Cinnamon and Drug Interactions: What You Need to Know
Cinnamon is more than just a spice. In Eastern medicine, cinnamon twig (Keishi or Gui Zhi in Traditional Medicine) plays a key role in traditional herbal practices and is widely used to warm the body, support digestion, and improve circulation. It’s not uncommon for patients to regularly consume cinnamon-based formulas alongside prescription medications.
A recent study in Food Chemistry on ScienceDirect highlights that high doses of cinnamon, especially in supplement or oil form, may interact with medications by altering how the body metabolizes them.
What the Study Found
Researchers studied cinnamaldehyde, the main active compound in cinnamon, and found that:
- Cinnamaldehyde is 100% bioaccessible, it means if you ingest it (like from cinnamon oil), your body absorbs nearly all of it.
- It’s quickly metabolized in the liver into cinnamic acid.
- Cinnamon oil, rich in cinnamaldehyde, was shown to activate drug-metabolizing receptors (PXR and AhR) in the liver and intestines.
- These receptors (PXR and AhR) influence how medications are broken down, potentially affecting its strength or duration.
- Cinnamon oil and cinnamaldehyde also inhibited important liver enzymes (CYP2C9 and CYP1A2), raising the possibility of herb-drug interactions.
Why This Matters
Cinnamaldehyde, the main active compound in cinnamon, isn’t necessarily harmful—it also offers many beneficial effects and is considered safe in typical amounts, such as those found in food or professionally prescribed herbal formulas.
However, high doses of cinnamaldehyde may affect how the body processes medications by interacting with drug-metabolizing enzymes and receptors. This can change the strength or duration of certain drugs. It’s especially important for people taking medications for:
- Diabetes,
- Hypertension
- Autoimmune disorders
- Mental health conditions
Cinnamon can be helpful, but when concentrated, it deserves caution.
How Much Cinnamon is Too Much?
Cinnamon is widely used as both a spice and a medicinal herb. But not all cinnamon is created equal, especially when it comes to its active compounds.
Cinnamon contains two key compounds: cinnamaldehyde, which contributes to its benefits but may affect how the body metabolizes medications when taken in concentrated forms, and coumarin, which can harm the liver if consumed in high amounts.
Coumarin and cinnamaldehyde levels vary depending on the type of cinnamon:
- Cassia Cinnamon, the most common and affordable type of cinnamon, is known for its strong, spicy flavor. It contains high levels of cinnamaldehyde (~9.5–19 mg/g) and significant amounts of coumarin (~3–5 mg/g), which may exceed safe daily intake with regular use. Best used in moderation due to potential liver and drug interaction risks.
- Ceylon Cinnamon, often called “true” cinnamon, is milder and more aromatic. It contains lower levels of cinnamaldehyde (~2.5–6.3 mg/g) and virtually no coumarin (<0.0004 mg/g), making it a safer option for regular use. While more expensive and less widely available, it is valued for its purity and lower risk profile.
| Type | Oil in Bark | Cinnamaldehyde in Oil | Cinnamaldehyde (mg/g) | Coumarin (mg/g) | Notes |
|---|---|---|---|---|---|
| Cassia | 1–2% | ~95% | ~9.5–19 | ~3–5 | Strong flavor; high coumarin |
| Ceylon | 0.5–1% | 50–63% | ~2.5–6.3 | <0.0004 | Mild; low coumarin |
Children Should Have Even Less
Children should consume no more than 0.5 g per day, based on body weight, as they are more sensitive to coumarin.
| Cassia Cinnamon (max) | Ceylon Cinnamon (typical use) | |
|---|---|---|
| Adults | Up to 2g/day (1 tsp) | 0.6–3g/day is generally safe |
| Children | 0.5g/day or less | ~Half of adult dose recommended |
Safety and Considerations in Eastern Medicine
In Kampo medicine, cinnamon is a common ingredient used in many formulas. While Ceylon cinnamon is rarely used, Cassia cinnamon is often prescribed in traditional formulas.
Both cinnamon bark and cinnamon twig are derived from the Cinnamomum cassia tree, but they serve distinct therapeutic purposes depending on the condition being addressed in Kampo medicine.
- Cinnamon twig (Keishi/桂枝) is harvested from young twigs and is considered warm and gentle. It’s commonly used to release the exterior, promote sweating, improve circulation, and support digestion—making it ideal for early-stage colds or mild symptoms. It typically contains less coumarin than cinnamon bark, making it preferred for gentler applications.
- Cinnamon bark (Nikkei/肉桂) comes from the tree’s inner bark and is much hotter in nature. It’s used to warm the interior, tonify Kidney Yang, and dispel deep cold, often prescribed for chronic fatigue or cold extremities. However, due to its intensity, it should be used with caution in individuals prone to heat.
From an Eastern medicine perspective, cinnamon offers therapeutic benefits that depend on its preparation and application. While the dosage of herbal formulas varies by prescription, 1.2 g of this Keishi (Gui Zhi) extract (equivalent to 9 g of raw herb) is generally considered safe for short- to moderate-term use. Based on typical cinnamaldehyde content in cinnamon twig, this dosage falls within the WHO’s recommended safety limits.*
For long-term or high-dose use, professional guidance and monitoring are strongly recommended.
