In December of 2003, a randomized study was published in Diabetes Care regarding the beneficial effects of cinnamon on glycemic regulation in patients with type 2 diabetes mellitus (Khan et al.). Since that time, cinnamon supplements have received a lot of attention.

History of cinnamon

Cinnamon has long been recognized as having certain medicinal properties. Historically, cinnamon has been used to treat gastrointestinal symptoms and diabetes mellitus among other things[1]. As early as 2000 BC, cinnamon was being imported from China by the Egyptians as both a medication and a spice. It was also used in Roman times: Emperor Nero burned a year’s supply of cinnamon during his wife’s funeral to win the favor of the gods[2]. During the middle ages, owning spices was a status symbol, and cinnamon was used as a cough medicine and for the treatment of gastrointestinal complaints. It was also used to mask the odor of rotting meat[3]. During colonial times, Ceylon (now Sri Lanka), with its native cinnamon trees, was originally in the hands of the Portuguese. In the middle of the 17th century, this area was claimed by the Dutch East India Company, after which they had a virtual world wide monopoly on the cinnamon trade[4]. Current processing techniques are still based on techniques developed during that time[5].

Rationale for cinnamon’s effectiveness in the treatment of diabetes

It is not entirely clear where cinnamon affects the glucose metabolism pathway. Several of the components of cinnamon may play a role. Methylhydroxychalcone polymer stimulates the autophosphorylation of insulin receptors, thereby causing increased glucose uptake by the cell. At the same time, it causes an increase in the activity of the enzyme glycogen synthetase[6]. As a result, these mechanisms lower blood glucose levels. Furthermore, methylhydroxychalconpolymer may work synergistically with insulin. Activation of the insulin receptor kinase enzyme may also explain cinnamon’s possible effect of lowering blood glucose levels[7]. Several in vitro studies have demonstrated an insulin mimetic effect for cinnamon or cinnamon extract[8][9][10][11]. Another study, however, showed an antagonistic interaction between cinnamon and insulin[12].

Adverse effects

Theoretically, cinnamon could cause a number of adverse effects. Coumarin and essential oils are two of the components which make up cinnamon. Natural coumarin may have an effect on blood clotting[13][14]. The essential oils in cinnamon may cause allergic reactions[15][16]. Cinnamon extract generally contains less of these two components than pure cinnamon. One patient in one of the studies developed urticaria after taking cinnamon[17]. Upon further investigation it was discovered that more members of this patient’s family were allergic to cinnamon. Certain components of cinnamon have been shown to have both teratogenic and carcinogenic effects in animal studies and in case reports[18][19][20]. The German federal Institute for Risk Assessment (BfR) stated in a 2006 report that health risks as the result of ingesting high daily doses of cinnamon could not be ruled out[^21].

Clinical evidence

Many animal studies have shown that cinnamon improves glycemic control. However, in 5 studies published before 2007 and performed in humans, three of which were in T2DM patients, only one placebo-controlled trial found that cinnamon intake was associated with positive effects on fasting plasma glucose. But none of the studies reported an improvement in HbA1c[21][22][^24][^25][^26]. The only study with beneficial effects was a study performed in Pakistan[^27]. Unfortunately, the researchers did not measure HbA1c. Despite striking baseline differences in fasting glucose between groups (varying from 11.4 to 16.7 mmol/L on average), neither correction for baseline differences nor the results of placebo-controlled analyses were presented.

Five studies published more recently do not give more hope. One study was performed in 8 healthy men in the UK. This was a singleblind, placebo-controlled, randomized cross-over study in which subjects ingested 3 grams of cinnamon per day for a period of 14 days. After 14 days, no significant differences in postprandial glucose concentrations were found[^28]. Another study was performed in the USA in non-diabetic subjects with fasting glucose levels between 5.6 and 6.9 mmol/L[^29]. Twenty-two subjects were randomized in a double-blind, placebocontrolled trial, in which they were given either 500 mg of cinnamon extract per day or placebo for a period of 12 weeks. In the cinnamon group, fasting glucose decreased significantly from 6.5 mmol/L to 5.9 mmol/L, whereas in the placebo group fasting glucose increased from 6.2 mmol/L to 6.3 mmol/L. Unfortunately, the baseline difference of 0.3 mmol/L was not taken into account in the statistical analyses. Also, two trials were found that were performed in patients with T2DM[^30][^31]. The first of these two trials was a single-blind, randomized, placebo-controlled trial in 60 patients in Thailand[^32]. After 12 weeks the cinnamon group showed a 0.2% higher decrease in HbA1c compared to the placebo group, but this was not statistically significant. The second study was performed in 60 patients in the USA and had a randomized, doubleblind, placebo-controlled design[^33]. Patients in the intervention group received 1 gram of cinnamon each day for a period three months. HbA1c in the cinnamon group increased 0.2% (7.2% to 7.4%), compared to 0.1% (7.1% to 7.2%) in de placebo group (no significant difference). In two systematic reviews, which did not include the Thai study, the meta-analysis indicated that there were non-significant effects on fasting glucose in patients with T2DM of -1.0 mmol/L (95% CI: -2.6, 0.7) and on HbA1c of 0.01% (95% CI: -0.20, 0.22)[^34]. Another systematic review concluded that the effect of cinnamon they found on fasting glucose of -0.49 mmol/L was significant[^35]. Unfortunately, effects on HbA1c were not included in this review.

A recent randomized, placebo-controlled, double-blind clinical trial give some new hope. Mean HbA1c was significantly decreased in the cinnamon group (8.22% to 7.86%) compared with placebo group (8.55% to 8.68%)[^36]. Unfortunately, this trial has some important unresolved methodological issues, that has not been answered by the authors[^37].


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  3. ^ Klein RM. The Green world. An introduction to plants and people. New YHarper and Row; 1979.

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  10. ^ Kim SH, Hyun SH, Choung SY. Antioxidative effects of Cinnamomi cassiae and Rhodiola rosea extracts in liver of diabetic mice. Biofactors. 2006;209-19.

  11. ^ Cao H, Polansky MM, Anderson RA. Cinnamon extract and polyphenols affect the expression of tristetraprolin, insulin receptor, and glucose transporter 4 in mouse 3T3-L1 adipocytes. Arch Biochem Biophys. 2007;214-22.

  12. ^ Roffey B, Atwal A, Kubow S. Cinnamon water extracts increase glucose uptake but inhibit adiponectin secretion in 3T3-L1 adipose cells. Mol Nutr Food Res. 2006;739-45.

  13. ^ Hoult JR, Payá M. Pharmacological and biochemical actions of simple natural products with therapeutic potential. Gen Pharmacol. 1996;713-22.

  14. ^ Kidane AG, Salacinski H, Tiwari A, Bruckdorfer KR, Seifalian AM. Anticoagulant and antiplatelet their clinical and device application(s) together with usages to engineer surfaces. Biomacromolecules. 2004;798-813.

  15. ^ WHO. Corex Cinnamoni. WHO Monographs on selected medicinal plants. GWorld Health Organisation; 1999. p.95-104.

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  17. ^ Altschuler JA, Casella SJ, Mackenzie TA, Curtis KM. The effect of cinnamon on A1C among adolescents with type 1 diabetes. Diabetes Care. 2007;813-6.

  18. ^ A, Monteiro A, Martins C, Kranendonk M, Laires A, Rueff J, et al. Genotoxicity and endoreduplication inducing activity of the food flavouring eugenol. Mutagenesis. 2006;199-204.

  19. ^ Westra WH, McMurray JS, Califano J, Flint PW, Corio RL. Squamous cell carcinoma of the tongue associated with cinnamon gum a case report. Head Neck. 1998;430-3.

  20. ^ Mantovani A, Stazi AV, Macri C, Ricciardi C, Piccioni A, Badellino E. Pre-natal (segment II) toxicity study of cinnamic aldehyde in the Sprague-Dawley rat. Food Chem Toxicol. 1989;781-6.

  21. ^ Altschuler JA, Casella SJ, Mackenzie TA, Curtis KM. The effect of cinnamon on A1C among adolescents with type 1 diabetes. Diabetes Care. 2007;813-6.

  22. ^ Kleefstra N, Logtenberg SJ, Houweling ST, Verhoeven S, Bilo HJ. Cnot suitable for the treatment of diabetes mellitus. Ned Tijdschr Geneeskd. 2007 Dec 22;151(51):2833-7.


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