Stack Genius ingredient guide
Cinnamon
The inner bark of Cinnamomum trees, sold either as culinary spice or as a supplement marketed for blood sugar and metabolic support.
Overview
Cinnamon comes from the inner bark of several trees in the Cinnamomum genus. In supplements, the two species that matter are Ceylon (Cinnamomum verum, sometimes called "true cinnamon") and cassia — a group that includes Cinnamomum cassia, aromaticum, and burmannii. Most of what you find in a U.S. grocery store spice jar is cassia, not Ceylon.
In supplement form, cinnamon is most often marketed for blood sugar and metabolic support, sometimes alongside chromium or berberine. Small trials have looked at effects on fasting glucose and lipids in people with type 2 diabetes or metabolic syndrome, with modest and inconsistent results. It is also used in general "antioxidant" or "anti-inflammatory" formulas because of its polyphenol content.
The important nuance is coumarin: cassia cinnamon is naturally high in coumarin, a compound that can stress the liver at high sustained intakes. That is why the Ceylon-versus-cassia distinction shows up on serious cinnamon supplement labels and matters for anyone using it daily.
Key takeaways
- Ceylon cinnamon (Cinnamomum verum) is far lower in coumarin than the more common cassia varieties.
- Evidence for blood sugar effects is modest and inconsistent; cinnamon does not replace diabetes medications.
- Long-term high-dose cassia use raises liver concerns, especially in people with liver disease or on other hepatotoxic drugs.
Practical guidance
What to know before adding Cinnamon
Evidence snapshot
Meta-analyses of cinnamon in type 2 diabetes and prediabetes show small reductions in fasting blood glucose and modest changes in lipids, but effects are inconsistent across trials and vary by species and extract type. It is not a replacement for medication or lifestyle change. Evidence for polycystic ovary syndrome, cognitive function, and antimicrobial uses is early and limited.
What to look for on the label
Look for the species name — Cinnamomum verum for Ceylon or Cinnamomum cassia/aromaticum/burmannii for cassia — right on the label, not just "cinnamon." For daily supplement use, Ceylon or a certified low-coumarin extract is the safer choice. If a product uses cassia and does not disclose coumarin content, treat that as a data gap.
What makes a better product
A better product names the species, provides the plant part (bark), states a specific extract ratio or standardized polyphenol content, and ideally publishes coumarin testing. Water-based extracts remove much of the coumarin content and are used in some clinical trial products. Third-party testing for heavy metals is worthwhile because bark extracts can concentrate contaminants.
Watch-outs
Long-term daily use of high-dose cassia cinnamon can exceed safe coumarin thresholds and stress the liver, especially in people with existing liver disease. Cinnamon may lower blood sugar, so people on insulin or sulfonylureas should monitor for hypoglycemia. Contact allergy to cinnamaldehyde can cause mouth irritation. Not enough safety data supports high-dose supplement use during pregnancy.
Dosing & Timing
Clinical trials commonly use 1 to 6 grams of cinnamon per day, though many effective-looking studies cluster around 1 to 3 grams daily, split with meals. Concentrated extracts use much smaller amounts to deliver comparable actives. For daily use, staying at the lower end and choosing Ceylon or a low-coumarin extract reduces long-term liver risk.
Safety and interaction context
The main safety concern is coumarin content in cassia, which at sustained high intakes has been linked to hepatotoxicity, particularly in people with underlying liver disease. Cinnamon may enhance the glucose-lowering effect of diabetes medications, and it may modestly affect platelet function, adding some caution when combined with blood thinners. Mouth irritation and contact dermatitis are the most common side effects of concentrated cinnamon products. Avoid high-dose supplement use during pregnancy and breastfeeding.
Sources
- NCCIH — CinnamonEvidence review including coumarin considerations.
- Memorial Sloan Kettering About Herbs — CinnamonClinical uses and interactions.
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