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Cinnamon is pleasant, easy to take and does one thing well. These are the questions our naturopaths ask in store, and most of them come down to Ceylon or cassia.

A good fit if

• Your blood sugar is drifting high and you're managing it with your doctor
• You're happy with a plain spice dose of a few grams rather than an extract
• You'll choose Ceylon if you're taking it every day
• You'd like to hear plainly that the trial results vary and that the Cochrane review found the evidence insufficient

Check with us first if

• You take diabetes medicine or insulin. Cinnamon has a measurable effect on blood glucose, and you shouldn't adjust your medicine yourself.
• You're buying for a child. The coumarin limit is much lower for children, and cold and flu uses must carry an adults-only or under-2 warning on the label.
• You already eat a lot of cassia, so we can work out where you sit against the coumarin limit.
• You've had burning or swelling in your mouth from cinnamon flavouring. This is called contact stomatitis.
• You have liver disease, because the known harm from coumarin is to the liver.
• You're pregnant or breastfeeding. We don't have any evidence either way.

• Ceylon or true cinnamon bark (item 1390). Best known for: Everyday use, and use by children. Absorption: When used as an active, coumarin is a required component, capped at 0.001% of the medicine. Typical use: Lower in coumarin than cassia. Germany's federal risk assessment institute advises people who have cinnamon often to choose it.
• Cassia bark, dry and powder (items 1232 and 1233). Best known for: The common dark cinnamon in supermarkets. Absorption: Item 1233 is the only one that ties the 0.001% coumarin limit to the medicine's maximum daily dose. Typical use: Most of the older blood sugar trials used cassia, at an average of about 2 g a day. Higher coumarin is the trade-off.
• Cinnamon powder and cinnamon dry (items 1392 and 1394). Best known for: The item names most listed capsules come under. Absorption: Cinnamon bark oil is a required component, capped at 2% of the product. Typical use: Whole-spice doses of 1 to 6 g a day, which is where most of the trial evidence sits.
• Concentrated bark extract. Best known for: More polyphenols per capsule. Absorption: The solvent matters. A water-and-alcohol extract did better than a water-only one on short-term glucose. Typical use: 250 mg to 1 g a day in trials. The coumarin limit still applies to the finished medicine.
• Water or aqueous extract. Best known for: Simpler to make. Absorption: One water extract was high in phenols and antioxidant capacity but had no short-term effect on glucose. Typical use: 2.4 g a day of a cassia water extract changed gut transit over 8 weeks.
• Cinnamon tea or infusion. Best known for: The everyday form. Absorption: The dose is not controlled. Typical use: In one trial a 2 g tea actually made people feel less full and eat more at the next meal. Don't expect the capsule findings to carry over.
• Cinnamon bark oil (item 1391). Best known for: Flavour, fragrance and skin products. Absorption: Capped at 2% of the product. Typical use: Not something you take by mouth. Undiluted bark oil is not a consumer product.
• Cinnamon leaf oil (item 1393). Best known for: The strictest packaging rules in the family. Absorption: Not for internal use. Typical use: Above 25% strength it needs a container no bigger than 25 mL, a restricted flow insert, and the warnings "Keep out of reach of children" and "Not to be taken".
• Isolated cinnamaldehyde (item 1386). Best known for: The compound behind cinnamon's smell. Absorption: Does not apply. Typical use: Allowed only as a flavour or fragrance (excipient), never as an active. It is also the compound behind contact stomatitis, a reaction in the mouth.
• Cinnamomum camphora (item 1388). Best known for: Camphor laurel, a different species entirely. Absorption: Does not apply. Typical use: Camphor, cineole and safrole are its required components. It is not cooking cinnamon and should not be confused with it.

Reference values. There's no recommended intake for cinnamon. It's a spice and a herb, not a nutrient.

Typical supplemental range. Trials of the whole spice used 1 to 6 g a day, with an average of around 2 g across the blood sugar studies. Trials of extracts used 250 mg to 1 g a day for 12 weeks to 4 months.

Upper level. No cinnamon entry on Australia's permitted ingredients list (Schedule 1) sets a maximum daily dose. The limit that really matters is for coumarin: a tolerable daily intake of 0.1 mg per kg of body weight. A 60 kg adult reaches that at roughly 2 g a day of cassia with average coumarin levels. Going over for a short time isn't the worry. European authorities say three times the tolerable intake for one to two weeks isn't a safety concern. Regular high intakes of cassia are.

Worth knowing. For occasional cooking, either type is fine. If you're taking a supplement-sized dose every day, buying for a child or already eat a lot of cinnamon, choose Ceylon, or a listed medicine, where coumarin is capped for you at 0.001%. What you need depends on your age, diet and health, so talk to one of our naturopaths in store.

Food first, where the diet allows it.

• Ground cinnamon and quills from the spice aisle: sold as food, so none of the Schedule 1 coumarin ceiling or container rules apply to them
• Cassia in baked goods: A 15 kg child reaches the coumarin tolerable intake at about 30 g of cinnamon stars or 100 g of gingerbread a day
• Cinnamon tea: A food, with an uncontrolled dose. The capsule findings don't transfer to it

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• Coumarin is the main safety issue with cinnamon, and it is more a food problem than a medicine one. The tolerable daily intake is 0.1 mg per kg of body weight. A 60 kg adult reaches it at about 2 g of average cassia a day, and a 15 kg child at about 0.5 g. Cassia has significantly more coumarin than Ceylon. In sensitive people, even fairly small amounts of coumarin have caused liver damage.
• To put that in perspective, so you are not alarmed: European authorities say three times the tolerable level for one to two weeks is not a safety concern. A fortnight of spiced food is not the issue. Eating a lot of cassia every day is.
• Children. The coumarin limit depends on body weight, so it is much lower for them. Cinnamon cold claims must also carry the label statement "Adults only, OR Not to be used in children under 2 years of age without medical advice".
• You take diabetes medicines. Our sources have no documented interaction, but cinnamon measurably lowers fasting and after-meal glucose in people with diabetes. Tell your doctor or pharmacist before adding it, and don't change your medicine yourself.
• Mouth and lips. Cinnamon is a known cause of contact stomatitis, with burning, swelling and redness. One published case from chewing gum was mistaken for facial swelling (angioedema).
• Concentrated cinnamon leaf oil. Above 25% strength, the law requires a container no bigger than 25 mL, a restricted flow insert, and the warnings "Keep out of reach of children" and "Not to be taken". Above 15 mL it also needs a child-resistant lid. These rules are there to prevent poisoning.
• Mixing it up with camphor laurel. Cinnamomum camphora is a different species, with camphor, cineole and safrole as required components, and safrole capped at 0.1% for internal use. It is not cinnamon.
• You take warfarin. This is unresolved. A review listing 78 herbs and foods reported to interact with warfarin did not name cinnamon, but we won't treat that as an all-clear. Ask your prescriber.
• Pregnancy and breastfeeding. No trial or review in our sources looked at either.
• Liver. Reassuringly, two reviews of randomised trials found no effect on ALT, AST or ALP at trial doses and lengths. That does not tell us about years of eating a lot of cassia.