Hundreds of people only just realising they can’t eat grapefruit after seeing viral meme

Many of us have a list of foods that don’t agree with us for whatever reason, whether it’s red wine giving you a bad headache or lactose playing havoc with your acid reflux.

But the reason why some people shouldn’t eat grapefruit isn’t one that appears to be all that universally-known, with the penny only just dropping for many after a viral post.

Tired Girl Apparel shared a photo of a top that said: “’You’re so funny!’ Thanks, I can’t have grapefruit.”

The caption added: “If you know…”

Naturally, it didn’t take long for the comments to become flooded with confused social media users.

“Wait am I not supposed to eat grapefruit?” one asked.

Someone else said: “Well this is how I find out.”

There's a surprising reason why some people shouldn’t eat grapefruit (Instagram/@tiredgirlapparel)

Offering up a bit of a clue, a third commented: “I Googled it because I didn’t know it, and I’m on 3 of the meds that say to avoid grapefruit.”

A fourth said: “Me being on Prozac and not knowing this.”

A fifth also pointed out that you ‘can’t have it on birth control pills either’.

Yep, it turns out grapefruit really doesn’t mix well with some medications – sometimes dangerously so – and many of us had absolutely no idea.

According to Johns Hopkins Medicine, grapefruit can block an enzyme that helps your body break down certain medicines.

“If this enzyme is blocked, too much medication could remain and build up in your bloodstream, causing too-high levels,” it explains.

A few years back, a study in the Canadian Medical Association Journal found that three times the levels of one blood pressure drug called felodipine was reported after patients had a glass of grapefruit juice, compared with a glass of water.

Dr David Bailey, one of the researchers, told the BBC: "One tablet with a glass of grapefruit juice can be like taking five or 10 tablets with a glass of water and people say I don't believe it, but I can show you that scientifically it is sound.

"So you can unintentionally go from a therapeutic level to a toxic level just by consuming grapefruit juice."

But which specific medications should make you avoid grapefruit?

Anti-depressants

The viral picture was in relation to antidepressants – specifically, sertraline, a type of anti-depressant known as selective serotonin reuptake inhibitors (SSTIs), which work by increasing the levels of serotonin in the brain.

It’s believed this doesn’t interact well with grapefruit juice, with the NHS warning: “Do not drink grapefruit juice while you're taking this medicine.

“Grapefruit juice can increase the amount of sertraline in your body and increase the risk of side effects.”

It’s believed that many medications don't interact well with grapefruit juice (R.Tsubin/Getty Images)

Harvard also lists Buspirone, Carbamazepine, Haloperidol, Haloperidol and Zolpidem as examples of other neurological and psychiatric medications that don’t go well with grapefruit.

The same goes for Benzodiazepines, which are used to treat anxiety and insomnia, including Diazepam, Triazolam, Midazolam, Flurazepam and Clonazepam.

Birth control

The contraceptive pill – especially those that contain oestrogen – can also be impacted by consuming grapefruit, with birth control app Emme explaining how it might actually increase the effectiveness in a pregnancy prevention sense, but also simultaneously increase the risk of side effects.

"The interaction is primarily due to compounds in grapefruit that inhibit the activity of an enzyme called cytochrome P450 3A4 (CYP3A4) in the small intestine,” it says.

“This enzyme is responsible for metabolizing many substances, including certain hormones found in birth control pills.

“When grapefruit or grapefruit juice is consumed, it can inhibit the function of CYP3A4, leading to a slower breakdown of estrogen. As a result, estrogen levels in the blood may increase.”

This can lead to an increased risk of oestrogen-related side effects like nausea, breast tenderness, headaches, and in some cases, an increased risk of blood clots.

Some types of birth control can be affected by grapefruit (Patricio Nahuelhual/Getty Images)

Statins

Statins are medicines that can help lower the level of low-density lipoprotein (LDL) cholesterol in the blood, and are often used to help lower the risk of heart attack and stroke.

But the NHS says: “Grapefruit juice can affect some statins and increase your risk of side effects.

“A doctor may advise you to avoid it completely or only consume small quantities.”

Anti-histamines

Grapefruit is also a no-go with some anti-histamines like fexofenadine, as it may make you more likely to get side effects – although it’s worth noting that the NHS actually also advises against drinking apple juice or orange juice, so grapefruit isn’t the only culprit here.

Other drugs that grapefruit can interact badly with also include drugs used to treat high blood pressure, immunosuppressants and corticosteroids – the latter of which are used to treat Crohn’s disease or ulcerative colitis.

However, Johns Hopkins Medicine added that, even within medicine classes, there can be differences.

“One pill might interact with grapefruit and another, similar medication for the same condition may not, so it’s always best to check with your doctor or pharmacist if you are in doubt,” it said.