Cinnamon improves glycaemic control in obese adults with prediabetes

Adding cinnamon spice, a substance rich in polyphenols, to daily diets may have beneficial glycaemic effects in adults with prediabetes, suggests a study.

“Cinnamon, a widely available and low-cost supplement, may contribute to better glucose control when added to the diet in people who have obesity-related prediabetes,” the investigators said.

Eighteen individuals with obesity and prediabetes (mean age 51.1 years, mean fasting plasma glucose 102.9 mg/dL) participated in a 10-week randomized, controlled, double-blind, crossover trial following a 2-week run-in period of maintaining a low polyphenol/fibre diet.

The investigators randomized participants to take cinnamon (4 g/d) or placebo for 4 weeks, followed by a 2-week washout period, and switched them to the other intervention for another 4 weeks. They measured glucose changes with continuous glucose monitoring.

Oral glucose testing was carried out immediately after ingestion of cinnamon or placebo at four time points to assess their acute effects both at the baseline and end of each intervention phase. The investigators obtained digestive symptom logs daily.

A total of 66,624 glucose observations were performed during 694 follow-up days. Cinnamon intake resulted in significantly lower 24-h glucose concentrations (mixed models; effect size [ES], 0.96, 95 percent confidence interval [CI], ‒2.9 to ‒1.5; p<0.001) when compared with placebo. [Am J Clin Nutr 2024;119:649-657]

Cinnamon administration similarly led to significantly lower mean net area under the curve (netAUC) for glucose versus placebo (over 24 h; ES, ‒0.66, 95 percent CI, 2,501.7‒5,412.1; p=0.01). Supplementation with cinnamon also generated lower glucose peaks relative to placebo (Δpeak, 9.56 mg/dL vs 11.73 mg/dL; ES, –0.57; 95 percent CI, 0.8‒3.7; p=0.027).

During oral glucose tolerance testing + cinnamon testing, glucose-dependent-insulinotropic-polypeptide concentrations increased (mixed-models; ES, 0.51, 95 percent CI, 1.56‒100.1; p=0.04), while triglyceride concentrations decreased (mixed-models; ES, 0.55, 95 percent CI, ‒16.0 to ‒1.6; p=0.02).

Both groups showed excellent treatment adherence (cinnamon: 97.6 percent; placebo: 97.9 percent; ES, ‒0.15, 95 percent CI, ‒1.8 to 0.2; p=0.5).

Additionally, digestive symptoms (eg, abdominal pain, borborygmi, bloating, excess flatus, and stools/day) did not significantly differ between cinnamon and placebo groups.

Polyphenols

“This glucose-lowering effect of cinnamon may be explained by unique compounds and high polyphenol content in cinnamon,” the investigators said.

“Cinnamon contains cinnamaldehyde, proanthocyanidins, coumarin, catechins, trans-cinnamic acid, and flavones,” they added. [Curr Cardiol Rep 2015;17:39; Evid Based Complement Alternat Med 2014;642942; Proc Nutr Soc 2008;67:48-53; Proc Nutr Soc 2008;67:48-53; Plant Foods Hum Nutr 2019;74:544-552; Nutrients 2022;14:2773]

Moreover, polyphenols improve insulin sensitivity by activating the insulin receptor through the following mechanisms: increased auto-phosphorylation of the insulin receptor, increased glucose transporter-4 receptor synthesis and activation, increased hepatic glycogen synthesis, and anti-inflammatory effects, which could be beneficial in diabetes. [Ann Fam Med 2013;11:452-459; J Med Food 2011;14:884-889; Cochrane Database Syst Rev 2012;9CD007170]

“However, the specific bioactive compounds in cinnamon responsible for these effects remain unknown,” the investigators said.