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Daily cinnamon supplements may help lower blood sugar in prediabetes. Image credit: Jacob Maentz/Getty Images.
  • Cinnamon, a spice from the inner bark of trees from the genus Cinnamomum, is widely used in cooking.
  • It is also taken as a food supplement, with health benefits that may include antioxidant, anti-inflammatory and antidiabetic effects.
  • Adding to the evidence for potential antidiabetic effects, a new study has found that a 4-week course of cinnamon supplements reduced blood glucose (sugar) levels in people with obesity or overweight and prediabetes.

Cinnamon has been used since around 2800 Before the Common Era (BCE) as a flavoring, an anointing oil and for medicinal purposes. The Romans used it to treat digestive and respiratory ailments, and the ancient Egyptians used it for fragrance and flavoring.

More recently, the health benefits of cinnamon have been widely investigated. Studies suggest that the spice may have antioxidant, anti-inflammatory, antidiabetic, antimicrobial and even anticancer effects.

Now, in a double-blind crossover study, researchers have found that cinnamon supplements could help to reduce blood glucose (sugar) levels in people with obesity or overweight and prediabetes.

The findings are published in The American Journal of Clinical Nutrition.

Kelsey Costa, a registered dietitian nutritionist and nutrition consultant for Diabetes Strong, not involved in this study, commented on its methods for Medical News Today. She told us:

“While the study’s cohort was chosen to explore the effects of cinnamon on glucose regulation in individuals with prediabetes and obesity, its applicability to a broader demographic requires caution. The small sample size limits the robustness of the conclusions and reflects the need for larger, more representative studies.”

“However,” Costa added, “this research utilizes continuous glucose monitoring (CGM), which adds a novel and more precise dimension to our understanding of cinnamon’s impact on blood sugar levels.”

Previous studies into the effect of cinnamon on blood glucose levels have shown inconsistent findings, although a 2023 umbrella meta-analysis did find that cinnamon supplements reduced fasting blood glucose.

The researchers recruited 18 people with overweight or obesity — mean body mass index (BMI) of 31.5 — and prediabetes — a condition where blood glucose levels are consistently high, which can lead to type 2 diabetes — for a 4-week randomized, double-blind crossover trial of cinnamon supplementation.

First, they put the participants on a 2-week, low polyphenol “beige“ diet — a type of diet rich in simple carbohydrates — and told them to avoid any foods containing cinnamon. They then divided the participants randomly into a treatment group and a placebo group.

They gave each group 16 visually identical capsules per day, 8 to be taken with breakfast and 8 with dinner. The treatment group capsules contained a total of 4 grams (g) of cinnamon, while each placebo capsule contained only maltodextrin (250 milligrams), making a total of 4 g maltodextrin daily.

The researchers told the participants to continue their diet, and take the capsules as instructed for 4 weeks.

After 4 weeks, the groups did a 2-week “washout“ phase when they took no capsules, before swapping groups. Neither the participants nor the researchers knew who was receiving cinnamon and who was receiving placebo.

Both Costa and Dr. Menka Gupta, functional medicine doctor at Nutra Nourish, neither of whom were involved in the study, expressed concern about the use of maltodextrin as placebo.

Dr. Gupta commented: “Maltodextrin has been shown to increase blood glucose due to its high glycemic index. This could have potentially accentuated the difference between the cinnamon and placebo groups.”

Costa explained: “Typically, maltodextrin is used in placebo-controlled studies due to its neutral flavor and similarity in appearance to the supplement being tested; however, given that maltodextrin can cause a glycemic response due to the body’s rapid conversion of it to glucose, there could be a concern that its utilization might have confounded the study’s results.”

“To ensure the validity and reliability of the outcomes, future research could benefit from selecting a non-glycemic placebo or transparently accounting for the potential effects of maltodextrin in the study’s analysis and discussion,” she advised.

We reached out to the authors for comment, but they did not respond to our request in time for publication.

The researchers monitored the participants’ blood glucose levels using a continuous glucose monitoring device fixed to the upper arm, which measured glucose levels every 15 minutes.

In addition, at 4 time points in the study — after the 2-week introductory diet, after the first 4-week trial, after washout, and after the second 4-week trial — the participants gave blood samples for an oral glucose tolerance test (OGTT).

Researchers took blood samples after participants had fasted for 8–12 hours, then gave them 75 g of glucose cola to drink, plus 8 capsules of cinnamon or placebo. They took further blood samples every 30 minutes for 3 hours.

Continuous glucose monitoring showed that participants taking cinnamon had consistently lower levels of blood glucose, and lower glucose peaks than those on placebo. However, there was no difference in the OGTT between the two groups.

The researchers suggest this is because continuous monitoring is a more sensitive measure of glucose changes.

“The significant decrease in blood glucose levels seen with a 4g daily intake of cinnamon could be attributed to its rich polyphenol content and diverse bioactive compounds, which include cinnamaldehyde, proanthocyanidins, catechins, coumarin, trans-cinnamic acid, and various flavonoids. […] These natural compounds boost insulin’s ability to connect with cells, prompting them to take in glucose more effectively. They also reduce harmful inflammation and support the liver in storing excess glucose as glycogen for future energy needs.”

– Kelsey Costa

The researchers also propose that the impact of cinnamon on the gut microbiome — encouraging growth of beneficial bacteria while inhibiting growth of others — may affect blood glucose.

Dr. Gupta agreed.

“Cinnamon could improve gut health: Beneficial bacteria like Lactobacillus and Bifidobacterium can enhance gut barrier function, reducing systemic inflammation. Lower inflammation is associated with improved insulin sensitivity,” she explained.

“Beneficial bacteria ferment dietary fibers to produce short-chain fatty acids, such as butyrate, acetate, and propionate, which can improve glucose metabolism by enhancing insulin sensitivity and regulating energy expenditure and storage,” she added.

Dr. Gupta advised that cinnamon might have a role to play in managing prediabetes. “Adding cinnamon to the diet can blunt the blood glucose increase and can be beneficial part of a balanced diet for people with prediabetes,” she said.

“However,” she cautioned, “cinnamon contains coumarin, which can be toxic at high levels.”

Costa recommended other evidence-based measures to help control prediabetes: “Embracing diets rich in healthy plant-based foods, engaging in guided intermittent fasting, and practicing intuitive and mindful eating can improve nutrition while enhancing overall metabolic health.”

“Weight loss achieved by combining a healthy, reduced-calorie diet with regular exercise has been shown to be twice as effective as weight loss achieved through diet alone in reversing prediabetic states. Moreover, reducing abdominal fat is essential due to its strong association with insulin resistance,” added Costa.

Both advised that you should always consult a health professional before taking supplements or making lifestyle changes.