Cinnamon is a spice that has been used around the world for thousands of years. It is far more than a food accompaniment. It’s the use of cinnamon as a medicinal agent that has scientists interested because of unique compounds found in cinnamon that appear to offer some unique health benefits. In today’s podcast, I’ll look at those health benefits with the spotlight firmly placed on how cinnamon may help people with diabetes keep their blood sugar levels under better control. 

Cinnamon is a spice obtained from the inner bark of several tree species from the genus Cinnamomum. It has been used as an ingredient throughout history, dating back as far as Ancient Egypt. It used to be rare and valuable and was regarded as a gift fit for kings. These days, cinnamon is cheap, available in every supermarket and found as an ingredient in various foods and recipes.

The distinct smell and flavour of cinnamon are due to the oily part, which is very high in the compound cinnamaldehyde. Scientists believe that this compound is responsible for most of cinnamon's powerful effects on health and metabolism. 

Cinnamon also contains large amounts of polyphenol antioxidants. Antioxidants can help protect the body from disease and are found in fruits, vegetables, herbs and spices. The antioxidants in cinnamon have been found to have anti-inflammatory effects. Some spices, including cinnamon, have prebiotic properties that promote the growth of beneficial bacteria and help suppress the growth of pathogenic bacteria. Therefore, including spices regularly in your diet may help improve gut health. Cinnamon is also a useful source of manganese and contains small amounts of calcium and fibre.

There are lots of health claims made about humble cinnamon but most of them such as anti-fungal, anti-HIV, anti-cancer, lowering blood pressure and preventing Alzheimer’s disease come mostly studies out of a lab in cells or animals so I won’t give them much attention today. When it comes to a decent volume of human clinical research, it is cinnamon’s potential role in regulating blood glucose that attracts the most attention.

Diabetes

Due to a growing worldwide prevalence of diabetes, researchers are interested in applications of natural foods like cinnamon to control blood sugar and curb inflammation. Compounds called polyphenols found in cinnamon show effects similar to insulin and can promote glucose use by muscle and adipose cells – at least in animal and cell culture studies so what do human clinical trials show?

Studies in humans have shown promising results for cinnamon lowering glucose, triglyceride and cholesterol levels in people with type 2 diabetes. Not all of the clinical trials though have shown positive results, and all suffered from issues of small numbers of people studied.

Way back in 2008, researchers first complied the human research that had been done so far into a meta-analysis. Just 5 studies that used a randomised controlled design of giving cinnamon or a placebo to people with type 2 diabetes could be identified. Collectively these involved a total of 282 people. 

The findings of the analysis were less than inspiring. The use of cinnamon at doses ranging from 1 to 6 grams per day for periods of up to 16 weeks showed no benefit in improving fasting blood glucose levels or overall glucose control. No improvements in total cholesterol, triglycerides or LDL or HDL cholesterol could be seen as well.

The authors of the meta-analysis acknowledged that the number of people in the studies may have been too small to detect a significant benefit for cinnamon.

But the research didn’t stop there and in 2012 an updated meta-analysis was published that included yet more studies. And I’ll link to this study in the show notes https://pubmed.ncbi.nlm.nih.gov/22579946

This time 6 trials could be analysed that were of sufficient research quality, and collectively involved a lot more people - 435 in total. Doses of cinnamon varied from 1 to 6 grams per day and treatment length ranged between 40 days and 4 months. 

Cinnamon did show a small benefit in improving measures of glycaemic control, but the magnitude of the effect was very small. The longer-term measure of glycaemic control of glycosylated haemoglobin (HbA1c) fell by a very small 0.09 percentage points which is not that clinically significant. Fasting glucose fell by an average of 0.84 mmol/L which appears large, although this fall wasn’t statistically significant.

The authors of the meta-analysis acknowledged that the number of clinical trials performed so far is small as too the number of people who have taken part in them.

So, since 2012, with more clinical trials published, a more recent 2013 review is painting a more positive picture even though just one year has elapsed since the last meta-analysis. A total of 10 studies of sufficient research quality were included in the new review which I’ll link to in the show notes https://pubmed.ncbi.nlm.nih.gov/24019277

Collectively, these trials involved a total of 543 people. Doses of cinnamon varied from 120 milligrams to 6 grams per day and treatment length ranged between 4 to 18 weeks. The clinical outcomes from the review were small in magnitude but were statistically significant. A decrease in fasting glucose, total cholesterol, LDL cholesterol and triglycerides, with a rise in HDL cholesterol all pointed to a favourable benefit. The downside of the review was that the variability in the clinical outcomes between studies was high. Differences in dosage and timing of cinnamon likely explain much of the variability, which makes it hard to translate the results into patient recommendations just yet.

And now to finally complete the picture and to illustrate how science advances one study at a time, a meta-analysis published only last year in 2019 could include 18 clinical trials and 1100 participants and I’ll link to the study in the show notes https://pubmed.ncbi.nlm.nih.gov/30935562 And what they found was supportive of cinnamon reducing fasting blood glucose in people with T2DM. And even though HbA1c reduced by 0.24 percentage points, this was not statistically significant, but at least was in the right direction. And dare I say, with more trials this small effect may prove to be significant.

So, what to make of all this? For anyone with diabetes, the question of if cinnamon has a clinical role to play in managing diabetes is still not clearly answered, but the signs are positive, but the magnitude of benefit should not mean that anyone taking medications will be switching to cinnamon any time soon. Until the questions of dosage and duration are more clearly answered, cinnamon cannot replace lifestyle changes and prescription medications just yet.

Bodyweight

But if cinnamon does have a role to play in controlling blood sugar, could this perhaps translate into a favourable effect on body weight? Outside of diabetes, there is interest in seeing if cinnamon could also help with obesity. Clinical trials using cinnamon in obesity and weight loss though have mostly been small in number and haven’t always shown a positive benefit. With new clinical trials recently published, a recent review is painting a more positive picture.

For the review, Iranian researchers compiled the results from 12 randomised controlled clinical trials involving 783 people that investigated the effects of cinnamon on obesity measures. And I’ll link to the study in the show notes https://pubmed.ncbi.nlm.nih.gov/30799194                                   

The pooled results found that cinnamon significantly decreased body weight by 1 kilogram. Waist circumference showed a favourable decline with a fall of just over 2 centimetres. Body fat also fell by 1 percent. Digging deeper, the best results seemed to be with those under 50 years of age. As for dosage, 2 grams of cinnamon per day for greater than 12 weeks was the most effective.

The results from this review did find that cinnamon is effective in making very small inroads into body fat. But the loss of 1 kilogram of body weight after several months is hardly spectacular so it is unlikely that it would be recommended as a first-line therapy for obesity.

Safety

There  are two main types of cinnamon. The first is cassia cinnamon,  also called “regular” cinnamon, this is the most commonly used type. Then there is Ceylon cinnamon, also known as “true” cinnamon, Ceylon has a lighter and less bitter taste.

Cassia cinnamon is more commonly found in supermarkets, given that it’s much cheaper than Ceylon cinnamon. While Cassia cinnamon is safe to eat in small to moderate amounts, eating too much may cause health problems because it contains high amounts of a compound called coumarin which can cause liver damage, breathing problems and interfere with some medications when ingested in high doses. The standard dose for anti-diabetic purposes is 1-6g of cinnamon daily, taken with carbohydrate-containing meals. Ceylon cinnamon is always a better supplemental option than cassia cinnamon, due to the lower coumarin content. 

So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.

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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.