprotein A1 rose more on sumac than on placebo (P = 0.001), and the HDL rise held after adjustment for age, sex, body size and smoking. The other two primary outcomes showed no difference (see study details).
Triple-blinded, randomized, placebo-controlled trial at the Isfahan Cardiovascular Research Center, Iran, in obese adolescents with dyslipidemia: 500 mg of powdered sumac fruit, standardized for phenolic content, or lactose, three times daily for 1 month. HDL did not change. A pharmacy doctoral thesis funded by Isfahan University of Medical Sciences. (Sabzghabaee et al. 2014, Med Arch)
72 obese adolescents aged 12 to 18 (36 per group).
Total cholesterol fell from 204 to 189 mg/dL, LDL from 123 to 102 mg/dL and triglycerides from 163 to 148 mg/dL on sumac, with little change on placebo; the between-group differences were significant for all three (P = 0.006, < 0.001 and 0.017). No significant side effects were reported.
Single-center, triple-blind, randomized, placebo-controlled crossover trial in Iran in adults with metabolic syndrome, reported in two papers: 500 mg sumac fruit powder or lactose twice daily for 6 weeks per phase with a 2-week washout. Fasting glucose and blood lipids did not differ between phases; the companion paper (Hajhashemy et al. 2023, Phytother Res) found no effect on insulin resistance, inflammation or oxidative stress markers, and fasting insulin fell more on placebo. Funded by Isfahan University of Medical Sciences. (Mirenayat et al. 2023, Nutr J)
47 adults, average age 58.7, about 81% women.
Systolic blood pressure fell by 5.6 mmHg on sumac versus a 0.8 mmHg rise on placebo (P = 0.004); diastolic pressure and body measures did not differ. No adverse effects were reported.
Randomized, double-blind, placebo-controlled trial in Iran in overweight or obese women with mild to moderate depression, all on a restricted-calorie diet: 3 g/day of sumac or placebo for 12 weeks. Registered as IRCT20131228015968N6 (2019), which lists body measures as primary outcomes and inflammation, oxidative stress, appetite hormones, glucose, insulin, blood lipids and depression as secondary outcomes; neither paper's abstract reports blood lipids. IL-6 and TNF-alpha fell only on sumac but not significantly, and hs-CRP and depression scores fell in both groups with no difference. Funded by the Faculty of Nutrition and Food Technology, Shahid Beheshti University of Medical Sciences. (Hariri et al. 2020, Phytother Res)
62 overweight or obese women aged 20 to 65 (60 in the 2023 report).
Compared with placebo, sumac reduced body weight, BMI, body fat, visceral fat, waist and hip size and malondialdehyde. A 2023 paper (Hariri et al. 2023, Complement Ther Clin Pract) reports secondary outcomes that this single registered protocol lists, in 60 women with the same senior author, population and regimen, so it appears to be a second report of the same trial, not an independent replication: appetite score, leptin, neuropeptide Y, insulin, fasting glucose and HOMA-IR were lower than on placebo.
Triple-blind, randomized, placebo-controlled 3-arm trial in western Iran in hemodialysis patients: sachets of 2 g or 3 g sumac fruit powder or wheat-powder placebo daily for 12 weeks. Outcomes were triglycerides, total cholesterol, LDL, HDL and BMI; none differed between groups over time (LDL P = 0.998), and LDL changed over time within every group, including placebo. Funded by Lorestan University of Medical Sciences. (Alahnoori et al. 2022, Evid Based Complement Alternat Med)
120 adults on hemodialysis (40 per group); 105 analyzed.
Neither sumac dose differed from placebo on any measured outcome. The authors kept doses at or below 3 g because earlier reports linked more than 5 g a day to digestive problems.