Taking tablets with popular breakfast fruit could be ‘dangerous’ and risk organ failure, top doctor warns

Eating grapefruit could trigger deadly organ failure for the millions of Brits taking common medications to treat a host of conditions such as 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 interfere 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 appearance.

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 stop breaking down the drugs so you [get] a very high dose and that can have quite toxic effects,’ he said. 

He listed the cholesterol medication statins; blood pressure drugs; psychiatric medication; immunosuppressants, like those used by organ donation patients; and drugs that regulate an irregular or fast heartbeat, 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. 

‘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 impact 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, resulting in a more potent dose and increasing the risk of side effects. 

On the milder side, these can include headaches, dizziness, muscle pain and fatigue. 

But in more extreme cases it can lead to liver and muscle damage and kidney failure.

Studies suggest it doesn’t take much grapefruit to have a potent impact on how the body processes medication. 

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 effect.  

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. 

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.