In North America, we get stuck thinking that there are only about a dozen “normal” fruits because those are what are accessible to us. We grab bananas, apples, oranges, grapes, berries, melon – maybe a pineapple or a mango once in a while, or a kiwi, but that’s about as wild as we get.

There are some crazy fruits out there in the world, of course, but what if I told you the seemingly innocuous grapefruit was one of the weirdest?

To get there, we need to wander through some facts and history, so bear with me, ok?

Citrus fruits are native to warm, humid climates, and originally resided in those portions of Asia. Climate change pushed species like the citron, pomelo, and mandarin all over the world, and several others spread out over Asia.

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The citron, pomelo, and mandarin are most important, though, because basically all citrus fruits are derived from them still to this day – sort of like the primary colors of citrus fruits.

Grapefruit, for its part, is a mix between a pomelo and a sweet orange (a hybrid of a pomelo and a mandarin). It was also not first found in Asia, but half a world away in Barbados sometime in the mid-1600s.

Europeans had planted citrus trees all over the West Indies and hybrids were appearing willy nilly. No one was documenting them at the time – what they originally planted or what later mixed with which – and no one was taking measures to avoid hybridizing, so it was happening all over the place.

The unintentional fruit that would become the grapefruit wasn’t even called by that name until the 1830s (that we know of), and was before that probably referred to as a “shaddock,” or the simple word for “pomelo” in the area.

Writer Griffith Hughes referred to a shaddock tree that grew a “golden orange,” or the “forbidden fruit” in 1750, and since the grapefruit was the most famous and popular citrus fruit in the West Indies, people imagine it was what he was talking about in his writings.

Some researchers believe a “golden orange” was indeed a grapefruit, but that the “forbidden fruit” was some other hybrid that has since been lost to time.

The name grapefruit is also up for debate, with some believing it harkens back to a 1664 Dutch physician describing the citrus in Barbados as “tasting like unripe grapes” while others point to John Lunan, an 1814 plantation owner from Jamaica, saying the fruit was named “on account of its resemblance in flavour to the grape.”

It’s important to note that grapes as we know them didn’t exist there until the 18th or 19th century – before that they only had sea grapes, which aren’t grapes at all but a kind of buckwheat, and are sour and slightly bitter (just like a grapefruit).

The grapefruit made its way to America in the 1820s, when Frenchman Odet Philippe hopped over to Pinellas County, Florida. He loved the grapefruit and planted huge swaths of it, even gifting grafts to his new Native American neighbors so they could grow it, too.

Then another grapefruit devotee, Kimball Chase Atwood, moved to Tampa bay and planted his own grove of trees – around 16,000 of them, to be exact.

Grapefruits would rather not be contained or cultivated, though, and turned pink all on their own – Atwood patented the Ruby Red grapefruit in 1929, making a fortune even though the fruit had hybridized itself in the wilderness.

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Which is all very interesting, but the innovating breeding properties doesn’t necessarily qualify the fruit as weird.

What clinical pharmacology researcher David Bailey found in his lab in 1989, though, definitely does – because what he discovered is that grapefruit is one of the greatest foes of modern medicine (when it comes to adversarial foods).

“The hard part about it was that most people didn’t believe our data, because it was so unexpected. A food had never been shown to produce a drug interaction like this, as large as this, ever.”

Bailey works for the Canadian government testing various medications to see how humans react to them. He was working on a blood pressure drug in 1989 and trying to see whether or not it reacted to alcohol. The alcohol had to be disguised for the double-blind study, though, and he and his wife found that nothing hid the taste of booze like grapefruit juice.

The control group got grapefruit juice and the experimental group got grapefruit juice and alcohol, but the results were nothing Bailey – or anyone – could have predicted.

“The levels [of the drug] were about four times higher than I would have expected fo the doses they were taking.”

And this was true of both the control and the experimental groups.

The only thing he could imagine affecting his results was the grapefruit juice, which no one had thought to test in reaction with that particular drug (or any drug at all, for that matter).

Bailey decided to test the theory on himself.

“I remember the research nurse who was helping me, she thought this was the dumbest idea she’d ever heard.”

It might have been a dumb idea, but it was right – the grapefruit was screwing with something, somehow quintupling the drug in his system compared to what he had taken.

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When drugmakers start to formulate dosages, they consider the work of an enzyme called cytochrome P450, which basically filters out parts or all of various substances before they can reach your bloodstream. With drugs, it can be as little as 10% of what you ingested.

Grapefruits contain a compound called furanocoumarins, which protect the fruit from fungal infections, and guess what they do to those cytochromes?

Take them out of the game, that’s what.

When you eat a grapefruit those P450’s are destroyed, and it takes your body around 12 hours to make more. So, for those 12 hours, every drug you take will get into your bloodstream with nothing to block some of it.

You can see how this could potentially induce an overdose, since drugmakers assume you have those enzymes taking down your dosage. If you don’t, all bets are off.

There are actually a bunch of very common drugs, like Xanax, Adderall, Zoloft, Lipitor, Cialis, and even things like Prilosec or Tylenol, that can and are easily affected by even small amounts of grapefruit or grapefruit juice.

For some of those, taking a higher dosage once in a while is no big deal, but for others, it certainly can be, according to Bailey.

“There are a fair number of drugs that have the potential to produce very serious side effects.

Kidney failure, cardiac arrhythmia, gastrointestinal bleeding, respiratory depression…”

Basically, there are definitely people who have died because they decided to have a grapefruit for breakfast.

The FDA typically does not place warnings about this potential interactions on the labels of any drugs, though you can find some mention of it if you go to websites dedicated to individual prescriptions.

The interaction extends to all bitter citruses – the ones descended from the pomelo.

Grapefruit contains a bunch of health benefits, like loads of Vitamin C, but if you’re someone who takes drugs every single day, you might want to have a chat with your doctor before you add it to your daily diet.