Grapefruit juice can be harmful if you're taking blood pressure-lowering medicine. If you combine grapefruit juice with some types of blood pressure medication, your blood pressure could drop to dangerously low levels. Grapefruit does not affect all blood pressure medications equally, so talk to your doctor about possible interactions with the one you take.
Grapefruit and Drug Metabolizing
Grapefruit prevents your body's CYP34A enzyme from properly metabolizing some blood pressure medications. Drinking a single glass of grapefruit juice can decrease the rate of drug metabolism by 47 percent, according to the Harvard Medical School Family Health Guide. If medicine prescribed to lower your blood pressure isn't properly metabolized, an excess gets into your bloodstream, elevating its effectiveness. This could cause your blood pressure to become much lower than intended. In severe cases, your heart stops beating.
Calcium Channel Blockers
Do not drink grapefruit juice if you take a class of blood pressure medications called channel blockers. Examples include nifedipine and felodipine. Calcium channel blockers lower your blood pressure by blocking calcium from entering your blood vessels and heart. Calcium channel blockers are designed to be metabolized by the CYP34A enzyme. Since grapefruit juice prohibits this process, calcium channel blockers can become too concentrated in the bloodstream, greatly increasing your risk of side effects. If you use other types of blood pressure medications, ask your doctor if you can safely take grapefruit juice with them. Not all medications depend heavily on your CYP34A for metabolism.
Statins
Excess fat and cholesterol in your arteries make it difficult for your blood to flow properly, which may elevate your blood pressure. If you take statins to treat high cholesterol, avoid grapefruit and grapefruit juice. Statins, like calcium channel blockers, stay in your body longer than intended if combined with grapefruit juice. You increase your risk of side effects, including liver damage, muscle pain and muscle damage. Though uncommon, muscle damage from taking statins could lead to kidney failure.
Grapefruit to Lower Blood Pressure
If you aren't taking blood pressure drugs, grapefruit juice may prove helpful -- rather than harmful -- to your heart's health. Shela Gorinstein, a researcher at Hebrew University of Jerusalem, found a positive link between grapefruit consumption and lower triglycerides, a type of artery-clogging fat. She added grapefruit to the diets of 57 people for one month. All participants tested lower for triglycerides at the end of the study, according to the report in the "Journal of Agricultural and Food Chemistry" in March 2006. Red grapefruit proved more helpful than white.
References
- The Harvard Medical School Family Health Guide: Grapefruit and Medication: A Cautionary Note; February 2006
- The New York Times; Experts Reveal the Secret Powers of Grapefruit Juice; Nicholas Bakalar; March 2006
- "Journal of Agricultural and Food Chemistry"; Red Grapefruit Positively Influences Serium Triglyceride Level in Patients Suffering From Coronary Atherosclerosis: Studies in Vitro and in Humans; Shela Gorinstein, et al.; March 2006
- MayoClinic.com: Calcium Channel Blockers; December 2010
- American Heart Association: About High Blood Pressure
- University of Maryland Medical Center: Drug Treatments -- Statins; October 2006
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