Healthy Living Articles

 

Cinnamon and Diabetes

Cinnamon: An effective herbal treatment for diabetes?

July, 2010

cinnamon

The search for effective treatments for diabetes, especially type 2 diabetes, remains a challenge for medical researchers, regardless of their background. As many of you know, many of the oral medications have significant side effects that are not popular with patients, have limited effectiveness, or lack evidence of impacting the course of the disease, including the development of complications. This challenge, combined with an increasing interest in herbal and complementary medicine has led to a search for effective natural therapies that have significant effects on blood sugar levels, blood pressure, etc.

Diabetes Action Research and Education Foundation is the only diabetes organization to specifically prioritize research funding to universities and researchers committed to discovering and evaluating effective natural therapies to help combat diabetes! Your support of Diabetes Action and its research efforts is greatly appreciated, as you and the ones you love will benefit from their contributions to advancing research on natural choices and healthy lifestyles- critical to long-term success in managing diabetes.

Cinnamon, the brown, mildly bitter, mild spicy cooking herb, has gained popularity as an herbal treatment for diabetes because it is readily available and relatively inexpensive. Since this original publication, several others have studied cinnamon in different groups of people and challenged the original findings, while additional publications suggested the type of cinnamon and/or how the extract was made may be significant factors in the effects cinnamon has on blood sugar. Also, many research publications have focused on laboratory measures, which are important in diabetes, but do not fully account for risk; some publications suggest cinnamon may have other benefits, like antioxidant effects and production against "type 3 diabetes" or insulin resistance in the brain. In this article I will review the recent clinical evidence on cinnamon, and provide some guidance on if you should try it yourself!

What Makes Cinnamon "Work"?

Cinnamon contains rather high levels of compounds called "polyphenols"1. Polyphenols refer to the chemical structure of an entire class of compounds that have rather high antioxidant activity, and are typically very effective in reducing the oxidative processes that change fats and lipids into potent inflammatory compounds (e.g. peroxidation). Cinnamon is not the only food/herbal medicine that has high amounts of these polyphenols; other examples include green tea, darkly colored berries, red grapes, some nuts including peanuts, and dark chocolate. Translational research by Roussel et al. supports the antioxidant effects of a water-soluble cinnamon extract (a preparation method that concentrates polyphenols) 2. Some recent studies suggest, for safety and better efficacy, that the water-soluble compounds in cinnamon are the most effective, however good clinical research has not yet compared this extract (and commercially available product) to the whole herb3.

Does Clinical Research Support Cinnamon as an Effective Treatment?

A publication by Dr. Khan and Dr. Anderson reported research supported by Diabetes Action that suggested cinnamon reduced blood sugar for patients with type 2 diabetes.

The first significant clinical study evaluating Cinnamon was published by Khan et al. in 2003.4 In this trial, 60 Pakistani participants took Cinnamon (Cinnamon cassia) orally for 40 days at three different doses (1, 3, or 6 grams per day).After 40 days, significant reductions in fasting blood sugar, cholesterol (including LDL or "bad" cholesterol) and triglycerides were noted at each dose, although the group receiving the 6 grams per day dose did have a larger percent reduction in blood glucose compared to the 1 and 3 gram per day dosing groups (29% vs. ~25%). One limitation in this study is that the results may not be applicable to all people, as the trial was performed in Pakistan, where dietary intake of polyphenol compounds is quite limited, and thus introducing dietary polyphenols in such significant amounts may have different effects than it would in groups of people with more diverse dietary intake of polyphenol compounds, including the United States. The flip side of this criticism is that people in Pakistan are relatively medication naive and take fewer supplements, thus creating a nice "blank slate" for research that avoids potential confounders.

The next trial, published by Mang, et al. in 2006, evaluated a water-soluble extract, corresponding to 3 grams of cinnamon, in 79 German participants with type 2 diabetes for four months.5 Although fasting glucose was lowered at the end of the trial, the reductions were modest compared to the findings by Khan et al.; average reductions were about 10%. Unlike the findings of Khan et al., changes in cholesterol and triglycerides were not significant, nor were changes in hemoglobin A1c.

Additional clinical research on cinnamon was published by Suppapitiporn et al. also in 2006.6 In their clinical trial, 60 Thai participants with type 2 diabetes took 1.5 grams per day of encapsulated whole cinnamon powder or placebo for 3 months. At the end of the trial period, no significant changes were evident in either fasting glucose, hemoglobin A1c or lipids. There was suggestion that a greater percentage of patients in the cinnamon group achieved glucose "control" (i.e. reached a hemoglobin A1c value of < 7%), however this difference (35% vs. 15%) was not statistically significant.

cinnamon sticks

The saga continues with the clinical trial published by Vanschoonbeek et al. in which 25 post-menopausal women with type 2 diabetes, from the Netherlands, were randomized to take either 1.5 grams of ground, whole herb cinnamon or placebo for 6 weeks.

Evaluating the effectiveness of cinnamon at the end of 2006 would have led, I'm afraid, to an assessment of "not effective" based on rather small and highly variable fasting glucose reductions seem across studies. Fear not, we only had to wait a year to get more evidence!

In 2007, Altschuler et al. published the first available clinical trial of cinnamon in participants with type 1 diabetes.8 In this trial, 72 adolescents with type 1 diabetes were randomized to receive either 1 gram/day of cinnamon or placebo for 3 months. At the end of the trial period, no significant changes in hemoglobin A1c, insulin sensitivity, or daily insulin use (units/day). In fact, insulin use actually increased in the cinnamon group. It is important to differentiate this study from the other studies discussed above. Type 1 diabetes is a very different condition than type 2, with different causative factors and pathogenesis. It may be possible that the polyphenols of cinnamon have a sensitizing effect on insulin only in the presence of significant insulin resistance (this may be due to the role lipid peroxides have on inducing insulin resistance, which may be improved with antioxidant polyphenol supplementation).

cinnamon can improve insulin sensitivity in healthy adults, how this evidence applies to people with diabetes is less clear...

In hopes of addressing the limitations in the trial by Khan et al., specifically the population in the study, in 2007 Blevins et al. published the results of their clinical trial performed in the United States.9 In their study, 60 participants with type 2 diabetes and very stable medications were randomly assigned to take cinnamon (1 gram per day) or placebo for 3 months. At the end of 3 months, there were no significant changes in fasting glucose, hemoglobin A1c, insulin, insulin sensitivity or lipid values. Notably a considerable percentage of the participants (~75%) in this trial were taking insulin sensitizing medications, which may have over-powered any modest action of the cinnamon extract.

As you have probably noticed, many researchers attempted to replicate the findings of Khan et al in different populations, but using similar doses, i.e. 1-1.5 grams/day. However, the basis for the dosing in the original trial wasn't specific, rather it was a somewhat arbitrary attempt at performing a dose-response study, and therefore, although reasonable to try these doses again, new research exploring even higher doses stopped until the 2007 publication by Solomon et al.10 In their study, 7 healthy adults without diabetes performed three oral glucose tolerance tests (An oral glucose tolerance test (OGTT) is performed by having a patient drink a standardized solution containing 75 grams of glucose, and then measuring insulin and glucose simultaneously for several hours following. The values are then plotted as a curve; the area under the curve provides meaningful reflections of glucose tolerance and can be used to estimate insulin sensitivity.) preceded by 5 grams of cinnamon, 5 grams of placebo, or 5 grams of cinnamon given 12-hours before the OGTT. Their results demonstrated significant reductions in post-OGTT blood glucose corresponding to measured improvements in insulin sensitivity.

Solomon et al. continued their translational research evaluating the effects of high dose cinnamon powder on insulin sensitivity in healthy adults by evaluating the effects of sustained short-term intake (3 grams per day or placebo for 14 days) on glucose and insulin measures also following OGTT.11 In this study, cinnamon reduced blood glucose following the OGTT, reduced insulin response to the OGTT and improved insulin sensitivity compared with the placebo. However, the effects were lost however almost immediately upon stopping the cinnamon extract.

Although these small, translational trials provide "proof of concept" evidence, i.e. cinnamon can improve insulin sensitivity in healthy adults, how this evidence applies to people with diabetes is less clear. First of all, the dose used here, 3 and 5 grams per day, are very large. One concern I have is the differences in liver health in "healthy" adults vs. adults with diabetes. As many patients with diabetes also suffer from elevated liver enzymes due to a condition of increased fat deposition in the liver (a condition called non-alcohol steatohepatitis (NASH) or "fatty liver" disease), the effects of such large doses of cinnamon on liver health should be studied more before doses of cinnamon this large are considered for routine use.

...a greater reducation in A1c was evident in the cinnamon group...this finding was highly statistically significant.

Although the clinical trials that have been published on cinnamon generally show very few, if any, side effects, none of these trials have reported very systematic approaches to measuring side effects and none of the studies provide evidence of safety based on laboratory results.

Just when findings were starting to look really quite bleak for a role of cinnamon in lowering blood sugar in people with diabetes, Dr. Crawford published a clinical trial (apparently performed all by himself) evaluating the impact of whole-herb cinnamon (Cinnamon cassia, 1 gram per day for 3 months) vs. placebo in 109 patients with type 2 diabetes recruited from three primary care clinics on a US military base. Cinnamon was added to normal medications and medication changes were not meaningfully different between groups at the end of the study. In this clinical trial, a ~0.5% greater reduction in hemoglobin A1c was evident in the cinnamon group compared to the placebo group; this finding was highly statistically significant. This trial is notable for several reasons, including its size (the largest randomized trial performed thus far) and its "Western" participant group from a typical clinical practice setting.

For ease of reviewing the findings of all of these trials, a summary table of the results is included here as Table 1.

Table 1: Comparison of Recent Clinical Trials of Cinnamon in Diabetes

 

 

 

 

 

Main Effects

Author
& Date

Patient population

Type of cinnamon

Dose & Duration

Glucose/ HbA1c

Insulin sensitivity

Lipids

Other Effects

Khan et al. 20034

Pakistani; Type 2 diabetes; n=60

Cinnamon cassia; whole herb

1,3 or 6 grams/day for 40 days

Significant reduction in fasting glucose (~25-29%)

Not reported

Significant reductions in total and LDL cholesterol and triglyceride

Not reported

Mang
et al. 20065

German, Type 2 diabetes; n=79

Cinnamon cassia; water-soluble extract

Equivalent to 3 grams/day for 4 months

Significant reduction in fasting glucose (~10%); no change in HbA1c

Not reported

No significant changes

Not reported

Suppapiti-porn
et al. 20066

Thai, Type 2 diabetes; n=60

Cinnamon cassia; whole herb

1.5 grams/day for 3 months

No significant changes; 20% more patients achieved HbA1c < 7.0%

No significant changes

No significant changes

Not reported

Vanschoon
-beeket al. 20067

European, menopausal women with Type 2 diabetes, n=25

Cinnamon cassia; whole herb

1.5 grams/day for 1.5 months

No significant changes

Not reported

No significant changes

Not reported

Altschuler
et al.  20078

US adolescents with Type 1 diabetes, n=72

Cinnamon cassia; whole herb

1 gram/day for 3 months

No significant changes

No significant changes

Not reported

Not reported

Blevins
et al. 20079

US adults with Type 2 diabetes, n=60

Cinnamon cassia; whole herb

1 gram/day for 3 months

No significant changes

No significant changes

No significant changes

Not reported

Crawford
200912

US adults with Type 2 diabetes, n=109

Cinnamon cassia; whole herb 

1 gram/day for 3 months

Significant 0.5% reduction in HbA1c

Not reported

Not reported

Not reported

Roussel
et al.; 20092

Overweight French adults with pre-diabetes, n=22

Cinnamon cassia; water-soluble extract 

1 gram/day for 12 weeks

No significant changes, but fasting glucose reduced 11%

Not reported

Not reported

Improved antioxidant status, including reduced protein and lipid oxidation

Stoeker
et al.; 201013

Chinese adults with pre-diabetes; n=137

Cinnamon cassia; water-soluble extract 

500 mg/day for 8 weeks

No significant changes; fasting glucose reduced 7.5%; 12% reduction in glucose after a tolerance test

Not reported

No significant changes

Not reported

Conclusions & Research Gaps

At the present time, the clinical research on cinnamon as an effective treatment for diabetes is lacking. The evidence of either glucose- or lipid-lowering properties of cinnamon is mixed, and the evidence for insulin sensitizing effects of cinnamon is significantly limited.

...the findings suggest the possibility of a small to modest effect of supplemental cinnamon...

Although the "proof-of-concept" data provided in two separate studies by Solomon et al. suggests insulin sensitization by cinnamon is possible, the extension of these findings to patients with type 2 diabetes is not supported by substantive clinical trial evidence. This limitation may depend on the medications used by the patients in the clinical trials, as modest insulin sensitizing effects of cinnamon may be masked or negated by more powerful effects of insulin sensitizing medications. However, despite the inconsistent results, the most recent, largest and most applicable clinical trial performed to date in the United States, does suggest modest benefit (~0.5% reduction in HbA1c) of cinnamon when added to routine clinical care.12 Also, to date there is no published evidence that cinnamon has glucose lowering effects in patients with type 1 diabetes, possible because differences in the pathogenesis of type 1 compared to type 2.

In my assessment, the findings of the clinical trials summarized above suggest the possibility of a small to modest effect of supplemental cinnamon, most likely due to small changes in insulin sensitivity. These effects may be due to reductions in oxidative stress, especially reductions in the oxidation of lipids.

For those patients seeking small reductions in glucose...a trial of cinnamon supplementation appears to be safe and may result in small improvements.

No clinical trial that is generalizable to people in the United States has demonstrated more than a modest impact on risk factors, and several trials have shown no effects on any parameters measured. These findings are consistent in that the results are mild to non-existent in all studies, i.e. large effects have not been demonstrated by any investigation team.

Several large research gaps exist regarding cinnamon. The clinical trials performed so far are very short in duration, with the longest being only 4 months. These trials are barely long enough to demonstrate changes in hemoglobin A1c and may be too short to demonstrate clinical change from mild insulin sensitization. Evidence supporting the effectiveness of cinnamon may become more apparent from longer-term use, but this question has not been evaluated carefully. Additionally, the question of whole-herb vs. water-soluble extract deserves inquiry. Ideally, the whole-herb extract would be directly compared to the water-soluble extract in a head-to-head clinical trial implemented in an independent, academic clinic in a multi-ethnic population.

The Bottom Line

Patients with poorly controlled diabetes (HbA1c > 6.5-7%) should not rely on cinnamon alone in order to achieve better glucose control. However, for those patients seeking small reductions in glucose in order to tighten control (especially if not taking insulin sensitizing medications like metformin, rosiglitazone or pioglitazone), a trial of cinnamon supplementation appears to be safe and may result in small improvements. At this point in time, there is minimal evidence that supports a benefit of water-soluble extracts compared to whole-herb cinnamon. Regular use of cinnamon in cooking as a culinary spice is likely to be perfectly safe and may offer small benefits especially when used with a healthy diet rich in vegetables, lean proteins and whole grains.



Dr. Ryan Bradley, ND, Doctor of Naturopathy

 

Ryan Bradley, ND, MPH is a naturopathic doctor, clinical researcher and epidemiologist in San Diego, CA. He is Assistant Director of Research at the National College of Natural Medicine in Portland, OR. In addition to his research, he is a practicing clinician specializing in natural and integrative approaches to treating type 2 diabetes, chronic kidney disease and heart disease at Pacific Pearl La Jolla.

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References

1. Anderson RA, Broadhurst CL, Polansky MM, et al. Isolation and characterization of polyphenol type-A polymers from cinnamon with insulin-like biological activity. J Agric Food Chem 2004;52:65-70.
2. Roussel AM, Hininger I, Benaraba R, Ziegenfuss TN, Anderson RA. Antioxidant effects of a cinnamon extract in people with impaired fasting glucose that are overweight or obese. J Am Coll Nutr 2009;28:16-21.
3. Broadhurst CL, Polansky MM, Anderson RA. Insulin-like biological activity of culinary and medicinal plant aqueous extracts in vitro. J Agric Food Chem 2000;48:849-52.
4. Khan A, Safdar M, Ali Khan MM, Khattak KN, Anderson RA. Cinnamon improves glucose and lipids of people with type 2 diabetes. Diabetes Care 2003;26:3215-8.
5. Mang B, Wolters M, Schmitt B, et al. Effects of a cinnamon extract on plasma glucose, HbA, and serum lipids in diabetes mellitus type 2. Eur J Clin Invest 2006;36:340-4.
6. Suppapitiporn S, Kanpaksi N. The effect of cinnamon cassia powder in type 2 diabetes mellitus. J Med Assoc Thai 2006;89 Suppl 3:S200-5.
7. Vanschoonbeek K, Thomassen BJ, Senden JM, Wodzig WK, van Loon LJ. Cinnamon supplementation does not improve glycemic control in postmenopausal type 2 diabetes patients. J Nutr 2006;136:977-80.
8. Altschuler JA, Casella SJ, MacKenzie TA, Curtis KM. The effect of cinnamon on A1C among adolescents with type 1 diabetes. Diabetes Care 2007;30:813-6.
9. Blevins SM, Leyva MJ, Brown J, Wright J, Scofield RH, Aston CE. Effect of cinnamon on glucose and lipid levels in non insulin-dependent type 2 diabetes. Diabetes Care 2007;30:2236-7.
10. Solomon TP, Blannin AK. Effects of short-term cinnamon ingestion on in vivo glucose tolerance. Diabetes Obes Metab 2007;9:895-901.
11. Solomon TP, Blannin AK. Changes in glucose tolerance and insulin sensitivity following 2 weeks of daily cinnamon ingestion in healthy humans. Eur J Appl Physiol 2009;105:969-76.
12. Crawford P. Effectiveness of cinnamon for lowering hemoglobin A1C in patients with type 2 diabetes: a randomized, controlled trial. J Am Board Fam Med 2009;22:507-12.
13. Stoecker BJ ZZ, Luo R, Mu X, Guo X, Liu Y, Guo Q, Zhou J, Kong J, Zhou Z, Cui Z, Anderson RA. . Cinnamon extract lowers blood glucose in hyperglycemic subjects. FASEB J 2010; 24.

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