We mostly see them as flavorants, as the little jars of powder that line our cabinets and the bags of dried roots, barks, and leaves tucked away in drawers, designed to subtly or drastically alter the flavor profile of our “smart fuel” creations in the kitchen, but for most of human history, spices were also prized for their medicinal qualities. Turmeric for GI disorders and inflammation. Chili peppers for pain management. Ginger for diarrhea. These aren’t just exaggerated cases of “folk medicine” or “old wives’ tales,” either. Current research has confirmed that many common spices do indeed have medicinal properties. One of the most beneficial is also the most common: cinnamon.

It’s important to realize that there are multiple varieties of cinnamon.

There’s Ceylon cinnamon, or “true cinnamon,” or cinnamomum zeylanicum. Ceylon cinnamon comes from the crumbly inner bark of the cinnamomum zeylanicum tree, and its flavor is sweet and delicate. It is light brown. You should be able to snap a stick of real cinnamon in half quite easily. If you’ve ever had cinnamon candies, that’s real Ceylon you’re tasting.

There’s Cassia, or cinnamomum aromaticum. It’s usually sold as cinnamon in the United States. Recipes calling for cinnamon can use cassia instead without issue, but cassia has a harsher, more overpowering flavor with less sweetness and more brute force. It is a darker, redder brown. Cassia sticks are rather hardy.

There’s also Saigon cinnamon, or cinnamomum loureiroi. Saigon cinnamon is the most prized member of the Cassia family. It has a full, complex flavor with even less sweetness. Saigon cinnamon is generally pretty expensive.

As for the purported health benefits of cinnamon consumption, you’d think that “true cinnamon” is best. I mean, it’s the real stuff, right? A quick look across the web seems to confirm that suspicion, with most references you’ll find on message boards and herbal medicine sites imploring you to “get real Ceylon cinnamon, not that Cassia crap.” But what’s the reality? Does “true” necessarily indicate “better”?

Well, let’s look at the possible benefits of cinnamon consumption, as well as the chemical component that appears to be responsible. Most researchers have focused on cinnamaldehyde, the organic compound that gives cinnamon its signature flavor. Hold on to your seat. We’re about to get a little technical.

Cinnamaldehyde’s benefits include:

Rather than merely mask a person’s bad breath, cinnamaldehyde in cinnamon-flavored chewing gum actually exerts an antimicrobial effect on the tongue bacteria that cause bad breath.

In human melanomas grafted onto mice, orally-administered cinnamaldehyde impaired cancer cell proliferation, invasiveness, and tumor growth.

Cinnamaldehyde, by (derived from Cassia bark, in fact) activating a protective antioxidant effect in human epithelial colon cells, evinced potential chemoprevention against colon cancer.

Cinnamon oil, most of which is cinnamaldehyde, is an effective insect repellant with the ability to specifically target and kill mosquito larvae.

Cinnamaldehyde was shown to decrease HbA1c, total cholesterol, and triglyceride levels while increasing plasma insulin, hepatic glycogen, and HDL levels. The oral dosage used – 20mg/kg body weight – wasn’t an unrealistic amount.

Cassia may help relieve the muscular insulin resistance that occurs following a bad night’s sleep.

Although it’s “cinnamon oil” that kills bugs and something with “cinnamon” practically right there in the name itself may fight cancer, “fake” cinnamon actually contains more cinnamaldehyde than “true” cinnamon. That’s right – Cassia oil has the most cinnamaldehyde.

In another study, researchers using both Cassia extract and Ceylon extract found that the Cassia was more effective in diabetic rats observed in a glucose tolerance test.

Remember c. elegans, those plucky roundworms whose lifespan increased with both intermittent fasting and glucose restriction (the glucose study’s author, Cynthia Kenyon, has even adopted a low-carb diet in light of the results), and which have been deemed suitable models for the study of glucose restriction in higher mammals? Cassia bark had a similar effect on them, too.

That’s not to say that Ceylon doesn’t have its benefits, too:

One study showed that cinnamon oil extracted from Ceylon bark reduced early stage diabetic nephropathy, or kidney disease. This particular oil was high (98% by volume) in cinnamaldehyde.

An aqueous solution of Ceylon cinnamon bark inhibited two common hallmarks of Alzheimer’s disease: tau aggregation and filament formation. Researchers isolated an A-linked proanthocyanidin (a type of polyphenol) and determined it handled the lion’s share of tau aggregation inhibition, with cinnamaldehyde possibly responsible for a fraction of it. Of the cinnamon varieties, only Ceylon carries the proanthocyanidin.

Another Ceylon isolate, a proanthocyanidin called proanthocyanidin B1, was shown to mimic – and even surpass – the effect of insulin in certain fat tissues (PDF). This particular proanthocyanidin only occurs in three places: Ceylon cinnamon bark, cat’s claw root, and the leaf of the common grape vine.

There have been mixed views on cinnamon’s efficacy in diabetic patients. One study found little overall average difference between lab results in type 2 diabetic patients given either 1.5g/d Cassia powder or placebo, although the Cassia patients enjoyed slightly larger drops in HbA1c with some experiencing more drastic reductions. The study’s authors didn’t find it statistically significant, but the results may suggest that certain individuals may be especially responsive to Cassia/Ceylon. At any rate, it’s worth trying, because people are not statistics, and the average/mean isn’t everything. Some people improved markedly, even though statistical analysis showed little difference. Any benefits in glucose tolerance and insulin sensitivity, another study noted, are also short-lived, making steady intake necessary for lasting effects.

Note that Cassia contains significant amounts of coumarin, which humans metabolize to 7-hydroxycoumarin, a toxin moderately damaging to the liver and kidneys. Rodents metabolize it to 3,4-coumarin epoxide, a highly toxic compound, making coumarin a common ingredient in rodenticides. A teaspoon of Cassia cinnamon powder contains 5.8 to 12.1 mg of coumarin and, according to the European Food Safety Authority, the tolerable daily intake for humans is 0.1mg/kg body weight, meaning a daily teaspoon might exceed the limit for smaller individuals. The German Federal Institute for Risk Assessment has gone on record in cautioning against high daily intakes of coumarin (PDF).

In the end and for all their differences, Ceylon and Cassia are actually pretty similar (similar enough to pass for each other, for one!). They both have potent pharmacological benefits, and they’re both delicious in curries, coconut milk, coffee, and – my personal favorite when I eat them – on sweet potatoes or yams. If it’s cinnamaldehyde you’re after, the general rule is that the sweeter the cinnamon, the more concentrated the cinnamaldehyde (although ultra-concentrated doses grow more pungent). There are valid concerns with the amount of coumarin in Cassia, making daily usage of therapeutic doses questionable. Ceylon contains negligible amounts of coumarin, but its blood glucose benefits don’t seem to be as potent as Cassia’s. In my opinion, using both while never straying too far over 1 teaspoon of Cassia per day (larger individuals can go higher) is a good, safe bet.

One possible way to avoid coumarin and still eat Cassia is to make hot tea. From what I could gather online, coumarin is fat-soluble only, meaning steeping Cassia in hot water, broth (fat skimmed), or tea could extract the beneficial compounds and leave out the coumarin. Just strain the solids and drink. It may also be that traditional usage of cinnamon utilized the whole bark form, rather than the powder. Folks may not have been actually consuming the cinnamon solids, but it’s difficult to know. I assume steeping a big piece of Cassia in a pot of curry or other fatty stew would extract plenty of coumarin, provided it’s indeed fat-soluble. Either way, it’s not going to kill you unless you’re consuming heaps and heaps of Cassia powder. I suppose if you’re really worried about it, you could try one of the commercial cinnamon water-extractions on the market, but I’m usually a fan of food-based “supplementation” as long as the supplement in question exists in appreciable amounts in whole food – which they certainly do in this case.

Ah, what to use, how to extract it, and how much to consume? – the eternal question facing us students of health and optimal nutrition. Just eat, steep, grind, or cook with it, and you’ll be fine.

Written by Mark Sisson for Mark’s Daily Applr, May 18, 2015.

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