Cinnamomum cassia

What is Cinnamomum cassia?

Cassia is the dried inner bark of Cinnamomum cassia, an evergreen tree from south China and Southeast Asia. It is the common "cinnamon" sold in most shops. Most ground cinnamon in the United States and Asia is cassia, not Ceylon cinnamon.

In Chinese medicine the thick bark is called rou gui. The thin young twigs are called gui zhi. Both were used as warming remedies for many centuries.

Today it is sold as a kitchen spice, as tea and as capsules. The best-studied modern use is blood sugar in type 2 diabetes.

The short verdict: human trials show small, uneven blood sugar effects and little else. Long use in tradition is not proof that a remedy works, and it is not proof that it is safe.

How does Cinnamomum cassia work?

Most of what we know about how cassia acts comes from lab and animal work, not from people.

Cassia bark is rich in cinnamaldehyde. In cell and animal studies, cinnamaldehyde appears to help cells take up sugar. It seems to act on the insulin signal inside the cell.

In test tubes, cassia extracts slow enzymes that break down starch. That could blunt the sugar rise after a meal. Whether this matters much in people is not clear.

Lab tests also show it slows some bacteria and yeasts. That does not mean it treats an infection in the body.

In people, the measured effect on blood sugar is small and not steady. Many trials show little or no change in HbA1c, a three-month blood sugar score.

What forms does Cinnamomum cassia come in?

Cassia is sold mostly as a kitchen spice. Supplement forms are stronger and carry more coumarin per dose.

Common forms: - Ground bark powder - Rolled bark quills, sold as sticks - Capsules of ground bark - Water extracts, often labelled as low in coumarin - Teas and decoctions, used in Chinese medicine - Tinctures made with alcohol - Essential oil, for scent only

The oil is very strong. It can burn skin, lips and the gut lining. It is not a form to swallow.

Where it comes from:

Cassia has been used in China for well over two thousand years. The bark was listed in the Shennong Bencao Jing, an early herbal text.

Healers called the thick bark rou gui and the thin twigs gui zhi. Rou gui was given for "cold" patterns deep in the body. Gui zhi appeared in classic formulas for chills, fever and aching limbs.

Cassia also travelled along old trade routes to Egypt, Greece and Rome. It was prized as a spice, a perfume and an embalming material.

What does Cinnamomum cassia help with?

• Blood sugar in type 2 diabetes: This is the most studied use, and the evidence is weak. Pooled trials show fasting blood sugar falling by a few points. Effects on HbA1c, a three-month blood sugar score, are mixed. Trials were small and short. They used different species, doses and extracts. Cassia is not a swap for diabetes medicine.
• Blood fats, such as cholesterol and triglycerides: Some trials report small drops in total cholesterol and triglycerides. Others report no change at all. The pooled effect is too small and too uneven to rely on. Diet, exercise and prescribed drugs do far more.
• Bloating and poor appetite: Warming spices were traditionally given for a weak or cold stomach. Cassia was one of them. There is almost no human trial evidence for this use. Many people simply find the taste settling after a meal.
• Period pain: Cinnamon has been tested in a few small trials in young women. Some reported less pain and bleeding. The trials were small and of low quality. This use should be called unproven.
• Chills and early colds, in Chinese medicine: Gui zhi, the twig, was used in formulas for chills, stiff neck and early fever. It was rarely given alone. No good modern trials test cassia for colds. Tradition here is strong, but proof is missing.
• Fungal and bacterial growth, in lab tests only: In test tubes, cassia oil slows many bacteria and yeasts. That result is clear in the lab. Whether it clears any infection in a person is not established. Do not use it in place of treatment for an infection.

Which foods are rich in Cinnamomum cassia?

1. Ground cinnamon in most shops
2. Cinnamon sticks used in cooking
3. Chai and spiced teas
4. Mulled wine and cider
5. Chinese five-spice powder
6. Cinnamon buns, biscuits and cereals

Practical Tips:

Spice amounts in normal food are fine for most adults. The coumarin issue grows with daily heavy use, not with the odd sprinkle.

Children are the group to watch. Their small body weight makes the daily coumarin limit easy to pass. Cinnamon-heavy porridge or sweets every day is the sort of habit to think about.

Ceylon cinnamon is a different tree with far less coumarin. If you eat cinnamon daily, that is the safer kitchen choice.

What are the side effects of Cinnamomum cassia?

• Heartburn or stomach upset
• Mouth soreness or mouth ulcers, mostly from oils and strong sweets
• Skin rash or contact allergy
• Rise in liver blood tests
• Rare liver injury with high daily supplement use
• Low blood sugar when combined with diabetes drugs
• Burns from undiluted essential oil on skin or lips
• Allergic reaction, with swelling or wheeze

Good to know:

Most people who use cassia as a spice have no trouble at all. Problems cluster around two things: daily high-dose capsules, and the strong essential oil.

Liver injury is rare but real. It has been reported with cassia supplements and with heavy daily spice use. It usually settles after the product is stopped.

Mouth and skin reactions are the most common complaints. They are unpleasant but not dangerous for most people.

How much Cinnamomum cassia should you take?

• Recommended daily: Cassia is a food spice first. Normal cooking amounts are the usual intake for most people. Supplement labels often carry 500 mg to 1 g of bark powder per dose. Trials have tested roughly 1 g to 6 g a day. Those figures are background here, not advice for you. One ceiling matters. European food safety advice sets a daily coumarin limit of 0.1 mg per kg of body weight. A heaped teaspoon of cassia can reach or pass that limit for a child or a small adult.
• Best time of day: Timing has not been properly tested. People who take it for blood sugar usually take it with meals. As a cooking spice, time of day does not matter.
• With or without food: With food is the usual choice. Food may ease the heartburn some people get from it. Taking it with a meal also fits the idea of slowing the sugar rise after eating.
• Time to effect: If it does anything, expect weeks rather than days. Most trials measured change at 8 to 12 weeks. Many people see no measurable change at all. Where blood sugar effects were found, they were small.
• How long to take it: Most trials ran 6 to 16 weeks. Daily supplement use beyond that has not been well studied. Coumarin builds up with daily use, so long stretches raise the liver concern. Many labels suggest breaks between courses. Talk to your doctor before taking cassia capsules for months on end.