Cinnamon bark is the dried inner bark of trees in the Cinnamomum genus, peeled from young shoots and rolled into the familiar tubes (called quills) you find in spice racks worldwide. It’s one of the oldest traded spices, and what most people think of as “cinnamon sticks” are literally strips of tree bark that have been scraped, curled, and dried. The spice comes in two main varieties with meaningful differences in flavor, chemistry, and safety.
Which Part of the Tree Becomes Cinnamon
Cinnamon trees are regularly cut back to encourage new shoots, a technique called coppicing. Workers harvest these young shoots by making a clean cut at a 45-degree angle about two inches above the ground. The outer bark, which is rough and brown, gets scraped off. Then the inner bark is loosened by rubbing the stem with a brass rod until the sap oozes out and separates the bark from the wood beneath.
Once loosened, the inner bark is peeled away in long strips using a small knife. These strips naturally curl inward as they dry, forming the tight, scroll-like quills sold as cinnamon sticks. Thinner strips and fragments that break off during peeling are graded separately and often ground into powder. The entire process, from cutting the shoot to producing a finished quill, is still done largely by hand in the major producing countries.
Ceylon vs. Cassia: Two Different Spices
Most cinnamon on grocery shelves is cassia cinnamon, harvested from Cinnamomum cassia trees grown primarily in China, Indonesia, and Vietnam. It has a bold, slightly sharp flavor and produces thick, hard quills with a single curled layer. Ceylon cinnamon, from Cinnamomum verum trees grown mostly in Sri Lanka, is lighter in color, milder in taste, and forms delicate quills with many paper-thin layers rolled together.
The chemical profiles are quite different. Ceylon bark oil contains roughly 50 to 63% cinnamaldehyde, the compound responsible for cinnamon’s signature warm, spicy taste. Cassia bark oil is nearly 95% cinnamaldehyde, which explains its more intense flavor. Both barks contain dozens of other volatile compounds, but the concentration of cinnamaldehyde is the biggest driver of how they taste and smell. Essential oil yield from cassia bark ranges from about 0.4% to 3.1% by weight, depending on the age and part of the tree.
The distinction that matters most for regular consumers is coumarin, a naturally occurring compound that can stress the liver in high amounts. Cassia cinnamon contains up to 1% coumarin, with tested samples averaging between 2,650 and 7,017 milligrams per kilogram. Ceylon cinnamon contains only a trace (about 0.004%), and samples from Sri Lanka have tested as essentially coumarin-free. If you sprinkle cinnamon on your oatmeal once in a while, this difference is irrelevant. If you consume cinnamon daily in larger amounts, Ceylon is the safer long-term choice.
What Gives Cinnamon Its Properties
Beyond cinnamaldehyde, cinnamon bark is rich in polyphenols. Lab analysis of Ceylon bark extract found a total polyphenol content of about 520 micrograms per milligram of powder, with flavonoids making up a large share. Specific compounds identified include vanillic acid, caffeic acid, ferulic acid, cinnamic acid, and catechins. These are the same families of antioxidant compounds found in green tea, berries, and dark chocolate, though in different proportions.
Cinnamaldehyde is also what gives cinnamon bark its mild antimicrobial reputation. It disrupts the cell membranes of certain bacteria and fungi, which is why cinnamon was historically used as a food preservative long before refrigeration existed.
Cinnamon Bark and Blood Sugar
The most studied health angle for cinnamon bark is its effect on blood sugar. Cinnamon extract slows the digestion of starches and sugars by blocking an enzyme in the small intestine that breaks carbohydrates into glucose. This means sugar enters the bloodstream more gradually after a meal rather than in a sharp spike. Cinnamon also appears to help cells respond more effectively to insulin.
Clinical trials have tested daily doses ranging from 500 milligrams to 6 grams in people with type 2 diabetes and metabolic syndrome. Results are mixed but lean positive. In one study of 60 patients, just 1 gram of ground cinnamon per day for 40 days improved fasting blood glucose and blood lipid levels. A 90-day trial found that 1 gram daily significantly reduced a long-term blood sugar marker. Other trials using 1.5 to 2 grams per day over 12 weeks showed similar modest improvements.
Not every study found benefits. Some trials using 500 milligrams twice daily for three months showed no significant effect compared to a placebo. The general pattern from the research is that at least 1 to 2 grams per day for one to two months is the minimum needed to see any measurable impact, and even then, the effects are modest supplements to, not replacements for, standard blood sugar management.
Common Forms and Uses
Cinnamon bark is sold as whole quills, ground powder, essential oil, and capsule supplements. Whole quills are used to infuse flavor into liquids like tea, mulled wine, and braised dishes. Ground cinnamon is what goes into baked goods, curries, and spice blends. The essential oil is highly concentrated and used in aromatherapy and flavoring but should never be consumed undiluted.
In traditional medicine systems across South Asia, the Middle East, and China, cinnamon bark has been used for centuries to treat digestive complaints, respiratory infections, and menstrual discomfort. Modern research has focused almost exclusively on its metabolic effects, particularly blood sugar and cholesterol, leaving many of these traditional uses without strong clinical evidence.
How to Choose Between Types
If you’re buying cinnamon sticks, the difference is easy to spot. Ceylon quills are tan, fragile, and made of many thin layers you can crumble with your fingers. Cassia quills are dark reddish-brown, thick, and hard enough that you’d struggle to break them by hand. Ground cinnamon is harder to distinguish visually, but the label or country of origin helps: Sri Lanka almost always means Ceylon, while China, Vietnam, or Indonesia means cassia.
For occasional cooking, either type works fine and the choice comes down to flavor preference. Cassia is bolder and pairs well with heavy baking and savory dishes. Ceylon is subtler and better suited to delicate desserts and drinks. For daily use in larger quantities, particularly if you’re taking cinnamon for its potential metabolic effects, Ceylon’s negligible coumarin content makes it the more practical option.