David L. Katz, MD
Q. A friend told me I should avoid grapefruit because I'm on blood pressure medication. Why? And if that's true, should I be worried about all citrus?

— Carol Weirmier, Delhi, Ontario

A. Depending on what medication you're taking, grapefruit can cause your body to absorb that drug much faster. Grapefruit—along with Seville (sour) oranges—contains a family of compounds called furanocoumarins that experts believe interfere with certain metabolic enzymes. When furanocoumarins latch onto the enzymes, drugs are able to flood the bloodstream, dangerously increasing the dosage.

Among the drugs affected are some of the popular blood pressure–lowering agents known as calcium channel blockers. You have plenty of other options, so if you like grapefruit, talk to your doctor about switching medications. (Other citrus isn't a concern.)

Statins, tranquilizers, and antidepressants may also be metabolized faster due to furanocoumarins. Visit secure.pharmacytimes.com/lessons/200303-02.asp for a complete list of medications. For guidance about a variety of potential food and drug interactions, try this guide from M.D. Anderson Cancer Center: mdanderson.org/departments/nutrition/ (click on Food-Drug Interactions).
As a reminder, always consult your doctor for medical advice and treatment before starting any program.


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