On The Shelf
Corey Diamond, PharmD
In addition to being one of the world’s most popular flavorings, cinnamon has been used for millennia as a naturopathic remedy. Cinnamon can be derived from the bark of several species of trees, all with varying pharmacokinetic profiles. However, the most common form sold in North America is known as cassia cinnamon, or Cinnamomum aromaticum.
Historically, cinnamon has had, with varying degrees of evidence, a plethora of therapeutic uses as a supplement, including as a weight loss agent, an antiemetic, a prevention for the common cold, and even a topical mosquito repellant. But today, it is used most commonly for its potential role in preventing and treating type 2 diabetes.
Type 2 diabetes: Is there a benefit?
The scientific consensus on the benefits of cinnamon for the treatment of type 2 diabetes is still unclear. The literature is conflicting, with roughly half of trials demonstrating significant benefit. Most of these trials have small sample sizes and high degrees of heterogeneity between outcomes.
The strongest evidence to date comes from a meta-analysis conducted by Allen and colleagues in 2013, published in the Annals of Family Medicine. The meta-analysis showed that 120 mg to 6 g of cassia cinnamon daily significantly reduced the mean fasting blood glucose of the study participants by 25 mg/dL within a 4- to 18-week period. However, there was no significant reduction in hemoglobin A1C (HBA1C), likely because many of the trials lasted fewer than 12 weeks. If cinnamon does have a benefit for patients with type 2 diabetes, the magnitude of the effect is likely small.
Cinnamon for prediabetes
While cinnamon’s benefit for type 2 diabetes appears to be marginal, the jury is still out on its role in prediabetes.
The evidence of cinnamon’s efficacy in patients with prediabetes is less robust than what is found in patients with type 2 diabetes. To date, there have only been a few clinical trials investigating cinnamon’s effects on patients with prediabetes, all of which are limited by a small sample size.
The most recent and now largest of these clinical trials in favor of cinnamon’s efficacy comes from a study by Romeo and colleagues, published in July in the Journal of the Endocrine Society. The researchers randomly assigned 54 individuals with impaired glucose tolerance or impaired fasting glucose to receive placebo or 500 mg of cinnamon capsules three times daily for 3 months. The capsules contained 300 mg of unspecified “Cinnamomum spp.” and 200 mg of C. burmannii. It is unknown if any patient received cassia cinnamon.
While the cinnamon group showed a significant improvement in fasting plasma glucose levels at week 12 compared with placebo—an average difference of 5 mg/dL between the groups, in favor of cinnamon—the results stemmed from a progressive increase in fasting plasma glucose in the placebo arm while that of the cinnamon arm remained unchanged from baseline. HBA1C also dropped, showing a 0.2% decrease between groups in favor of cinnamon, but again, the effect here is small.
This study indicates that while cinnamon may not be particularly potent in lowering prediabetic treatment metrics, it may help prevent a progressive uptick in them. Although this study is arguably the strongest in the current literature, it lacks long-term follow-up data on conversion rates. The authors wrote that further investigation is needed on “the impact of cinnamon on incident [type 2 diabetes] and/or remission of prediabetes.”
Are there any safety concerns?
The good news is that cinnamon has a great safety profile. Patients can safely take up to 6 g daily.
According to previous research, cassia cinnamon does contain trace amounts of coumarin, which may cause concerns for hepatotoxicity. But evidence suggests cassia cinnamon contains extremely small levels of coumarin, which would likely not cause liver damage.
Cinnamon is very well tolerated, and most patients report no significant adverse events. Rarely, cinnamon may cause a rash or allergic reaction. While the risks are quite low, patients with diabetes who are taking other antidiabetic agents may develop hypoglycemia due to cinnamon’s additive effects.
What to tell your patients
Ensure that patients understand there are several different varieties and species of cinnamon. If patients wish to add it to their medication regimen, they should look for cassia cinnamon specifically, as this is the species most studied.
Patients should understand that any beneficial effect of cinnamon is marginal. Cinnamon alone should never replace conventional therapy for diabetes.
Individuals can take up to 6 g daily of cassia cinnamon with little to no side effects. Ingesting large amounts of cinnamon may cause liver damage, so patients with preexisting liver disease or those taking hepatotoxic medications should use it with caution. Advise patients to monitor their blood sugar carefully, especially when initiating therapy.