Cassia is one of the most widely used spices in the world, though most people know it simply as “cinnamon.” The cassia bark sold in grocery stores across North America, sourced primarily from Cinnamomum cassia trees grown in southern China, Vietnam, and Indonesia, serves as a cooking spice, a traditional medicine ingredient, and a source of essential oil for aromatherapy. Separately, plants in the Cassia/Senna genus are the source of one of the most common over-the-counter laxatives. Here’s how each form of cassia is actually used.
Cassia as Everyday Cinnamon
If you’ve bought ground cinnamon in North America, you’ve almost certainly bought cassia. Retailers rarely distinguish between cassia and Ceylon cinnamon (the milder, more expensive variety from Sri Lanka), so cassia dominates supermarket shelves. It has a bolder, more pungent flavor than Ceylon, which is exactly why food manufacturers prefer it.
Cassia bark flavors baked goods, hot drinks, cereals, and chocolate. It’s also a key ingredient in Chinese five-spice powder alongside fennel, cloves, star anise, and Sichuan pepper. Liqueurs and spiced beverages rely on cassia for that recognizable warm, sweet bite. In most commercial kitchens and packaged foods, cassia is the default “cinnamon.”
Blood Sugar and Cholesterol Support
Cassia cinnamon has drawn serious research interest for its effects on blood sugar. In a well-known clinical trial published in Diabetes Care, 60 people with type 2 diabetes took either 1, 3, or 6 grams of cinnamon daily for 40 days. All three doses reduced fasting blood glucose by 18 to 29 percent. The same groups saw drops in triglycerides (23 to 30 percent), LDL cholesterol (7 to 27 percent), and total cholesterol (12 to 26 percent). The placebo groups showed no significant changes.
These results suggest that even small amounts of cassia cinnamon, as little as 1 gram (roughly half a teaspoon), can meaningfully influence metabolic markers in people with type 2 diabetes. That said, cassia isn’t a replacement for diabetes medication. It’s better understood as a dietary addition that may offer modest metabolic benefits over time.
A Cornerstone of Chinese Medicine
Cassia holds a special place in traditional Chinese medicine, where it has been used for nearly two millennia. The Shanghan Lun, one of China’s most revered herbal texts written about 1,850 years ago, opens its introduction of classical prescriptions with a cinnamon-based formula. That’s not an accident. Cassia is considered a symbol of “yang qi,” the body’s warming, activating energy.
Practitioners use two distinct parts of the plant. The twigs (called Guizhi) are associated with a circulating, mobilizing effect and were the original medicinal form. The bark (Rougui) entered medical use later, around the 7th or 8th century, and is considered more of a tonic that strengthens deep reserves of warmth and vitality. Both are prescribed for cold sensations, poor circulation, digestive sluggishness, low energy, and immune support.
What makes cassia unusual among warming herbs in Chinese medicine is its dual ability: it’s said to both clear out stagnation and build up the body’s reserves at the same time. Most pungent herbs do one or the other, which is why classical texts valued cassia so highly for long-term use in chronic conditions.
Cassia Senna as a Laxative
The word “cassia” also refers to plants in the Senna genus, and this is an entirely different use. Senna leaves and pods contain compounds called sennosides, which are the active ingredients in many over-the-counter laxatives.
Sennosides work by being converted into an active compound in the gut that triggers two things simultaneously. First, it slows contractions in the upper colon, reducing water absorption so stool stays softer. Second, it speeds transit through the lower colon by activating immune cells in the colon wall, which release a signaling molecule that further blocks water reabsorption. The combined effect is faster, easier bowel movements, typically within 6 to 12 hours of taking a dose. Senna-based laxatives are among the most commonly used stimulant laxatives worldwide.
Cassia Essential Oil
Cassia essential oil, distilled from the bark, has a warm, spicy scent that’s popular in aromatherapy, especially during colder months. Diffusing a few drops creates an atmosphere that many people find calming and comforting. Some aromatherapy practitioners recommend it for stress relief and relaxation.
Topically, diluted cassia oil is used as a circulation booster. It creates a noticeable warming sensation on the skin, which is why it shows up in muscle-soothing blends. Some people add a couple of drops to bathwater for a combination of skin refreshment and relaxation. The oil also works as a mild astringent in skincare, where it’s used to tighten and brighten the appearance of skin. Because cassia oil is potent, it should always be diluted with a carrier oil before skin contact to avoid irritation.
Coumarin: The Safety Concern
The one serious consideration with cassia cinnamon is its coumarin content. Coumarin is a naturally occurring plant compound that, in high doses over time, can stress the liver. Cassia cinnamon contains between 1,880 and 3,260 milligrams of coumarin per kilogram, roughly 100 times more than Ceylon cinnamon, which tops out around 185 mg/kg.
The European Food Safety Authority has set a tolerable daily intake of 0.1 mg of coumarin per kilogram of body weight. For a 70-kilogram (154-pound) adult, that works out to 7 mg per day. Depending on the specific cassia product, you could hit that limit with just a teaspoon or two of ground cinnamon. At typical culinary amounts (a sprinkle on oatmeal, a dash in coffee), cassia is considered safe. Problems arise when people take large daily doses as a supplement, especially over weeks or months.
There’s at least one documented case of a patient developing acute liver inflammation after combining a cinnamon supplement with a cholesterol-lowering statin medication. If you take medications that are processed by the liver and want to use cassia cinnamon regularly in supplement-sized doses, that combination warrants caution. For heavy or long-term cinnamon use, switching to Ceylon cinnamon significantly reduces coumarin exposure.
The National Institutes of Health notes that cassia cinnamon in normal food amounts is likely safe, but larger or prolonged doses are sometimes associated with gastrointestinal problems or allergic reactions. The coumarin content varies widely between products, so “cassia cinnamon supplement” on a label doesn’t tell you exactly how much coumarin you’re getting.