Ceylon cinnamon does not affect postprandial plasma glucose or insulin in subjects with impaired glucose tolerance

A Systematic Review Evaluating Cinnamon's Effects on Glucose Utilizing a Ranking System to Assess Bias and Study Quality

In the context of diabetes, the use of cinnamon continues to be among the most popular supplements taken by patients for glucose control. To strategically evaluate the available literature comparing various cinnamon species and statistically significant glucose effects after ranking studies based on two tools to assess bias and overall study quality, to clarify cinnamon's role in glucose control. The authors performed a systematic search based upon PRISMA guidelines. The search was conducted utilizing PubMed, AMED, CINAHL, EMBASE, Cochrane, and Medline databases, with the final search performed in September 2022 with restrictions to human subjects and English language. Electronic searches were conducted utilizing the keywords "diabetes mellitus" combined with Cinnamomum zeylanicum/Cinnamomum cassia/Cinnamomum verum combined with blood glucose (BG). A second search utilized "cinnamomum zeylanicum/cinnamomum cassia/cinnamomum verum" combined with "blood glucose," and a final search utilized "diabetes mellitus" combined with "cinnamon." Data extraction and ranking of included studies utilizing the risk of bias 2 tool and modified Heyland Methodological Quality Scoring tool were performed independently by two review authors. These authors compared their results and reconciled any differences in scoring to generate a final ranking of studies. A third author was available for any discrepancies that could not be resolved but was not needed. Forty-five studies were included in the review and were scored for bias and quality. Overall 62% demonstrated statistical significance for positive effects in at least one parameter around BG control. Applying the ranking systems reduced the percentage closer to 50%. Safety was extremely well documented across studies with few adverse effects. Results are limited by heterogeneity of glucose parameters, leading to studies being ranked individually and not synthesized. Cinnamon supplementation likely has a modest positive effect on BG. Based upon the strong safety profile, utilization of this spice as an adjunct to pharmacologic therapy is reasonable.

A Scoping Review of the Clinical Evidence for the Health Benefits of Culinary Doses of Herbs and Spices for the Prevention and Treatment of Metabolic Syndrome

Metabolic syndrome (MetS) is a growing global health problem. Evidence suggests that diets rich in phytochemical-containing herbs and spices can contribute to reducing the risk of chronic diseases. This review assesses the scope of evidence supporting the use of herbs and spices in the diet for the prevention or treatment of MetS and its associated health conditions. A search of the PubMed, Scopus and Google Scholar databases was carried out to assess the available clinical evidence for culinary doses of commonly used herbs and spices. Trials that were measuring health factors related to metabolic disorders in healthy individuals, or the health of individuals with MetS or associated diseases, were included. Out of a total of 1738 papers identified, there were 142 relevant studies on black pepper, chilli, cardamom, cinnamon, coriander, cumin, fennel, fenugreek, garlic, ginger, nigella seed, rosemary, sage and turmeric. No relevant research was found for cloves, mint, oregano, parsley or thyme. Cinnamon, fenugreek and ginger were the herbs/spices with the most published trials on them and that showed promise for glycaemic control. Cardamom appears to have potential to reduce inflammatory markers, and cinnamon, ginger and turmeric to reduce blood lipids. Patients with type 2 diabetes were the population most likely to be included in studies, but the preventative benefits of herbs/spices in healthy populations were also investigated, particularly for chilli, ginger and cinnamon. There is evidence for the beneficial effect of culinary doses of many common herbs/spices in the prevention and treatment of MetS and associated disorders.

Electrophilic Agonists Modulate the Transient Receptor Potential Ankyrin-1 Channels Mediated by Insulin and Glucagon-like Peptide-1 Secretion for Glucose Homeostasis

This pre-clinical study investigated the transient receptor potential ankyrin-1 (TRPA1) channels on modulating targets for glucose homeostasis using agonists: the electrophilic agonists, cinnamaldehyde (CIN) and allyl isothiocyanate (AITC), and the non-electrophilic agonist, carvacrol (CRV). A glucose tolerance test was performed on rats. CIN and AITC (5, 10 and 20 mg/kg) or CRV (25, 100, 300, and 600 mg/kg) were administered intraperitoneally (i.p.), and glycemia was measured. In the intestine, Glucagon-like peptide-1 (GLP-1) and disaccharidase activity were evaluated (in vivo and in vitro, respectively). Furthermore, in vivo and in vitro insulin secretion was determined. Islets were used to measure insulin secretion and calcium influx. CIN and AITC improved glucose tolerance and increased insulin secretion in vivo and in vitro. CRV was unable to reduce glycemia. Electrophilic agonists, CIN and AITC, inhibited disaccharidases and acted as secretagogues in the intestine by inducing GLP-1 release in vivo and in vitro and contributed to insulin secretion and glycemia. The effect of CIN on calcium influx in pancreatic islets (insulin secretion) involves voltage-dependent calcium channels and calcium from stores. TRPA1 triggers calcium influx and potentiates intracellular calcium release to induce insulin secretion, suggesting that electrophilic agonists mediate this signaling transduction for the control of glycemia.

Cinnamon as a Complementary Therapeutic Approach for Dysglycemia and Dyslipidemia Control in Type 2 Diabetes Mellitus and Its Molecular Mechanism of Action: A Review

The scientific evidence that cinnamon may exert beneficial effects on type 2 diabetes mellitus due to the biological activity of its bioactive compounds has been increasing in recent years. This review provides an overview of the effects of cinnamon on clinical parameters of diabetes and summarizes the molecular mechanisms of action of cinnamon on glucose and lipid metabolism. Search criteria include an electronic search using PubMed, Medline, and Cochrane Library databases. English literature references from 2000 up to 2022 were included. Following title and abstract review, full articles that met the inclusion criteria were included. The results from the available evidence revealed that cinnamon improved glycemic and lipidemic indicators. Clinical trials clarified that cinnamon also possesses an anti-inflammatory effect, which may act beneficially in diabetes. Based on in vitro and in vivo studies, cinnamon seems to elicit the regulation of glucose metabolism in tissues by insulin-mimetic effect and enzyme activity improvement. Furthermore, cinnamon seems to decrease cholesterol and fatty acid absorption in the gut. The current literature search showed a considerable number of studies on diabetic subjects. Some limitations in comparing published data should be highlighted, including variability in doses, extracts and species of cinnamon, administration forms, and antidiabetic therapy.

Effect of Aqueous Cinnamon Extract on the Postprandial Glycemia Levels in Patients with Type 2 Diabetes Mellitus: A Randomized Controlled Trial

Cinnamon is a spice used in traditional cuisine that has been investigated due to hypoglycemic properties. The objective of this study was to investigate the effect of aqueous cinnamon extract on postprandial glycemia levels in type 2 diabetes mellitus (DM2) adults. This clinical trial enrolled 36 adults with DM2, randomly allocated in two groups: the control group (n = 18) took only an oral glucose tolerance test (OGTT) and the intervention group (n = 18) took OGTT immediately followed by aqueous cinnamon extract (6 g/100 mL) ingestion. Blood glucose levels were measured on fasting and after 30, 60, 90 and 120 min in both groups. The chemical analysis of the aqueous cinnamon extract included total phenols content determination and antioxidant activity assessment through FRAP and DPPH methods. The data reveal that aqueous cinnamon extract ingestion did not show a significant difference in the incremental area under the curve (p = 0.834), maximum glucose concentration (p = 0.527) and glucose concentration variation (p = 0.873) compared with the control group. Cinnamon extract possess a total phenol content of 1554.9 mg/L gallic acid equivalent and a strong antioxidant capacity, revealed by the DPPH (5125.0 µmol Trolox/L) and FRAP (3658.8 µmol Trolox/L) tests. Aqueous cinnamon extract did not significantly influence postprandial glucose response in diabetic patients during an OGTT.

The effect of herbs and spices on risk factors for cardiometabolic diseases: a review of human clinical trials

Herbs and spices are recommended to increase flavor and displace salt in the diet. Accumulating evidence suggests herbs and spices may improve risk factors for cardiometabolic diseases. In this narrative review, an overview of evidence from human clinical trials examining the effect of herbs and spices on risk factors for cardiometabolic diseases is provided. Human clinical trials examining supplemental doses of individual spices and herbs, or the active compounds, have yielded some evidence showing improvements to lipid and lipoprotein levels, glycemic control, blood pressure, adiposity, inflammation, and oxidative stress. However, cautious interpretation is warranted because of methodological limitations and substantial between-trial heterogeneity in the findings. Evidence from acute studies suggests intake of mixed herbs and spices as part of a high-saturated fat, high-carbohydrate meal reduces postprandial metabolic impairments, including lipemia, oxidative stress, and endothelial dysfunction. Limited studies have examined the postprandial metabolic effects of incorporating mixed herbs and spices into healthy meals, and, to our knowledge, no trials have assessed the effect of longer-term intake of mixed herbs and spices on risk factors for cardiometabolic diseases. To inform evidence-based guidelines for intake of herbs and spices for general health and cardiometabolic disease risk reduction, rigorously conducted randomized controlled trials are needed, particularly trials examining herb and spice doses that can be incorporated into healthy dietary patterns.

Efficacy and safety of cinnamon in type 2 diabetes mellitus and pre-diabetes patients: A meta-analysis and meta-regression

INTRODUCTION

Cinnamon has been used as a dietary component and in the management of diabetes mellitus. This study systematically reviewed and synthesized evidence on the efficacy of cinnamon for the treatment of type 2 diabetes mellitus (T2DM) and pre-diabetes patients.

METHODS

Databases of Web of Sciences, the Cochrane library, PubMed, CINAHL and SCOPUS were searched. Stata version 13 (College Station, Texas 77845 USA) and RevMan var. 5.3 software were used for meta-analysis. Heterogeneity was assessed using Chi-square and I² tests.

RESULTS

Sixteen randomized controlled studies were included in the meta-analysis. Cinnamon significantly reduced fasting blood glucose (FBG) and homeostatic model assessment for insulin resistance (HOMA-IR) level compared to placebo with weighted mean difference (WMD) of -0.545 (95% CI: -0.910, -0.18) mmol/L, I² = 83.6% and -0.714(-1.388, -0.04), I² = 84.4% respectively. There was no significant change in weighted mean difference of glycosylated hemoglobin A1C (HbA1c) % and lipid profiles (mmol/L). Meta-regression did not show any factor significantly affecting the treatment response.

CONCLUSION

Cinnamon reduced FBG and HOMA-IR, level in T2DM and pre-diabetes patients compared to placebo. High heterogeneity observed among included studies warrants further clinical trials after standardization of cinnamon formulation.

Effects of acute intake of grape/pomegranate pomace dietary supplement on glucose metabolism and oxidative stress in adults with abdominal obesity

A controlled acute, cross-over clinical study (NCT02710461) was performed in order to evaluate the effects on glucose metabolism of a grape/pomegranate pomace dietary supplement in subjects with abdominal obesity (aged 40-60, n = 20). A standard 75 g oral glucose tolerance test (OGTT) was administered alone, together with or 10 h after the consumption of 10 g of the dietary supplement, rich in both extractable (0.4 g) and non-extractable (1.4 g) polyphenols. The dietary supplement did not ameliorate glucose or insulin at any sampling time. No improvement in antioxidant capacity was observed in plasma or urine, concordant with no increased urine polyphenol excretion. A tendency towards improved insulin sensitivity was observed when the product was consumed 10 h before glucose solution. These results suggest that a single realistic dose of grape/pomegranate pomace is not able to clearly improve glucose metabolism; chronic intake remains to be evaluated.

Cinnamon and Cassia Nomenclature Confusion: A Challenge to the Applicability of Clinical Data

Several Cinnamomum species' barks are generally labeled as cinnamon, although only Cinnamomum verum carries the common name of true cinnamon. Cassia, a common name for a related species, is rarely used on labels; instead, various cassia types may also be labeled "cinnamon." Confusion of true cinnamon and cassia spices in foods generally does not present a risk to health, except possibly at the highest intake levels. However, clinical studies with Cinnamomum investigational products have been published that inadequately describe or lack botanical identification information. The results of such studies are confounded by an inability to determine which species was responsible for the observed effects. Due to differences in the quality and composition of various Cinnamomum species, safety and efficacy data are not generalizable or transferable. Pharmacopeial monographs for characterizing the identity, composition, purity, quality, and strength of Cinnamomum investigational products should be applied to remove the ambiguity of cinnamon.

Evaluation of pharmacodynamic properties and safety of Cinnamomum zeylanicum (Ceylon cinnamon) in healthy adults: a phase I clinical trial

Background

Cinnamon is considered as a treatment for many ailments in native medicine. Evidence suggests that Cinnamomum zeylanicum (CZ) has anti-microbial, anti-parasitic, anti-oxidant, blood glucose lowering properties and beneficial cardiovascular effects. The present study aims to evaluate Pharmacodynamic properties and safety of CZ in healthy adults using a Phase I Clinical Trial.

Methods

This phase I clinical trial was conducted at the Department of Pharmacology, Faculty of Medicine, University of Colombo, Sri Lanka. Thirty healthy adults were recruited for the study, conducted for a period of 3 months, with the dose of CZ (water extract) increased at monthly intervals (85 mg, 250 mg and 500 mg). Data collection was carried out at baseline and during each monthly follow up visit. Anthropometric, clinical and biochemical assessments were done at baseline and during follow up. Adverse effects and drug compliance was also evaluated.

Results

Twenty eight subjects completed the three months follow up. Mean age was 38.8 ± 10.4 years and 50% were males. There were no significant changes in the anthropometric parameters during the three months follow up. Both systolic and diastolic blood pressure reduced significant during the 1st month and this reduction was sustained throughout follow up. Full blood count, renal function tests, liver function tests, fasting blood glucose, HDL-c, VLDL-d and triglycerides remained within the normal range without any significant alteration during the 3 months. A significant reduction in the TC (p < 0.05) and LDL-c (p < 0.001) was noted at the end of the 3 months follow up period. There were no serious adverse effects (including hypersensitivity) noted. In two participants dyspepsia necessitated the discontinuation of study participation. Drug compliance was between 85 and 95% during the study period.

Conclusions

This is the first phase I clinical trial in health adults evaluating efficacy and safety of CZ. Our results demonstrate no significant side effects and toxicity of CZ, including hepatotoxicity and anti-coagulation properties. CZ demonstrated beneficial anti-hyperlipidaemic and blood pressure lowering effects among healthy adults. Further studies with larger samples and longer durations may be able to elucidate other side effects and better describe the pharmacodynamic properties.

Trial registration

SLCTR/2013/001 (Sri Lanka Clinical Trials Registry: http://www.slctr.lk/trials/106) (Date of Registration: 01/01/2013).

Effects of cinnamon supplementation on antioxidant status and serum lipids in women with polycystic ovary syndrome

Background

The objectives of study were to investigate the effects of cinnamon supplementation on antioxidant status and serum lipids in women with polycystic ovary syndrome (PCOS).

Methods

This double-blind randomized controlled clinical trial was conducted on 84 overweight or obese PCOS patients; aged 20–38 years. Subjects in cinnamon (n = 42) and placebo (n = 42) groups were given 3 cinnamon capsules (each one contained 500 mg cinnamon) or placebo daily for 8 weeks. Fasting blood samples, anthropometric measurements and dietary intake data were gathered at the beginning and at the end of the study. Independent t test, paired t test and analysis of covariance were used to analyze of data.

Results

Cinnamon significantly increased serum total antioxidant capacity (P = 0.005). Malondialdehyde was significantly decreased compared with placebo (P = 0.014). Cinnamon supplementation significantly improved serum level of total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol (all P < 0.05). No significant effect was detected on serum triglyceride level.

Conclusions

Cinnamon supplementation improved antioxidant status and serum lipid profile in women with PCOS and may be applicable for reducing PCOS risk factors.

Cassia cinnamon does not change the insulin sensitivity or the liver enzymes in subjects with impaired glucose tolerance

Background

Published studies have reported conflicting results regarding the effects of cinnamon on glucose, lipids and insulin. To gain further insight into the metabolic effects of Cinnamomum cassia we performed randomized, double-blinded placebo-controlled study using euglycaemic-hyperinsulinaemic clamp.

Methods

Twenty-one subjects with impaired glucose tolerance (IGT) were included in the study (10 or 11 subjects in each group). The study groups were matched for age, gender and body mass index (BMI). Waist-to-hip ratio, BMI, blood pressure, fasting blood glucose, insulin, triglycerides, total cholesterol, low-density lipoprotein, high-density lipoprotein , HbA1c, ASAT, ALAT, bilirubin, ALP, GT and PK were measured before and after the intake of capsules equivalent to 6 g cinnamon twice a day for 12 weeks. The changes in insulin resistance were measured by euglycaemic-hyperinsulinaemic clamp. The Wilcoxon signed rank sum test, the Mann-Whitney U test and Pearson’s chi-squared test were used to analyse the data. Values of p < 0.05 were considered to indicate statistically significant differences.

Results

At enrolment, the groups were similar in terms of age, gender and BMI. Of the 21 randomized patients with IGT, 17 completed the study (8 controls vs. 9 treated). The ingestion of 6 g cinnamon twice a day for 12 weeks had no significant effect on insulin sensitivity, HbA1c, fasting glucose or BMI. No significant changes were seen in lipids or liver enzymes.

Conclusions

This study showed that ingestion of 6 g C. cassia twice a day for 12 weeks did not change the insulin sensitivity or liver enzymes in subjects with IGT.

Acute effect of Ceylon cinnamon extract on postprandial glycemia: alpha-amylase inhibition, starch tolerance test in rats, and randomized crossover clinical trial in healthy volunteers

BACKGROUND

Postprandial hyperglycemia is a known risk factor for the development of several health disorders including type 2 diabetes, obesity, oxidative stress, and cardiovascular diseases. One encouraging approach for a better control of postprandial glycemia is to reduce carbohydrate digestion. Cinnamon extracts have been known for managing blood glucose. However, their effects on inhibiting digestion of carbohydrate have been poorly analyzed to date. The aim of this study was to investigate the acute effect of a specific Ceylon cinnamon hydro-alcoholic extract (CCE) on carbohydrate digestion and post-meal blood glucose reduction.

METHODS

In vitro enzymatic assays and in vivo starch tolerance tests in rats were designed as preclinical assays. Then, a randomized, double-blind, placebo-controlled, cross-over clinical trial was conducted in 18 healthy female and male volunteers. Following the intake of 1 g of CCE, the subjects ate a standardized meal. Blood samples were collected during the 2 hours following the meal to measure glucose and insulin concentrations. Areas under the curves were calculated and statistical differences between the CCE and placebo groups were analyzed using the Mann Whitney-Wilcoxon test.

RESULTS

CCE has demonstrated in the in vitro study that it inhibited pancreatic alpha-amylase activity with an IC50 of 25 μg/mL. In the in vivo study, CCE was shown to acutely reduce the glycemic response to starch in a dose-dependent manner in rats. This effect was significant from the dose of 12.5 mg/kg of body weight. In both, the in vitro and in vivo studies, the hydro-alcoholic extract has shown to be more efficacious than the aqueous extract. In the human clinical trial, 1 g of CCE lowered the area under the curve of glycemia between 0 and 120 min by 14.8% (P = 0.15) and between 0 and 60 min by 21.2% (P < 0.05) compared to the placebo. This effect occurred without stimulating insulin secretion. No adverse effects were reported.

CONCLUSION

These results suggest that Ceylon cinnamon hydro-alcoholic extract (CCE) may provide a natural and safe solution for the reduction of postprandial hyperglycemia and therefore help to reduce the risks of developing metabolic disorders.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02074423 (26/02/2014).

Cinnamon extract improves insulin sensitivity in the brain and lowers liver fat in mouse models of obesity

Objectives

Treatment of diabetic subjects with cinnamon demonstrated an improvement in blood glucose concentrations and insulin sensitivity but the underlying mechanisms remained unclear. This work intends to elucidate the impact of cinnamon effects on the brain by using isolated astrocytes, and an obese and diabetic mouse model.

Methods

Cinnamon components (eugenol, cinnamaldehyde) were added to astrocytes and liver cells to measure insulin signaling and glycogen synthesis. Ob/ob mice were supplemented with extract from cinnamomum zeylanicum for 6 weeks and cortical brain activity, locomotion and energy expenditure were evaluated. Insulin action was determined in brain and liver tissues.

Results

Treatment of primary astrocytes with eugenol promoted glycogen synthesis, whereas the effect of cinnamaldehyde was attenuated. In terms of brain function in vivo, cinnamon extract improved insulin sensitivity and brain activity in ob/ob mice, and the insulin-stimulated locomotor activity was improved. In addition, fasting blood glucose levels and glucose tolerance were greatly improved in ob/ob mice due to cinnamon extracts, while insulin secretion was unaltered. This corresponded with lower triglyceride and increased liver glycogen content and improved insulin action in liver tissues. In vitro, Fao cells exposed to cinnamon exhibited no change in insulin action.

Conclusions

Together, cinnamon extract improved insulin action in the brain as well as brain activity and locomotion. This specific effect may represent an important central feature of cinnamon in improving insulin action in the brain, and mediates metabolic alterations in the periphery to decrease liver fat and improve glucose homeostasis.