Food-Drug Interactions and CYP Enzyme Activity

Introduction to CYP2C9 Inhibitors and Inducers

Turmeric/Curcumin, garlic, ginger, and cranberry products can inhibit CYP2C9 activity, potentially increasing the risk of adverse effects with medications like warfarin, in patients consuming these products 1
St. John's Wort induces CYP2C9, potentially reducing the effectiveness of medications metabolized by this pathway, such as warfarin, in patients taking St. John's Wort supplements 1, 2

Many NSAIDs (e.g., diclofenac and naproxen) and sulfonylureas (e.g., glipizide) are metabolized by CYP2C9, and their effectiveness may be impacted by CYP2C9 inhibitors or inducers, according to the American Heart Association and the American Diabetes Association 2, 3

More frequent INR monitoring is recommended when starting, changing, or stopping foods known to affect CYP2C9, as suggested by the American College of Cardiology 2
Patients should maintain consistent dietary habits and inform healthcare providers about all dietary supplements and significant dietary changes, according to the National Institutes of Health guidelines and the American Medical Association 1
Particular caution is needed with dietary supplements containing concentrated forms of CYP2C9 inhibitors, which can increase the risk of adverse effects in patients taking warfarin or other CYP2C9 substrates, as warned by the FDA 1

Avoid sudden large changes in consumption of foods known to affect CYP2C9, and be especially vigilant with foods containing turmeric, garlic, ginger, and cranberry products if taking warfarin or other CYP2C9 substrates, as recommended by the Academy of Nutrition and Dietetics and the American Medical Association 1
Understand that consistent moderate intake is generally safer than sporadic high intake of these foods, and patients should consult with their healthcare providers before making any significant changes to their diet or supplement routine 1
Other substances, such as vegetables (e.g., celery, thyme, green pepper, carrots, and parsley) and cannabis products, can also affect drug metabolism through various mechanisms, as noted by the American Heart Association, the American College of Clinical Pharmacology, and the National Cancer Institute 4, 5, 6

The National Institute of Mental Health suggests that vegetables affecting CYP2D6 and CYP2C19 could theoretically alter SSRI metabolism, although the strength of evidence is limited 7
The American Medical Association advises considering potential interactions when patients report unusual drug responses, and maintaining consistent dietary habits for patients taking medications with narrow therapeutic indices 4