Eating grapefruit could trigger deadly organ failure for the millions of Brits taking common medications to treat a host of conditions like high cholesterol and an irregular heartbeat, a medic has warned.
BBC Morning Live regular Dr Xand van Tulleken said people taking certain drugs should be cautious about eating the fruit, as well as its juice or jam, as it could interefere with medication for days after consumption.
‘If you’re eating grapefruit and you take drugs regularly, you should definitely have an alertness and a knowledge of what’s going on because grapefruit can be dangerous,’ he said in a recent television appearence.
This is because an organic compound in the fruit deactivates an enzyme in the intestines that breaks down the medication.
Dr Van Tulleken said this could have serious consequences, leading to a potentially dangerous build-up of the drug in the body.
‘When we take medication our bodies break them down so we can excrete them harmlessly after they’ve worked – so grapefruit can either stop breaking down the drugs so you got a very high dose and that can have quite toxic effects,’ he said.
He listed the cholesterol medication statins, blood pressure medication, psychiatric medication, immunosuppressants like those used by organ donation patients and drugs that regulate a fast heart, called antiarrhythmics, as just some examples.
‘Half a glass [of grapefruit juice] can be enough to alter the way you process that drug for many days,’ he added.
BBC Morning Live regular Dr Xand van Tulleken said people taking certain drugs needed to be cautious about eating grapefruit as well as it’s juice or jam
‘I’d say if you’re on a regular medication check with your pharmacist check with your GP before you eat a grapefruit.’
Grapefruit contains compounds called furanocoumarins which can interfere with an enzyme in the small intestine, called CYP3A4.
This enzyme is responsible for breaking down nearly half of all medicines, enabling them to be absorbed by the body correctly.
The extent to which furanocoumarins impacts medication varies depending on the amount of CYP3A4 someone produces, the exact drug taken, and the precise amount of grapefruit a patient eats or drink.
With statins for example, grapefruit can lead to too much of the drug being released into the bloodstream and taking longer for the body to break down, resulting in a more potent dose, and increasing the risk of side effects.
On the milder side, this can lead an increased risk of headaches, dizziness, muscle pain and fatigue.
But in more extreme cases it can lead to liver, muscle damage and kidney failure.
Studies suggest it doesn’t take much grapefruit to have a potent impact on how the body processes medication.
Grapefruit contains compounds called furanocoumarins which interfere with an enzyme in the small intestine that breaks down medications for the body to absorb
Just a single glass of juice can reduce the production of CYP3A4 by up to 47 per cent.
Furanocoumarins can also stay in the body and inhibit the enzyme for up to 24 hours after a person consumes grapefruit.
And it’s not just grapefruit. Some closely-related fruits also have a similar affect.
These include Seville oranges, often used to make orange marmalade, pomelos, and tangelos which are a cross between tangerines and grapefruit.
Dr Van Tulleken also warned about the impact that foods rich in vitamin K, found in vegetables like broccoli and spinach, can have on the commonly prescribed blood thinner warfarin.
Vitamin K helps blood clot so can counteract warfarin, which is prescribed to prevent these clots and reduce the risk of deadly heart attacks and strokes.
Dr Van Tulleken said patients on warfarin should manage their intake of vitamin K rich foods, and eat a little bit throughout the week rather than a massive intake on a single day.
However, he added ‘consistency’ in vitamin K intake was key, advice echoed by the NHS.
Mixing food, drink and some herbal remedies with medications can cause an array of side effects
The health service doesn’t advise a specific safe intake of vitamin K for patients taking warfarin.
Instead, it emphasises that patients should keep their diet stable as their warfarin prescription will be matched to compensate for their vitamin K intake and ensure the drug still works.
Patients on warfarin wanting to significantly change their diet, for example to lose weight, should speak to their medical team before doing so.
They are still advised to eat vitamin K foods, rather than avoid them completely, as it helps in vital bodily functions like helping wounds heal.
Other foods rich in vitamin K include chickpeas, liver, egg yolks, some cheeses, avocados and olive oil.
[Notigroup Newsroom in collaboration with other media outlets, with information from the following sources]
