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What if the spice in your favorite dessert could do more than add flavor?

Coumarins, the natural compounds that give cinnamon its sweet, warm aroma, are also found in citrus peel, chamomile, parsley, and cherries. For centuries they have been used in herbal medicine and perfumes. Today, researchers are learning more about their potential health effects, including a role in regulating the growth of new blood vessels, a process known as angiogenesis.

This week, we’re exploring how coumarins connect everyday foods to cutting-edge cancer research, highlighting their unique chemistry, dietary sources, and emerging evidence of anti-angiogenic effects.

What Exactly are Coumarins?

Coumarins are natural plant compounds best known for giving cinnamon its sweet, hay-like aroma. Chemically, they belong to a group called benzopyrones—a structure made of a benzene ring fused to a lactone ring. Small changes to this structure create many different coumarin types, more than 1,800 of which have been identified in nature.

In plants, coumarins act as protectors, helping ward off pests and infections while also playing a role in growth and photosynthesis. In the human diet, they are found in foods such as cinnamon, citrus peel, chamomile tea, parsley, celery, and even some honeys and wines.

The richest food source is cinnamon. Cassia cinnamon, the type most commonly sold in supermarkets, contains much higher levels of coumarin than Ceylon cinnamon, often called “true cinnamon.” While coumarins from foods are generally safe at the levels we consume, very high intakes of cassia cinnamon may stress the liver in sensitive individuals. This is why European regulations set limits on coumarin content in certain cinnamon-flavored products.

What the Research Shows

A 2019 review published in Molecules examined how coumarins and their derivatives affect angiogenesis—the growth of new blood vessels that cancer cells often rely on to survive and spread.

Here’s what researchers found:

• Blocks growth signals: In cell studies, coumarins interfere with VEGF and FGF, two major pathways that drive new vessel formation.

• Slows endothelial cells: In lab and animal studies, coumarins reduce the ability of endothelial cells (which line blood vessels) to multiply, migrate, and form new capillaries.

• Eases stress and inflammation: Experimental models show coumarins lower oxidative stress and calm inflammatory pathways linked to cancer progression.

• Triggers cancer cell death: Certain coumarins prompt cancer cell lines to undergo programmed cell death while sparing healthy cells.

Taken together, these findings suggest that coumarins may target several hallmarks of cancer, including uncontrolled angiogenesis. While most of the evidence so far comes from laboratory and early experimental studies, it highlights the potential of coumarins as natural compounds that could support cancer prevention and treatment in the future.

Enjoy Coumarins in Everyday Foods

Coumarins are most abundant in cinnamon and citrus peel, but they also appear in many herbs and teas. Adding these foods to your routine can provide coumarins along with other health-supporting plant compounds.

Cassia cinnamon (the common supermarket variety): The richest source of coumarins. Best used occasionally—European guidelines recommend keeping intake below about 0.1 mg of coumarin per kg of body weight per day (≈ 1 teaspoon of Cassia for most adults) to avoid liver toxicity.

Ceylon cinnamon (“true” cinnamon): Contains only trace amounts of coumarin, making it the safer choice for frequent use, though it contributes little to total coumarin intake.

Citrus zest: Lemon, orange, and grapefruit peels are natural sources. Grating a little zest into tea, yogurt, or baked goods is an easy way to add coumarins.

Chamomile tea: Known for its calming effects, it also contains coumarins such as herniarin and umbelliferone.

Parsley and celery: Fresh herbs and vegetables that bring both flavor and a gentle coumarin boost.

Honey and propolis: Bees collect coumarins from plants, carrying them into these natural products.

There is no official daily target for coumarins, but enjoying a variety of herbs, teas, and citrus—as part of a balanced diet—can naturally introduce them into your meals. Choosing Ceylon cinnamon instead of Cassia is a simple way to limit excess intake while still enjoying the flavor.

Want to enjoy coumarin-rich foods as part of your daily routine?

Download our free Bioactive Spotlight guide featuring cinnamon, citrus, and chamomile—plus simple tips to help you safely add these plant compounds to your meals.

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_{*These statements have not been evaluated by the Food and Drug Administration.}

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- The Angiogenesis Foundation

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