Not Always Better Together: Herbs, Spices and Medication Interactions

A teaspoon here, a dash there… For people who regularly take medications, could drugs interact with the spices and herbs used in recipes?

After all, it can happen with food. If an individual takes certain statin drugs to lower blood cholesterol levels and also drinks a lot of grapefruit juice, too much of the statin may stay in his or her body, increasing the risk of liver damage and kidney failure. On the flip side, grapefruit and other juices have been shown to decrease the effectiveness of some medication in treating allergy symptoms.

Ginger is thought to quell nausea and upset stomach, while garlic is often used to help prevent heart disease and cancer. But research shows that both may slow blood clotting in combination with anticoagulant drugs, so caution is warranted when eating ginger or garlic, or taking supplements containing them.

However, little research has been published on the potential for drug interactions when herbs and spices are used for culinary purposes instead of supplements. "It's likely a different story when spices and herbs are used in cooking and baking since the amount is smaller, compared to their use as a supplement," says Forrest Batz, PharmD, associate professor in the department of pharmacy practice at the University of Hawaii at Hilo. "Interactions may exist, but the bigger question is whether or not those interactions are clinically relevant. And so far, that doesn't seem to be the case."

Roy Upton, RH, DAyu, executive director of American Herbal Pharmacopoeia and expert advisory board member to the American Herbal Products Association's Botanical Safety Handbook, says that while there is research on specific compounds in spices and herbs, studies use concentrated preparations of the compounds, not the spice or herb in culinary amounts. For example, piperine, an alkaloid found in black pepper, has been shown to increase the bioavailability of several drugs, but Upton says no interactions have been noted with use of pepper as a spice. Scientific reviews of other spices — including anise, fennel, cayenne, parsley and several Indian spices — also show no reports of clinically relevant interactions.

Dean Elbe, PharmD, BCPP, co-author of the handbook Food Medication Interactions and a clinical pharmacy specialist at British Columbia Children's Hospital in Canada, agrees — adding that research in food and medication reactions is complicated in general. "There are many other variables that need to be considered aside from the amount of an herb or spice," Elbe says. "The specific varietal of the herb or spice, its potency, how much might be contributed throughout the day through different foods, even the specific genetics of an individual dictate how a person metabolizes medications and might affect the interaction between the herb or spice and drug."

To paraphrase the 16th-century physician Paracelsus, it may be a case of "the dose makes the poison." Mixing a few teaspoons of cinnamon into a recipe for two dozen cookies or stirring chopped garlic into pasta sauce is not a likely cause for concern over drug interactions. However, before taking a dietary supplement, as more than two-thirds of U.S. adults do, speaking with a pharmacist or a registered dietitian nutritionist about potential interactions is recommended.

Kerry Neville
Kerry Neville, MS, RD, helps commodity boards and better-for-you food companies translate the science of nutrition into the good food that people eat.