Spice science: exploring cinnamon’s role in blood sugar control

Cinnamon is a spice that has been used around the world for thousands of years. In addition to its use as a culinary ingredient, cinnamon contains bioactive compounds that have attracted attention for their potential health effects. One of these effects is how it can influence blood sugar levels which could have relevance for people with diabetes. In this podcast episode, I’ll look at what the clinical trials have to say on how cinnamon may help people with diabetes to keep their blood sugar levels under better control.

Links referred to in the podcast

• Review of cinnamon supplementation on metabolic markers in people with T2DM https://academic.oup.com/nutritionreviews/article-abstract/83/2/249/7699031

Episode transcript
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Transcript

Cinnamon is a spice that has been used around the world for thousands of years. In addition to its use as a culinary ingredient, cinnamon contains bioactive compounds that have attracted attention for their potential health effects. One of these effects is how it can influence blood sugar levels which could have relevance for people with diabetes. In this podcast episode, I’ll look at what the clinical trials have to say on how cinnamon may help people with diabetes to keep their blood sugar levels under better control.

Cinnamon is a spice derived from the bark of several tree species within the genus Cinnamomum. Its historical use as an ingredient can be traced all the way back to Ancient Egypt. Previously, cinnamon was considered rare and valuable, but it is now widely available and commonly used in a variety of foods and recipes.

The characteristic aroma and flavour of cinnamon are attributed to its essential oil content, notably the compound cinnamaldehyde. Cinnamaldehyde has shown anti-inflammatory, antibacterial, antioxidant and anticancer activity in experimental settings. In terms of blood glucose regulation, cinnamaldehyde has demonstrated antihyperglycemic effects and it appears to do this by suppressing insulin resistance and increasing glucose uptake in muscle and fat cells, producing effects similar to insulin at least in preclinical studies.

Another fun fact about cinnamon is it has shown prebiotic effects, potentially supporting the growth of beneficial gut bacteria and limiting the proliferation of harmful bacteria.

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.

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. At least in animal and in vitro studies, polyphenols found in cinnamon have shown insulin-like effects and the ability to increase glucose uptake by muscle and fat cell. In human clinical trials, cinnamon supplementation has sometimes been associated with reductions in glucose, triglycerides, and cholesterol concentrations in people with type 2 diabetes. However, not all studies have reported positive findings, and many have involved small sample sizes.

Now this topic of the effect of cinnamon on blood sugar control was one I first covered in this podcast 5 years ago. And back then, based on the research to date, the field included 18 clinical trials involving 1,100 participants. Taken together, the results were supportive of cinnamon reducing fasting blood glucose in people with type 2 diabetes, although one of the key measures of long-term glycaemic control (called HbA1c) even though it went down, it was not quite considered statistically significant. At the time I said that with more trials this small effect may prove to be significant.

Well, it seems that comment has aged well. Because in only of June this year, an updated systematic review has been published again looking at the effects of cinnamon on metabolic biomarkers in people with type 2 diabetes. This time, a total of 28 randomised-controlled trials that ran for between 1 and 4 months involving over 3,000 participants could be analysed which is 10 more trials than when the last major review was done 6 years before. And I’ll link to this review in the show notes. https://academic.oup.com/nutritionreviews/article-abstract/83/2/249/7699031

So, what did they find? People taking cinnamon showed significantly lower fasting glucose, post-prandial glucose (which is glucose levels after a meal), HbA1c and insulin resistance compared to the placebo group. There was also evidence that cinnamon could reduce total cholesterol and triglycerides. And interestingly, while doses of cinnamon below 2 grams per day and above 2 grams per day showed benefits on blood glucose, it was only cinnamon taken at doses below 2 grams per day that could improve HbA1c and insulin resistance. This somewhat paradoxical finding has been seen in other reviews which endorses the ‘less in more’ approach for using cinnamon which is relevant if you take into account potential safety issues.

So, on that point, is cinnamon safe to consume as a higher dose supplement? Before I answer that, realise that there are two main types of cinnamon. The first is cassia cinnamon, also called ‘regular’ cinnamon and this is the most common type you’ll find in supermarkets. Then there is Ceylon cinnamon, also known as ‘true’ cinnamon, Ceylon cinnamon has a lighter and less bitter taste. 

There are some concerns regarding the safety of cinnamon in higher doses and side effects such as headaches and diarrhea have been reported. But human studies on the adverse effects of cinnamon supplementation are fairly limited. While Cassia cinnamon is safe to eat in the amounts commonly used as a spice or flavouring in food, 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. Ceylon cinnamon is likely a better supplemental option than cassia cinnamon, due to its lower coumarin content.

So, let’s wrap all this up. Despite promising results from laboratory and clinical studies, it’s important to recognise the limitations of existing research. The majority of human trials investigating cinnamon’s effects on blood glucose have been relatively short in duration, with considerable variation in dose, cinnamon type, and study design. For anyone with diabetes, the answer to the question of if cinnamon has a clinical role to play in managing blood sugars seems to be that it could offer a small benefit, but the magnitude of benefit should not mean that anyone taking medications will be switching to cinnamon any time soon. And because of some unanswered questions on the safety profile of cinnamon taken as a dedicated high dose supplement, rather than just a sprinkling in food or drink to spice it up, then it would be prudent for anyone not to trial such a supplement without talking first to their treating healthcare professional for their diabetes especially if taking diabetes medications or managing any liver problems.

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, or else head over to my webpage at 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