Although grapefruit is usually good for you, it can be bad for you if you take a calcium-channel blocker for high blood pressure. Grapefruit juice can interact with some blood pressure medications, causing adverse effects that can even be life-threatening. Not all drugs pose this problem, but to be on the safe side, talk with your doctor about your diet restrictions if you're on a blood pressure medication.
Grapefruit and Drug Metabolism
Grapefruit inhibits the effectiveness of your CYP34A enzyme. If your CYP34A enzyme isn't working properly, some medications will stay in your bloodstream longer than they should. The medication may build up in your system, essentially creating an overdose. Not all drugs interact with grapefruit juice -- or grapefruit in any form. But calcium-channel blockers, a type of blood pressure medication, are dependent on your CYP34A enzyme. If you combine grapefruit and calcium-channel blockers, the medication may elevate to dangerous levels in your bloodstream. If this happens, your blood pressure may drop more than it should. In severe cases, your heart could stop.
Calcium Channel Blockers
Two calcium-channel blockers -- felodipine and nidefipine -- are greatly affected by grapefruit juice. Three other calcium-channel blockers -- verapamil, diltiazem and amlodipine -- are modestly affected by the metabolism-blocking properties in grapefruit, according to the Harvard Medical School Family Health Guide. If grapefruit affects a blood pressure medication you take, a single glass of juice could lower metabolism of the drug by 47 percent, according to the Harvard guide.
Statins
High cholesterol levels clog your arteries, making it difficult for for blood to travel freely to your heart and other vital organs. If elevated cholesterol contributes to your high blood pressure, your doctor may prescribe a statin. If you take a statin, do not combine it with grapefruit juice. Drinking grapefruit juice while taking a statin increases your risk of side effects including liver damage, severe muscle pain and muscle damage. Statin-induced muscle damage sometimes leads to kidney failure.
Grapefruit Juice and Triglycerides
High blood pressure damages your arteries, making it easier for low-density lipoprotein cholesterol and triglycerides to accumulate in them. This may, in turn, further elevate your blood pressure. Adding grapefruit or grapefruit juice to your diet could lower your triglycerides, according to a study led by Shela Gorinstein, a researcher at Hebrew University of Jerusalem. The 57 participants in Gorenstein's study added either white or red grapefruit to their diets for four weeks. At the end of the trial, all participants tested lower for triglycerides. Red grapefruit worked better than white, according to the study, published in the March 2006 issue of the “Journal of Agricultural and Food Chemistry.” You may want to consider eating more grapefruit or drinking more grapefruit juice if you're concerned about your triglycerides and you aren't taking any medications that interact with this fruit.
References
- The Harvard Medical School Family Health Guide: Grapefruit and Medication: A Cautionary Note; Feb. 2006
- “The New York Times”; Experts Reveal the Secret Powers of Grapefruit Juice; Nicholas Bakalar; March 21 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; Dec 16 2010
- American Heart Association: About High Blood Pressure
- University of Maryland Medical Center: Drug Treatments – Statins; Oct. 31 2006
