Research undermines the spicy claims
DOES TI WORK:Despite claims as to its efficacy, research shows cinnamon makes little difference to treatment of diabetes
CINNAMON WAS hailed for its medicinal value in ancient China, Egypt and Rome. Access to cinnamon was at the heart of Portuguese, Dutch and British claims to govern the island of Sri Lanka (formerly Ceylon). Then, as now, cinnamon was an important spice for flavouring foods and drinks.
In 2003, a research study was published which reported several benefits for type 2 diabetes patients who took 1g-6g of cinnamon daily. This report made cinnamon very popular as a dietary supplement. However, several varieties of cinnamon exist. For many years, most commercial cinnamon was grown in Ceylon and called "Ceylon cinnamon" or "true cinnamon".
Due in part to various wars in the region during the 20th century, cinnamon is now cultivated in many parts of the world. This has led to some variation within the species and identification of related species.
The study, published in 2003, used "Chinese cinnamon" or "cassia cinnamon". Although the two species are very similar, cassia cinnamon is less expensive than Ceylon cinnamon, as it has a harsher taste. Many products contain a mixture of the two types of cinnamon.
Evidence from studies
A number of laboratory experiments had found that various compounds in cinnamon affect glucose and insulin levels. Researchers from Pakistan tested the effect of cinnamon on patients with type 2 diabetes because of these findings, and this led to the 2003 publication of their research.
Their study divided patients into groups of 10 who each received 1g, 3g or 6g of cinnamon, or a placebo, daily. After 40 days, all those taking cinnamon had significant improvements in fasting blood sugar, triglyceride, LDL and total cholesterol levels. While all these changes are beneficial for diabetic patients, those taking the placebo had no changes.
Following on from this first study, four similar studies have been published. They all used cassia cinnamon, not Ceylon cinnamon. A German study found reductions in fasting blood sugar levels after diabetic patients took 1g cinnamon daily for four months.
However, none of the other blood tests done showed any improvements. Research conducted in the Netherlands, the United States and Thailand found no changes in any blood test conducted on the type 2 diabetes patients in these studies. Earlier this year, a systematic review of all these studies concluded that cinnamon does not appear to offer benefit to diabetic patients.
None of the clinical trials reported adverse effects with doses up to 6g per day, or taking the supplement for up to four months.
However, cassia cinnamon contains coumarin which is toxic to rat livers.
There are fears that very high doses might be toxic in humans, although this would require consuming huge amounts of cinnamon.
More realistically, people with liver problems might be more sensitive to coumarin and should be very careful taking cinnamon at the supplement doses. Also, some pharmaceutical drugs carry a risk of damaging the liver, and should not be taken together with cinnamon supplements. Anyone concerned about this should talk with their doctor or pharmacist.
Ceylon cinnamon contains barely any coumarin and thus does not raise this concern. However, none of the research with diabetic patients has used Ceylon cinnamon.
While cinnamon contains compounds that interact with insulin and blood sugar, crude cinnamon supplements do not show consistent benefits in diabetic patients.
Current research suggests that cinnamon is not an effective treatment for diabetes.
Patients with diabetes whose blood sugar levels are stable should talk to their doctor about any plans to try cinnamon or any other supplement.
If they have an effect, other medications may need to be adjusted.
• Dónal O'Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University. He authored Alternative Medicine: The Christian Handbook, Updated and Expanded Edition, Zondervan, 2007