Cinnamon may interfere with the effect of medications, according to new study

Although cinnamon is a spice added to many foods, it has a long history of use in traditional medicine in many cultures.

Today, cinnamon products are sold as dietary supplements to help with a variety of health conditions, including treating diabetes, promoting weight loss , and relieving allergic rhinitis and other inflammatory conditions. But how much cinnamon is too much? Could there be negative impacts from consuming too much cinnamon products?

People should be cautious because cinnamon may affect the effect of medications , according to a study published in the journal Food Chemistry: Molecular Sciences. The authors warned against overconsumption of cinnamon-containing substances, especially in individuals with other health conditions.

To help us understand the study results and what the key takeaways are about cinnamon consumption, CNN spoke with Dr. Leana Wen, an emergency physician and adjunct associate professor at George Washington University.

CNN: What is cinnamon — where does it come from and what are its potentially beneficial health effects?

Dr. Leana Wen: Cinnamon is a spice that comes from the dried bark of Cinnamomum trees. Ceylon cinnamon, sometimes called “true” cinnamon, comes from Cinnamomum verum trees. While some studies have suggested that cinnamon supplementation may be helpful in treating diabetes or aiding in weight loss, more research is needed to investigate the benefits . Similarly, while preliminary research suggests that Ceylon cinnamon nasal spray may have a role in helping with allergic rhinitis, more research is needed to confirm that it can be a treatment.

The National Center for Complementary and Integrative Health states that “research does not clearly support the use of cinnamon for any health condition.” Cinnamon is not approved by the U.S. Food and Drug Administration (FDA) for the treatment of any medical condition, for example.

CNN: What is known about the possible risks of consuming cinnamon?

Wen: Cassia cinnamon may contain high levels of coumarin, a blood thinner. Ceylon cinnamon may also contain trace amounts of coumarin. If someone who is already taking blood thinners ingests a large amount of coumarin, it may increase the risk of bleeding. In addition, there are known interactions between coumarin and the liver. Long-term use of cinnamon products high in coumarin may pose health risks to people with liver disease. In addition, the National Center for Complementary and Integrative Health states that there are “theoretical reasons” to believe that there may be interactions between cinnamon and anticancer medications and nicotine.

CNN: What did this new study look at?

Wen: This new study examined the main active ingredient in cinnamon, called cinnamaldehyde. The researchers first looked at whether cinnamaldehyde is well absorbed when ingested orally by examining gastric and intestinal fluids. They found that it is 100% bioaccessible in both fasted and fed fluids. This means that regardless of whether someone is fasting or has just eaten, cinnamaldehyde is expected to be well absorbed. They then found that cinnamaldehyde is rapidly metabolized to another compound, cinnamic acid, and that it can activate multiple receptors that affect drug metabolism. The potential interference with drug metabolism is what led the authors to conclude that excessive consumption may induce herb-drug interactions. They recommend further research to investigate these potential interactions. Until such studies are completed, as the researchers noted in an associated press release, they recommend that people considering taking cinnamon as a dietary supplement exercise caution and consult a physician before use.

CNN: Who should be cautious?

Wen: According to the study researchers, the list of chronic conditions that should warrant caution before trying cinnamon supplementation includes hypertension, diabetes, cancer, arthritis, asthma, obesity, HIV/AIDS, and depression. I would add to this list anyone taking blood thinning medications—for example, someone with a history of heart disease and stroke, any medications that are eliminated by the liver, and other dietary supplements that may interact with cinnamon, including turmeric, ginseng, and ginkgo biloba.

CNN: What about sprinkling cinnamon in coffee or on pancakes? Should we be concerned?

Wen : The researchers are quite clear that sprinkling cinnamon for typical culinary use is unlikely to cause problems. What they do warn about is what they call “excessive consumption.” This is not clearly defined, as the study was not designed to examine what might be considered too high a level of cinnamon. What excessive consumption likely refers to is the use of concentrated cinnamon products, such as cinnamon supplements, over a prolonged period of time—for example, taking cinnamon capsules every day for months. Individuals considering taking cinnamon supplements should check with their doctors to check for possible drug interactions. They should also be aware that there is no clear evidence for the benefit of cinnamon supplementation.

CNN: What else do you wish people knew before they started taking dietary supplements?

Wen: People should be cautious when taking dietary supplements. Just because something is marketed as “natural” doesn’t mean it’s safe. Also, something that is safe in small amounts can be dangerous in large amounts. People should always tell their doctor about any supplements they are taking or considering taking to assess drug interactions.