The grapefruit has a pleasant, tart flavor and comes with a long list of health benefits. It is a well-known fact that grapefruit juice consumption promotes liver health and enhances the fruit's antioxidant effects. Grapefruit also has a long-standing reputation of being good for cardiovascular health, and it is recommended as a part of the DASH diet, which stands for Dietary Approaches to Stop Hypertension. However, these benefits may come with a caveat. A recent study suggests that consumption of grapefruit juice may have an unexpected side effect for some people.
A QT interval is a measurement between Q and T waves in the heart's electrical cycle. Long QT syndrome (LQTS) is a disorder that suddenly alters the heart rhythm, causing episodes of potentially dangerous arrhythmia. A double-blind study, carried in Tel Aviv (Israel) by a scientific team of the Tel Aviv Sourasky Medical Center and the affiliated Sackler School of Medicine (New York), tested the effects of grapefruit juice on the QT interval with the methodology used by the pharmaceutical industry to test new drugs.
The trial involved 30 healthy adults and 10 patients with LQTS. Healthy adults were given either two liters of grapefruit juice to drink or 400 mg of oral moxifloxacin, an antibiotic observed to have mild QT interval prolongation effects. LQTS patients were given two liters of grapefruit juice. The effects were studied via electrocardiograms (ECGs).
The collected data showed that grapefruit juice consumption significantly prolongs QT interval, which was the most noticeable among the LQTS patients.
What is particularly interesting about these results is that female participants showed stronger responses to both grapefruit juice and moxifloxacin than men.
What Does this Mean?
Because of its ability to prolong QT interval, a large consumption of grapefruit for heart patients, especially those with LQTS, as well as those on antiarrhythmic medications is contraindicated in order to minimize the risk of arrhythmia and its potentially life-threatening consequences.
Since the study has focused on patients with heart rhythm disorders, these findings do not suggest restrictions for the healthy, general population.
- HearthRhythm, Grapefruit Juice prolongs the QT Interval of Healthy Volunteers and Patients with Long QT syndrome, 2019
- National Institutes of Health, National Lung, Heart and Blood Institute - Long QT Syndrome