Cinnamon is one of the world’s oldest and most widely used spices, valued not only for its flavor but also for its medicinal properties. Scientists from the U.S. National Center for Natural Products Research have discovered that an active ingredient in cinnamon can interfere with the effectiveness of prescription drugs. Their findings were published in the medical journal Food Chemistry.
Researchers have found that the main compound in cinnamon, cinnamaldehyde, activates receptors responsible for drug metabolism in the body. This means that consuming too much cinnamon could cause drugs to be excreted from the body faster than necessary, reducing their effectiveness.
“If a person takes large amounts of cinnamon supplements without informing their doctor, it could cause their medication to not work as intended,” said Shabana Khan, a senior researcher at the center.
While adding a little cinnamon to your morning coffee is harmless, high-concentration supplements can pose risks, especially for people with chronic conditions such as diabetes, hypertension, or depression.
Different types of cinnamon carry different levels of risk. Cinnamon oil, which is used externally as an antiseptic or seasoning, has virtually no effect on medications. However, cinnamon bark—especially the cassia variety, which contains high levels of coumarin, a natural anticoagulant—can be dangerous for people taking blood-thinning medications.
“True Ceylon cinnamon from Sri Lanka contains much less coumarin and is therefore considered safer,” said Amar Chittiboina, deputy director of the center.
Scientists note that it is important to continue studying the biochemical effects of cinnamon on the body and its potential interactions with drugs. However, until the results of clinical trials are available, the researchers advise caution.
“Anyone considering using cinnamon as a supplement—especially those taking prescription medications—should consult their doctor first,” said study co-author Bill Gurley.
