Cinnamomum zeylanicum, Cinnamon cassia
Principal Proposed Uses
• High Cholesterol; Diabetes
Other Proposed Uses
• Antimicrobial; Improving Appetite; Indigestion; Polycystic Ovary Disease; Ulcers
Most Americans consider cinnamon a simple flavoring, but in traditional Chinese medicine, it's one of the oldest remedies, prescribed for everything from diarrhea and chills to influenza and parasitic worms. Cinnamon comes from the bark of a small Southeast Asian evergreen tree and is available as an oil, extract, or dried powder. It's closely related to cassia ( C. cassia ) and contains many of the same components, but the bark and oils from C. zeyleanicum are thought to have a better flavor.
What Is Cinnamon Used for Today?
Based on the results of one preliminary double-blind, placebo-controlled study, cinnamon has been widely advertised as an effective treatment for type 2 diabetes as well as high cholesterol . However, the evidence for this is mixed.
Preliminary results from test tube and animal studies suggest that cinnamon oil and cinnamon extract have antifungal, antibacterial, and antiparasitic properties. 4-10 For example, cinnamon has been found to be active against Candida albicans , the fungus responsible for vaginal yeast infections and thrush (oral yeast infection), Helicobacter pylori (the bacteria that causes stomach ulcers), and even head lice. However, it's a long way from studies of this type to actual proof of effectiveness. Until cinnamon is tested in double-blind human trials, we can't conclude that it can successfully treat these or any other infections. (For why double-blind studies are so important, see Why Does This Database Rely on Double-blind Studies? )
What is the Scientific Evidence for Cinnamon?
Based on previous animal studies that had suggested potential benefits of cinnamon for diabetes , 11,12 researchers in Pakistan performed a double-blind, placebo-controlled trial. 19 In this 40-day study, 60 people with type 2 diabetes were given cinnamon at a dose of 1, 3, or 6 g daily. The results reportedly indicated that use of cinnamon improved blood sugar levels by 18%-29%, total cholesterol by 12%-26%, LDL (“bad”) cholesterol by 7%-27%, and triglycerides by 23%-30%. These results were said to be statistically significant as compared to the beginning of the study and to the placebo group.
However, this study has some odd features. The most important is that it found no significant difference in benefit between the various doses of cinnamon. This is called lack of a dose-related effect, and it generally casts doubt on the results of a study. The researchers counter that perhaps even 1 g of cinnamon is sufficient to produce the maximum cholesterol-lowering effect, and therefore, higher doses simply didn’t add any further benefit. There is another problem with this study as well: no improvements were seen in the placebo group. This too is unusual, and also casts doubt on the results.
In an attempt to replicate these results, a group of Dutch researchers performed a carefully designed 6-week double-blind, placebo-controlled study of 25 people with diabetes. 20 All participants were given 1.5 g of cinnamon daily. The results failed to show any detectable effect on blood sugar, insulin sensitivity, or cholesterol profile. Although this second study was smaller than the first because it had fewer groups, overall, its statistical validity is similar. These unsupportive results were confirmed in a Thai study enrolling 60 people: 1.5 g of cinnamon daily failed to produce any benefit. 24 On the other hand, a double-blind study of 79 people that used 3 g instead of 1.5 g daily did find that cinnamon improved blood sugar levels. 21 And, a randomized trial involving 58 people with type 2 diabetes also concluded that 2 g of cinnamon daily reduced HbA1c levels (a measurement of blood sugar levels over time), as well as high blood pressure. 27
In yet another small study involving 22 prediabetic patients with metabolic syndrome, researchers found that an extract containing 500 mg cinnamon given once daily was effective at modestly reducing fasting blood sugar and systolic blood pressure, and increasing lean body weight. However, the low dosage of cinnamon used in this study raises concerns about the reliability of these results. 26 And, a very small study that evaluated cinnamon for improving blood sugar control in women with polycystic ovary disease found evidence of benefit. 22
The bottom line: At present, it would be premature to consider cinnamon an evidence-based treatment for type 2 diabetes or high cholesterol, but it has definitely shown some promise.
Regarding type 1 diabetes, a study of 72 adolescents failed to find benefit with cinnamon taken at a dose of 1 g daily. 23
A meta-analysis (formal statistical review) of all published evidence concluded that, thus far, cinnamon has not yet been shown to have any effect on blood sugar levels in people with diabetes. 25
The bottom line: The evidence regarding cinnamon as a treatment for diabetes is highly inconsistent, suggesting that if cinnamon is indeed effective, its benefits are minimal at most.
Typical recommended dosages of ground cinnamon bark are 1 to 4 g daily. Cinnamon oil is generally used at a dose of 0.05 to 0.2 g daily. 13
As a widely used food spice, ground cinnamon bark is believed to be safe. However, little is known about the maximum safe dosage of cinnamon found in capsules and in essential oil . Confusing the picture is the fact that Ceylon cinnamon (sometimes referred to as "true cinnamon") is different than the cassia variety. Only the latter contains significant amounts of coumarin, which has been shown to cause liver and kidney damage at high doses in rats and other animals. 28 Although there is limited evidence of such harm occurring in humans, it would be prudent for people with known liver or kidney disease to avoid dietary supplements containing cassia cinnamon. There is some evidence that high doses of cinnamon oil might depress the central nervous system. 14 Germany's Commission E recommends that pregnant women should avoid taking cinnamon oil or high doses of the bark. 15
When used topically, cinnamon bark oil may cause flushing and a burning sensation. 16 Some people have reported strong burning sensations or mouth ulcers after chewing cinnamon-flavored gum or candy. 17,18 However, these reactions disappeared within days of discontinuing the gum.
1. Blumenthal M, ed. The Complete Commission E Monographs, Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative Medicine Communications; 1998: 110.
2. Akira T, Tanaka S, Tabata M. Pharmacological studies on the antiulcerogenic activity of Chinese cinnamon. Planta Med. 1986;52:440-443.
3. Tanaka S, Yoon YH, Fukui H, et al. Antiulcerogenic compounds isolated from Chinese cinnamon. Planta Med. 1989;55:245-248.
4. Singh HB, Srivastava M, Singh AB, et al. Cinnamon bark oil, a potent fungitoxicant against fungi causing respiratory tract mycoses. Allergy. 1995;50:995-999.
5. Quale JM, Landman D, Zaman MM, et al. In vitro activity of Cinnamomum zeylanicum against azole resistant and sensitive Candida species and a pilot study of cinnamon for oral candidiasis. Am J Chin Med. 1996;24:103-109.
6. Tabak M, Armon R, Potasman I, et al. In vitro inhibition of Heliobacter pylori by extracts of thyme. J Appl Bacteriol. 1996;80:667-672.
7. Azumi S, Tanimura A, Tanamoto K. A novel inhibitor of bacterial endotoxin derived from cinnamon bark. Biochem Biophys Res Commun. 1997;234:506-510.
8. Oishi K, Mori K, Nishiura Y. Food hygienic studies on Anisakinae larvae. Effects of some spice essential oils and food preservatives on mortality of Anisakinae larvae. Bull Jap Soc Sci Fish. 1974;40:1241-1250.
9. Veal L. The potential effectiveness of essential oils as a treatment for head lice, Pediculus humanus capitis . Complement Ther Nurs Midwifery . 1996;2:97-101.
10. Quale JM, Landman D, Zaman MM, et al. In vitro activity of Cinnamomumzeylanicum against azole resistant and sensitive Candida species and a pilot study of cinnamon for oral candidiasis. Am J Chin Med . 1996;24:103-109.
11. Imparl-Radosevich J, Deas S, Polansky MM, et al. Regulation of PTP-1 and insulin receptor kinase by fractions from cinnamon: implications for cinnamon regulation of insulin signalling. Horm Res . 1998;50:177-182.
12. Onderoglu S, Sozer S, Erbil KM, et al. The evaluation of long-term effects of cinnamon bark and olive leaf on toxicity induced by streptozotocin administration to rats. J Pharm Pharmacol . 1999;51:1305-1312.
13. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs, and Cosmetics. 2nd ed. New York, NY: Wiley; 1996: 168.
14. Harada M, Ozaki Y. Pharmacological studies on Chinese cinnamon. Central effects of cinnamaldehyde [in Japanese]. Yakugaku Zasshi . 1972;92:135-140.
15. Blumenthal M, ed. The Complete Commission E Monographs, Therapeutic Guide to Herbal Medicines . Boston, MA: Integrative Medicine Communications; 1998: 110.
16. Perry PA, Dean BS, Krenzelok EP. Cinnamon oil abuse by adolescents. Vet Hum Toxicol . 1990;32:162-164.
17. Allen CM, Blozis GG. Oral mucosal reactions to cinnamon-flavored chewing gum. J Am Dent Assoc. 1988;116:664-667.
18. Mihail RC. Oral leukoplakia caused by cinnamon food allergy. J Otolaryngol . 1992;21:366-367.
19. Khan A, Safdar M, Ali Khan MM, et al. Cinnamon improves glucose and lipids of people with Type 2 diabetes. Diabetes Care . 2003;26:3215-3218.
20. Vanschoonbeek K, Thomassen BJ, Senden JM, et al. Cinnamon supplementation does not improve glycemic control in postmenopausal type 2 diabetes patients. J Nutr . 2006;136:977-980.
21. 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;36:340-344.
22. Wang JG, Anderson RA, Chu MC, et al. The effect of cinnamon extract on insulin resistance parameters in polycystic ovary syndrome: a pilot study. Fertil Steril . 2007 Feb 9. [Epub ahead of print]
23. Altschuler JA, Casella SJ, Mackenzie TA, et al. The effect of cinnamon on A1C among adolescents with type 1 diabetes. Diabetes Care. 2007;30:813-816.
24. Suppapitiporn S, Kanpaksi N, Suppapitiporn S. The effect of cinnamon cassia powder in type 2 diabetes mellitus. J Med Assoc Thai. 2006;89(suppl 3):S200-S205.
25. Baker WL, Gutierrez-Williams G, White CM, et al. The effect of cinnamon on glucose control and lipid parameters. Diabetes Care. 2007 Oct 1. [Epub ahead of print]
26. Ziegenfuss TN, Hofheins JE, Mendel RW, et al. Effects of a water-soluble cinnamon extract on body composition and features of the metabolic syndrome in pre-diabetic men and women. J Int Soc Sports Nutr. 2006;3:45-53.
27. Akilen R, Tsiami A, Devendra D, Robinson N. Glycated haemoglobin and blood pressure-lowering effect of cinnamon in multi-ethnic Type 2 diabetic patients in the UK: a randomized, placebo-controlled, double-blind clinical trial. Diabet Med. 2010;27(10):1159-1167.
28. Lungarini S, Aureli F, Coni E. Coumarin and cinnamaldehyde in cinnamon marketed in Italy: a natural chemical hazard? Part A, Chemistry, Analysis, Control, Exposure & Risk Assessment. Food Additives & Contaminants. 2008;25(11):1297-1305.
Last reviewed August 2013 by EBSCO CAM Review Board
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