Type 2 diabetes mellitus (T2DM) is one of the most prevalent diseases globally. Dyslipidemia, a risk factor for cardiovascular disease, is common in patients with diabetes. Characteristics of dyslipidemia include increased serum triglyceride (TG) and low-density lipoprotein cholesterol (LDL-c) and decreased high-density lipoprotein cholesterol (HDL-c). Turmeric (Curcuma longa, Zingiberaceae) rhizome has been shown to have antioxidant and anti-inflammatory properties, which may benefit chronic conditions including diabetes. In animals, turmeric is reported to reduce blood glucose and lipids, improve insulin resistance, and aid weight loss in obese mice. This randomized, double-blind clinical trial was conducted to determine the effects of powdered turmeric on glycemic status, lipid profile, high sensitivity C-reactive protein (hs-CRP, a marker of chronic inflammation), and total antioxidant capacity in patients with T2DM and dyslipidemia.
Patients diagnosed with T2DM were recruited from the Endocrinology and Metabolism Research Center in Firoozgar Hospital of Iran University of Medical Sciences. Eligible patients were 30 to 70 years old with a fasting blood glucose < 200 mg/dL, hemoglobin A1c (HbA1c) > 6%, TG > 150 mg/dL, or LDL-c > 100 mg/dL, a body mass index (BMI) between 20 and 35 kg/m2, and no use of insulin therapy. Exclusion criteria included use of antioxidants, multivitamins, or polyphenol supplements within three months, fasting blood glucose > 200 mg/dL or LDL-c > 160 mg/dL, serious heart, liver, kidney, or gastrointestinal diseases, thyroid disease, pregnancy or lactation, and change of diet, activity, or medication during the study.
Patients recruited were randomized by block randomization (block size 4) into the turmeric or placebo group. The turmeric group received 2,100 mg per day of powdered turmeric, which was locally purchased and ground, in three 700 mg capsules. The placebo received 2,100 mg per day of corn starch (Zea mays, Poaceae) in 700 mg capsules of similar shape and color. Both groups were instructed to take one capsule three times a day after each meal for eight weeks. Compliance was measured by counting leftover capsules, with > 80% compliance required. The patients were asked to maintain their usual diet and physical activity during the intervention period and to report any changes in medications. A 24-hr recall questionnaire and a two-day food diary were collected. Physical activity was evaluated using the International Physical Activity Questionnaire (IPAQ).
Bodyweight and height were measured, and BMI was calculated. Blood samples were collected after a 12-hr fast at the beginning and end of the study. Measured values included fasting blood glucose, HbA1c, TG, HDL-c, LDL-c, total cholesterol, and insulin. The HOMA-IR insulin resistance index was calculated from glucose and insulin levels. Additionally, apolipoproteins A1 and B, hs-CRP, and total antioxidant capacity were measured.
Eighty patients were recruited and randomly assigned to the turmeric (n=40) or the placebo (n=40) groups. Five patients were excluded due to changes in medication or use of insulin therapy (2), travel (1), and unwillingness to cooperate (2). Seventy-five patients were included in the final analysis (turmeric, n=39; placebo, n=36). There were no significant differences between the groups at baseline. Bodyweight was significantly reduced during the study in the turmeric group compared to the placebo group by a mean of 1.80 kg; P<0.001), although between-group differences in body weight were not significant either at baseline or at the study end. BMI decreased in the turmeric group (P=0.001), and the mean difference of BMI (between-group difference in change during the study) was also significant (P<0.0001). Fasting plasma glucose, insulin, and HOMA-IR declined slightly in the turmeric group and increased in the placebo group, but the changes and differences were not statistically significant. Mean HbA1c increased significantly in the placebo group (P=0.03) and minutely decreased in the turmeric group; the difference in change between the two groups was almost significant (P=0.07).
TG decreased significantly in the turmeric group (P<0.001); total cholesterol did not change significantly. Both TG and total cholesterol significantly increased in the placebo group (P=0.006 and P=0.001, respectively). The mean differences between TG and total cholesterol between groups were significant (P<0.001 and P=0.004, respectively). Decreases were observed in HDL-c in both groups; however, a significant decrease was observed only in the placebo group (P=0.02). Although final mean values were different between groups (P=0.02), the mean difference for HDL-c was not significant. LDL-c decreased significantly in the turmeric group compared with baseline (P=0.009), but the mean difference was not quite significant (P=0.050). Apolipoprotein A1 increased significantly in the placebo group (P=0.02). There were no significant changes in apolipoprotein B, hs-CRP, or total antioxidant capacity.
This study reports that daily consumption of 2,100 mg of turmeric powder for eight weeks significantly reduced body weight and BMI in patients with T2DM. Turmeric also caused significant reductions in TG and LDL-c but had no effect on glycemic status, hs-CRP, or total antioxidant capacity. The authors conclude that daily consumption of 2,100 mg of turmeric may reduce body weight, atherosclerosis, and complications from diabetes in patients with T2DM. However, only surrogate endpoints were measured in this short-term study, so it is unclear whether long-term benefits would be significant. The authors acknowledge that longer studies involving more patients should be done. They also suggest that a trial should be done to compare turmeric to isolated curcumin, a primary active ingredient in turmeric.
The authors declare no conflict of interest.
Peer Review Comment
The majority of the participants were already on drugs that affect the parameters the researchers were studying. Everyone in both groups was taking a blood sugar-lowering agent. Everyone in both groups was also taking a blood-lipid lowering agent. These are big confounding factors. Therefore, the takeaway should not be turmeric’s mild effects on lipids and no effect on measures of glucose, etc., but that turmeric TAKEN WITH prescription drugs already targeting these activities may provide additional benefits.
Adab Z, Eghtesadi S, Vafa MR, et al. Effect of turmeric on glycemic status, lipid profile, hs-CRP, and total antioxidant capacity in hyperlipidemic type 2 diabetes mellitus patients. Phytother Res. April 2019;33(4):1173-1181. DOI: 10.1002/ptr.6312.