Daily supplementation with 1,500 mg of curcumin extract reduced fasting blood glucose, lowered hemoglobin A1c, and improved pancreatic β-cell function in obese people with type 2 diabetes.
Those are the topline findings from a recent, year-long, placebo-controlled trial, involving 229 participants. Curcumin-treated patients also got a small but significant bonus benefit: weight loss.
“We believe that curcumin intervention in type 2 diabetes patient with obesity can improve the metabolic and obesity parameters by reduced insulin resistance level, and have anti-inflammatory effect by maintaining healthy β-cell functions,” writes lead investigator Metha Yaikwawong, of the Department of Pharmacology, Siriraj Hospital, Bangkok, Thailand.
“Because inflammation is one of the main causes of β-cell degradation, we hypothesize that the anti-inflammation activity and body weight regulation of curcumin are key factors for the antidiabetic property.”
Working with researchers and clinicians at the Princess Maha Chakri Sirindhorn Medical Center of Srinakharinwirot University, Dr. Yaikwawong enrolled 275 men and women who met the 2017 American Diabetes Association’s criteria for Type 2 Diabetes: a fasting plasma glucose (FPG) ≥ 126 mg/dL; oral glucose tolerance test (OGTT at 2 h) ≥ 200 mg/dL; glycated hemoglobin (HbA1c) ≥ 6.5%; random plasma glucose ≥ 200 mg/dL; along with the classic symptoms of hyperglycemia.
They excluded people with type 1 diabetes, impaired glucose tolerance, maturity onset diabetes of youth, or gestational diabetes.
Most subjects were overweight or obese, with the mean baseline BMI being 26.7 and 27.2 kg/m2 in the placebo and curcumin groups, respectively. Well over half were hypertensive, and roughly three-quarters were dyslipidemic. Those already on BP-regulating (calcium channel blockers, beta blockers, angiotensin blockers) or lipid-modifying drugs (statins) remained on their regimens for the 12-month duration of the study.
All were on metformin, which they also continued throughout the study. No other glucose-modifying drugs were permitted. Likewise, the researchers disallowed dose adjustments to or cessations of any of the pharmaceutical regimens.
The participants were randomly assigned to placebo or to 1,500 mg per day (6 capsules) of curcumin taken in thrice-daily doses. The curcumin rhizomes came from the Kanchanaburi province of Thailand. The rhizomes were ground into powder, then ethanol-extracted. Each capsule contained 250 mg of curcuminoids.
At baseline, the investigators measured body weight, BMI, fasting plasma glucose, Hb A1c, β-cell function (using the homeostasis model assessment [HOMA-β]), insulin resistance (HOMA-IR), plasma insulin, adiponectin, and leptin. They repeated all these measurements at 3-, 6-, 9-, and 12-months.
A total of 229 participants completed the year-long study and all the follow-up visits.
Significant Metabolic Benefits
After 12 months of treatment, the curcumin-treated group showed significant reductions in fasting blood glucose, while in the placebo group the FBG numbers tended to rise (115.49 mg/dL vs.130.71 mg/dL; P < 0.05).
The glucose changes were accompanied by lower HbA1c measurements among the curcumin-treated people, but not in those on placebo (mean of 6.12 vs. 6.47; P < 0.05).
Higher HOMA-β (136.20 vs. 105.19; P < 0.01) in the curcumin group points to better overall β-cell function, say Yaikwawong and colleagues. Concurrently, the curcumin-treated group showed a lower level of HOMA-IR (4.86 vs. 6.04; P < 0.001), and higher levels of adiponectin (14.51 vs. 10.36; P < 0.001) when compared to the placebo group (Yaikwawong M, et al. Nutrition Journal. Oct 2024).
In short, daily curcumin supplementation seemed to shift glucose metabolism in an overall healthier direction. And this translated into measurable changes in weight and body composition: BMI was significantly lower in the curcumin versus the placebo groups at 12 months (25.94 vs 29.34 kg/m2), with a P value of 0.001.
On average, the curcumin-treated patients lost weight over the 12-month trial period. The mean body weight in the treatment group went from 69.9 kg at baseline (range 71-120 kg) to 66.1 kg (range 68-114) at 12 months. There was no such trend observed in the placebo group. The curcumin group also showed lower mean leptin levels (9.42 vs. 20.66; P < 0.001), suggesting that the herb may have an appetite-regulating effect.
“A 12-month curcumin intervention in type 2 diabetes patients shows a significant glucose-lowering effect. Curcumin treatment appeared to improve the overall function of β-cells and reduce both insulin resistance and body weight, with very minor adverse effects.”
–Metha Yaikwawong,
The authors contend that the metabolic changes they saw in association with curcumin supplementation are indeed effects of bioactive compounds within the plant, and not the result of any dietary or lifestyle changes.
They note that “Before the study, all subjects were….advised to consume low-glycemic index foods, such as legumes and whole grains, increase dietary fiber intake, engage in at least 150 min of moderate-intensity aerobic exercise per week, and maintain consistent physical activity.” There were no major differences between the two groups in their adherence to these recommendations.
Safe and Well-Tolerated
Dr. Yaikwawong and his team found few adverse effects associated with daily high-dose curcumin supplementation. There were some incidents of mild abdominal pain (12%), diarrhea (8%), and headaches (4%) in the curcumin group. But these were infrequent and inconsequential. None of the patients discontinued treatment due to side effects.
The researchers monitored Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), and creatinine throughout the 12-month period and saw no significant differences between the curcumin and placebo group, indicating that the curcumin had no detrimental hepatic effects. Neither was there any evidence of an overtreatment effect: none of the curcumin-treated groups showed symptoms of hypoglycemia.
Strengthening Curcumin’s Case
This is not the first study to suggest that curcumin supplementation leads to favorable glucose metabolism and that it could have a role to play in treatment of diabetes and cardiometabolic disease. Yaikwawong’s group previously showed that a curcumin intervention could avert the progression from pre-diabetes to Type 2, and that it could improve β-cell function and increase insulin sensitivity (Chuengsamarn S, et al. J Nutr Biochem. 2014. Chuengsamarn S, et al. Diabetes Care. 2012).
Those earlier clinical trials built on several pre-clinical studies suggesting that compounds within turmeric could reduce insulin resistance.
Several other research teams worldwide have also looked at the potential of curcumin in the context of metabolic disorders. There are three published trials suggesting that compounds from this unique rhizome have antidiabetic effects. However, these studies are small (less than 100 patients) and of short duration (3 months).
The new study is by far the largest, longest, and most thorough. The results strengthen the case for using curcumin in the care of people with metabolic syndrome, T2D, and obesity.
“A 12-month curcumin intervention in type 2 diabetes patients shows a significant glucose-lowering effect. Curcumin treatment appeared to improve the overall function of β-cells and reduce both insulin resistance and body weight, with very minor adverse effects,” wrote Yaikwawong and his colleagues. “Curcumin intervention in obese patients with type 2 diabetes may be beneficial.”
Benefits Beyond Rx Drugs
The authors underscore the significant positive correlation between changes in body weight and HbA1c levels in the curcumin-treated group, that curcumin treatment may be able to improve β-cell function in type 2 diabetes patients.
Given that all of the patients in this study were already on metformin, and many were also taking antihypertensive and lipid-regulating drugs, the data suggest curcumin could potentially improve upon the benefits obtained with prescription drugs.
Yaikwawong acknowledges that the advent of the GLP-1 agonists has transformed the clinical care of people with diabetes, obesity, and other related metabolic problems. But the potential long-term adverse effects of these drugs, and their high cost, render them less-than-optimal for a lot of people.
Whether or not curcumin alone could deliver drug-like metabolic effects would need to be the subject of future clinical studies, and the Thai researchers are not suggesting that curcumin be used as a substitute for prescription products. But the data so far do suggest that this venerable culinary herb can affect beneficial metabolic changes without adverse consequences.
The biggest drawback to the regimen tested by Yaikwawong and colleagues is its complexity. Six capsules of curcumin taken in three separate doses over the course of a day is not exactly user-friendly. One would expect that in a real-world setting, compliance would likely decline rapidly over time.
The authors acknowledge that their current study was not designed to study dose-response relationships. It remains to be seen whether people could obtain similar metabolic benefits from lower doses or less onerous regimens.
That said, the Yaikwawong study is a big win for fans of curcumin. It adds glycemic regulation to the growing list of potential curcumin benefits that already includes mitigation of dyspepsia, improvement of lipid profiles, regulation of inflammation, potential anti-cancer effects, and an anti-depressant effect comparable to fluoxetine.
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