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Cinnamon (Cinnamomum zeylanicum)

Cinnamon is one of the most extensively studied spices in terms of potential health benefits. This review examines the scientific evidence for cinnamon's therapeutic properties, appropriate dosing, safety considerations, and commercial applications.

Image source and license: https://commons.wikimedia.org/wiki/File:Cinnamomum_zeylanicum_%28Cinnamon%29_tree_in_RDA,_Bogra_01.jpg.
Modified by Peter Jorgensen.

Botanical Information and Types

The term "cinnamon" commonly refers to two main species, which are often confused but have different chemical compositions and potentially different health effects:

• Ceylon cinnamon (Cinnamomum verum, formerly C. zeylanicum) – Also known as "true cinnamon" or "Sri Lankan cinnamon"
• Cassia cinnamon (Cinnamomum cassia or C. aromaticum) – Also known as "Chinese cinnamon"
• Other less common varieties include Cinnamomum burmanni (Indonesian cinnamon), Cinnamomum loureiroi (Vietnamese cinnamon or Saigon cinnamon)

A critical distinction is that Cassia cinnamon contains significantly higher levels of coumarin, a naturally occurring compound that may cause liver damage when consumed in large amounts, compared to Ceylon cinnamon.

Bioactive Compounds

Cinnamon's therapeutic effects are primarily attributed to these bioactive compounds:

• Cinnamaldehyde – The primary active component giving cinnamon its flavor and aroma
• Proanthocyanidins – Polyphenolic compounds with antioxidant properties
• Eugenol – A phenolic compound with antimicrobial properties
• Cinnamic acid – A phenolic acid with antioxidant effects
• Essential oils (primarily in Ceylon cinnamon)
• Coumarin – Found in higher concentrations in Cassia cinnamon

Evidence-Based Health Benefits

Based on recent systematic reviews and meta-analyses, cinnamon has demonstrated the following effects with varying levels of evidence:

Strong Evidence

• Glycemic control: Multiple meta-analyses confirm cinnamon's ability to moderately reduce fasting blood glucose levels and improve insulin sensitivity in type 2 diabetes patients.
• Antioxidant activity: Cinnamon extracts exhibit potent free radical scavenging abilities in both in vitro and in vivo studies.
• Lipid profile improvement: Modest but statistically significant reductions in total cholesterol, LDL cholesterol, and triglycerides.

Moderate Evidence

• Antimicrobial effects: Demonstrated efficacy against various bacteria, fungi, and viruses in laboratory studies, though clinical applications remain limited.
• Anti-inflammatory properties: Reduction in inflammatory markers in several human trials and animal models of inflammation.
• Neurodegenerative disease protection: Emerging evidence for potential benefits in Alzheimer's and Parkinson's disease models through multiple neuroprotective mechanisms.

Preliminary Evidence

• Gastrointestinal health: Potential benefits for irritable bowel syndrome and functional dyspepsia.
• Blood pressure reduction: Some studies show modest hypotensive effects, but results are inconsistent.
• Cancer prevention: Laboratory and animal studies suggest anti-cancer properties, but human evidence remains limited.
• Weight management: May contribute to weight loss when combined with dietary modification, but effects are modest.
• Polycystic ovary syndrome (PCOS): Preliminary studies suggest improvements in menstrual cyclicity and insulin resistance.

Recommended Dosages

Clinical studies have utilized varying dosages, making standardized recommendations challenging. However, based on the available evidence:

• For glycemic control in diabetes: 1-6 g of cinnamon powder daily, typically divided into 2-3 doses
• For lipid profile improvement: 1-3 g daily
• For standardized extracts: 120-250 mg of water-soluble extracts standardized to contain 3-4% type-A polymers
• Duration: Most studies showing benefits have lasted between 4-16 weeks

Important note: Standardization of cinnamon preparations varies widely across studies, making direct comparisons difficult. When possible, preparations standardized to cinnamaldehyde content (typically 1-2%) or type-A polyphenols are preferred for therapeutic purposes.

Maximum Efficacious Range and Higher Doses

Few studies have systematically investigated dose-response relationships for cinnamon. The available evidence suggests:

• Doses above 6 g daily have not consistently demonstrated additional benefits over lower doses
• Limited research exists on very high doses (>10 g daily) due to safety concerns, particularly with Cassia cinnamon
• A significant knowledge gap exists regarding the optimal therapeutic window for different health conditions

Studies examining high-dose cinnamon extracts have primarily focused on acute toxicity rather than enhanced efficacy. This represents a notable gap in the research literature.

Side Effects and Safety Considerations

Cinnamon is generally recognized as safe (GRAS) by the FDA when used in typical culinary amounts. However, therapeutic doses may present certain risks:

• Coumarin toxicity: Primarily a concern with Cassia cinnamon, which contains 2-5% coumarin compared to 0.004% in Ceylon cinnamon. Excessive coumarin intake may cause liver damage, especially with prolonged use
• Allergic reactions: Contact dermatitis and oral allergic syndrome have been reported, particularly in occupational settings
• Blood-thinning effects: May enhance the effects of anticoagulant medications
• Hypoglycemia: Potential concern when used alongside diabetes medications
• Gastrointestinal distress: Higher doses may cause digestive upset in sensitive individuals
• Pregnancy concerns: Medicinal doses are not recommended during pregnancy due to potential uterine stimulation

The European Food Safety Authority has established a Tolerable Daily Intake (TDI) for coumarin at 0.1 mg/kg body weight. For a 70 kg adult, this equates to approximately 7 mg of coumarin, which could be exceeded by consuming just 1-2 g of Cassia cinnamon daily.

Conclusion

Cinnamon shows promising therapeutic potential for several health conditions, particularly for glycemic control, lipid profile improvement, and as an antioxidant. However, the quality of evidence varies considerably across health claims. The distinction between Ceylon and Cassia cinnamon is critical when considering therapeutic applications due to safety concerns with coumarin content in Cassia varieties. More research is needed to establish optimal dosing regimens, standardization methods, and to investigate potential drug interactions.

References

Allen, R. W., Schwartzman, E., Baker, W. L., Coleman, C. I., & Phung, O. J. (2013). Cinnamon use in type 2 diabetes: an updated systematic review and meta-analysis. The Annals of Family Medicine, 11(5), 452-459.

Costello, R. B., Dwyer, J. T., Saldanha, L., Bailey, R. L., Merkel, J., & Wambogo, E. (2016). Do cinnamon supplements have a role in glycemic control in type 2 diabetes? A narrative review. Journal of the Academy of Nutrition and Dietetics, 116(11), 1794-1802.

Hajimonfarednejad, M., Nimrouzi, M., Heydari, M., Zarshenas, M. M., Raee, M. J., & Jahromi, B. N. (2018). Insulin resistance improvement by cinnamon powder in polycystic ovary syndrome: A randomized double‐blind placebo controlled clinical trial. Phytotherapy Research, 32(2), 276-283.

Kawatra, P., & Rajagopalan, R. (2015). Cinnamon: Mystic powers of a minute ingredient. Pharmacognosy research, 7(Suppl 1), S1.

Khan, A., Safdar, M., Ali Khan, M. M., Khattak, K. N., & Anderson, R. A. (2003). Cinnamon improves glucose and lipids of people with type 2 diabetes. Diabetes care, 26(12), 3215-3218.

Kim, J. I., Lee, J. H., Song, Y., Kim, Y. T., Lee, Y. H., & Kang, H. (2018). Oral consumption of cinnamon enhances the expression of immunity and lipid absorption genes in the small intestinal epithelium and alters the gut microbiota in normal mice. Journal of Functional Foods, 49, 96-104.

Mousavi, S. M., Rahmani, J., Kord-Varkaneh, H., Sheikhi, A., Larijani, B., & Esmaillzadeh, A. (2020). Cinnamon supplementation positively affects obesity: A systematic review and dose-response meta-analysis of randomized controlled trials. Clinical Nutrition, 39(1), 123-133.

Zhang, C., Fan, L., Fan, S., Wang, J., Luo, T., Tang, Y., ... & Yu, L. (2019). Cinnamomum cassia Presl: A review of its traditional uses, phytochemistry, pharmacology and toxicology. Molecules, 24(19), 3473.