Keishi (Cinnamomum cassia)

Keishi (Cinnamomum cassia), known in Kampo medicine as cinnamon bark, contains the bioactive compound cinnamaldehyde along with cinnamic acid and procyanidins that drive its therapeutic effects. These compounds enhance insulin receptor signaling, activate GLUT4 translocation, and modulate vascular tone, supporting blood glucose regulation and endothelial health.

Origin & History

Keishi, also known as Cinnamomum cassia or Cinnamomi Cortex, originates from southern China and Southeast Asia. The bark is harvested from young trees, then air-dried or sun-dried for medicinal use.

Historical & Cultural Context

Keishi has been traditionally used in Kampo, a Japanese medical system, for treating fever, inflammation, and various gynecological conditions such as hypermenorrhea and dysmenorrhea.

Health Benefits

• Significant reduction in HbA1c levels in type 2 diabetes patients (PMID: 37262194).
• Decrease in blood glucose levels in type 2 diabetics (study mentioned, no PMID).
• Improvement in endothelial function in patients with climacteric syndrome (study mentioned, no PMID).
• Reduction in serum nonesterified fatty acids and oxidative stress markers in KBG trials (study mentioned, no PMID).
• Potential anti-inflammatory effects via COX-2 suppression (in-vitro studies).

How It Works

Cinnamaldehyde and A-type procyanidins in Cinnamomum cassia activate insulin receptor autophosphorylation and upregulate GLUT4 glucose transporter translocation to cell membranes, enhancing peripheral glucose uptake without increasing insulin secretion. Cinnamaldehyde also inhibits the enzyme protein tyrosine phosphatase 1B (PTP1B), which normally suppresses insulin signaling, thereby amplifying insulin sensitivity. Additionally, procyanidins act as antioxidants and modulate endothelial nitric oxide synthase (eNOS) activity, improving nitric oxide bioavailability and vascular function relevant to climacteric-related endothelial dysfunction.

Scientific Research

Clinical trials have shown that C. cassia can reduce HbA1c levels and improve endothelial function. Key studies include a randomized trial with 18 diabetic patients (PMID: 37262194) and trials involving Keishibukuryogan.

Clinical Summary

A randomized controlled trial (PMID: 37262194) demonstrated significant reductions in HbA1c levels in type 2 diabetes patients supplementing with Cinnamomum cassia extract, supporting its role as an adjunct glycemic management tool. Additional clinical data indicate measurable decreases in fasting blood glucose in type 2 diabetic populations, though several of these studies lack published PMIDs and have variable methodological quality. Clinical evidence also suggests improvement in endothelial function in women experiencing climacteric syndrome, and reductions in serum lipid fractions have been reported, though sample sizes across studies are generally modest. Overall, the evidence is promising but warrants confirmation through larger, well-controlled trials before definitive clinical recommendations can be made.

Nutritional Profile

Keishi (Cinnamomum cassia) bark is primarily valued for its bioactive compounds rather than conventional macronutrient content. Per 100g dried bark: carbohydrates ~80g (predominantly dietary fiber ~53g, with small amounts of starch and sugars), protein ~4g, fat ~1.2g, moisture ~10g, ash ~3.5g. Key micronutrients include manganese (~17.5mg/100g, 875% DV), calcium (~1002mg/100g), iron (~8.3mg/100g), potassium (~431mg/100g), magnesium (~60mg/100g), phosphorus (~64mg/100g), zinc (~1.8mg/100g), and vitamin K (~31.2mcg/100g). Primary bioactive compounds: (1) Cinnamaldehyde (trans-cinnamaldehyde): the dominant volatile constituent at 55–90% of essential oil content (~1–4% of dry bark weight), responsible for characteristic aroma and primary pharmacological activity; (2) Coumarin: present at relatively high concentrations in C. cassia (~0.45–6.97mg/g dry weight, significantly higher than Ceylon cinnamon), a key differentiator and safety consideration with an EFSA TDI of 0.1mg/kg body weight/day; (3) Cinnamyl acetate: ~3–8% of essential oil; (4) Type-A procyanidins (oligomeric proanthocyanidins): ~1–3% dry weight, implicated in insulin-potentiating activity via insulin receptor phosphorylation; (5) Cinnamic acid and derivatives: present at ~0.1–0.5% dry weight; (6) Eugenol: minor component ~1–5% of essential oil; (7) Polyphenols (total): ~8,000–12,000mg gallic acid equivalents/100g dry weight; (8) Methylhydroxychalcone polymer (MHCP): bioactive polyphenol that mimics insulin action. Bioavailability notes: cinnamaldehyde undergoes rapid first-pass metabolism to cinnamic acid; fat-soluble compounds (coumarin, cinnamaldehyde) have enhanced absorption with food; water-soluble polyphenolic fractions (type-A procyanidins) are the primary insulin-sensitizing agents in aqueous extracts; coumarin bioavailability is high (~72%) raising hepatotoxicity concerns at supplemental doses. Essential oil yield from bark: approximately 1–2% by steam distillation.

Preparation & Dosage

Clinically studied doses include 1000 mg of C. cassia three times daily (3 g/day total) and KBG formulations with a 7.5 g/day total dose. Consult a healthcare provider before starting any new supplement.

Synergy & Pairings

Ginger, turmeric, ginseng, licorice, green tea

Safety & Interactions

Cinnamomum cassia contains coumarin at concentrations that may pose hepatotoxic risk with prolonged high-dose use, distinguishing it from the lower-coumarin Ceylon cinnamon (C. verum); the European Food Safety Authority advises a tolerable daily intake of 0.1 mg/kg body weight for coumarin. Keishi can potentiate the effects of antidiabetic medications including metformin and insulin, increasing hypoglycemia risk, and caution is warranted with anticoagulants such as warfarin due to potential additive antiplatelet activity from cinnamaldehyde. Use during pregnancy is not recommended at therapeutic doses, as high amounts of cassia may stimulate uterine contractions, and individuals with liver disease should avoid supplementation due to coumarin load. Drug interactions with CYP450-metabolized medications are possible, as cinnamaldehyde has demonstrated in vitro modulation of CYP2C9 and CYP3A4 enzymes.