19 February 2023 , 10:00
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Grapefruits are popular for their sweet taste and immune system benefits, but scientists have warned that the tangy fruit could be harmful if taken alongside a number of drugs.
Research has also suggested that grapefruit may interact dangerously with tonic water when consumed by certain people.
Experts have claimed that grapefruit inhibits the enzyme CYP3A4, which metabolises more than 65 percent of all drugs.
Science Direct explained: “A considerable number of drugs are affected, but the most important causes of concern are probably some of the statins, extensively prescribed as cholesterol reducers."
“Do not drink grapefruit juice if you're taking simvastatin,” says the NHS.
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“Grapefruit juice increases the level of simvastatin in your blood and makes side effects more likely.”
Previous research has shown that combining grapefruit with tonic water containing quinine - a naturally occurring substance - may spur similar effects.
“People who have a heart rhythm disorder should avoid taking grapefruit juice and tonic water together. That combination might worsen some heart conditions,” added Medline Plus.
“Also, don’t drink red wine and grapefruit juice together if you take any medications. This combination can make grapefruit juice interact with medications even more.”
The tonic and grapefruit combination is a health risk because the juice may inhibit enzymes responsible for the metabolism of quinine, writes Science Direct.
The use of grapefruit juice alongside quinine may increase concentrations of the nutrient in the blood, and increase the risk of quinine side effects.
A 2003 report, titled ‘Grapefruit and tonic: a deadly combination in a patient with the long QT syndrome’, warned about the combination risk.
A 31-year-old with long QT syndrome drank excessive amounts of tonic water containing quinine alongside grapefruit juice.
The patient was admitted to the hospital with torsade de pointes, a specific type of abnormal heart rhythm that can lead to sudden cardiac arrest.
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People who have a heart rhythm disorder should avoid taking grapefruit juice and tonic water together (Getty Images)Within two days of discontinuing the drink, the patient's heart rhythm stabilised.
The authors of the case suggested that the heart rhythm problems may have been triggered by the interaction of quinine with grapefruit juice.
What is Long QT Syndrome?
According to the Mayo Clinic, Long QT syndrome is defined as a heart signalling disorder that triggers rapid and chaotic heartbeats.
The condition is thought to be passed down by faulty genes inherited by parents, but the NHS states that certain medicines like antibiotics may trigger the condition too.
“Drug-induced long QT syndrome tends to only affect people who already have a tendency to develop the condition.” explains the NHS.
Because grapefruit juice can affect electrical currents in the heart, it may be prudent to avoid mixing the drink with certain supplements too.