Previous: No, Your Dog Doesn't Think You're the "Alpha"
Next: The 5 Strangest Lakes on Earth | Nature Compilation



View count:210,448
Last sync:2022-11-23 13:00
In the 90s, patients displaying symptoms similar to, but not exactly like Parkinson's Disease left doctors scratching their heads. But when they took a look at their patients' diets, they found the culprit in the form of a popular and tasty fruit with a dark secret.

Go to to try their course on Cryptocurrency. The first 200 subscribers get 20% off an annual Premium subscription.

Hosted by: Michael Aranda

SciShow has a spinoff podcast! It's called SciShow Tangents. Check it out at
Support SciShow by becoming a patron on Patreon:
Huge thanks go to the following Patreon supporters for helping us keep SciShow free for everyone forever:

Kevin Bealer, Jacob, Katie Marie Magnone, Charles Southerland, Eric Jensen, Christopher R Boucher, Alex Hackman, Matt Curls, Adam Brainard, Jeffrey McKishen, Scott Satovsky Jr, James Knight, Sam Buck, Chris Peters, Kevin Carpentier, Patrick D. Ashmore, Piya Shedden, Sam Lutfi, Charles George, Christoph Schwanke, Greg, Lehel Kovacs, Bd_Tmprd
Looking for SciShow elsewhere on the internet?
Thanks to Brilliant for supporting this episode of SciShow.

Go to to check out their course on Cryptocurrency. [♪♪♪Intro♪♪♪]. In the 1990s, doctors noticed something unusual happening in the islands of Guadeloupe, Guam and New Caledonia, as well as in Caribbean communities in the UK.

Patients were presenting with stiffness, difficulty with movement, and dementia -- as well as tremors and hallucinations. These symptoms were similar to what we see in Parkinson's disease, a progressive condition that affects motor and mental abilities. But not quite the same.

And doctors were able to tie the condition to… a fruit. These patients were diagnosed with atypical parkinsonism, a cluster of conditions that are similar to classic Parkinson's disease except that they don't respond to the same drugs, and may progress more quickly. Because atypical parkinsonism is, well, atypical compared to classic Parkinson's, doctors suspected that something in the patients' environment was to blame.

So they looked at their diets and discovered they all had a taste for a spiky green fruit called soursop. The scientific name for soursop is Annona muricata, and it goes by a number of aliases: graviola, guanábana, corossol, and Brazilian pawpaw. It's said to have a mild pineapple-y, banana-y, strawberry-y flavor.

And lots of people love it. But unfortunately, many parts of the plant and fruit contain a low dose of a neurotoxin. Scientists suspected a toxin in soursop might be harming people's dopamine-producing neurons.

Dopamine is a neurotransmitter involved in movement, and when those dopamine neurons die, it can lead to Parkinson's. So in a 2002 study, researchers put extract of soursop root bark into a culture of dopamine neurons. After 24 hours, half of the neurons were dead.

The soursop toxin had actually induced programmed cell death in those neurons. Researchers later identified the neurotoxin responsible as annonacin, and it's not just in the plant's root bark. There are about 15 milligrams of annonacin in each soursop fruit and about 36 milligrams in a can of soursop nectar.

In a 2004 study, rats given injections of annonacin developed brain lesions within a month. Though, those rats got intravenous infusions of the purified chemical, which isn't necessarily the same as eating fruit -- plus, rats don't always respond to toxins the way we do. Still, studies like these have established that this chemical isn't the safest thing for us.

There's a twist, however. Because annonacin isn't the only thing hiding out in this fruit. Scientists have identified other, totally separate chemicals in soursop that may protect dopamine neurons and help treat Parkinson's.

The chemicals are called tryptamine-derived alkaloids. They're similar in structure to melatonin, a hormone involved in sleep regulation that can have protective effects on dopamine neurons. In a series of studies, a team based in France synthesized compounds based on ones found in soursop, modified their chemistry, and tested them for their ability to protect dopamine neurons from damage.

Their most promising candidate was a molecule they called PPQ. And it helped to counteract the loss of dopamine cells in a mouse model of Parkinson's. More trials will be needed, but the researchers say PPQ is a promising candidate for Parkinson's treatment.

So soursop – a widely loved but slightly toxic food that can cause Parkinson's symptoms – could also lead us toward a treatment for Parkinson's. Talk about a frenemy. Speaking of frenemies, what's the deal with cryptocurrency?

And what the heck is blockchain? Brilliant's course on cryptocurrency can help you understand how it all works -- and whether it's friend, foe, or both. It turns out there's a lot of math to learn there.

And Brilliant has lots more math courses if you're looking to learn even more plus science, engineering, and computer science. The courses are designed by educators and lifelong learners from prestigious universities around the world, all to help you sharpen your math and science skills. Right now, the first 200 people to sign up at will get 20% off an annual Premium subscription to Brilliant.

And by checking them out, you're supporting SciShow, too -- so thanks. [♪♪♪Outro♪♪♪].