6 Foods That Are Toxic If You Prepare Them Incorrectly

[INTRO ♪] You don’t usually think of sitting down for a meal as a death-defying adventure, even when your favorite home cook attempts a recipe way above their skill level. But some foods, even really common ones, are actually pretty dangerous if you prepare them incorrectly. Here are six of them. If you’re a fan of chili, you may have some
dried kidney beans in your pantry. But if you don’t cook them enough, they
can make you super sick. Many varieties of bean contain a protein called phytohemagglutinin, but uncooked red kidney beans have some of the highest levels. Phytohemagglutinin, or PHA, is a type of lectin: a protein that binds carbohydrates. Scientists aren’t sure exactly what lectins
do in bean plants, but we know they’re important. We know a lot more about what PHA does to
animal cells. For instance, it makes red blood cells clump together, so it’s been used in medical research to help separate the components of blood. It also interacts with white blood cells and
is used in immunology research. And if you eat PHA, it binds to the cells that line your gut and reduces their ability to digest and absorb food. This causes cramps, diarrhea and vomiting. The wild thing is you only have to eat 4 or 5 improperly cooked kidney beans to make you sick. Boiling kidney beans breaks down the PHA,
because heat can disrupt the bonds within the protein. And without that molecule, they’re safe to eat. Since canned kidney beans are boiled during the canning process, you don’t need to worry about them. But if you’re cooking dried kidney beans, it’s recommended to soak, drain, and then boil them for at least 30 minutes. And you need to make sure they get hot enough, because sometimes slow cookers, which cook at lower temperatures, don’t do the trick. Humans like their carbs. Foods like rice, potatoes, and wheat are staples
in many parts of the world. But in many tropical areas, cassava is king. Cassava is a root vegetable, kind of like
a carrot, and in many ways it’s a great crop. It’s very hardy, can grow in poor soils,
and doesn’t need much water. But cassava also contains chemicals called linamarin and lotaustralin. These chemicals seem to help protect the plant from herbivores and transport nitrogen, which is a crucial nutrient. But they’re also cyanogenic glycosides, which means that they’re converted into cyanide-containing compounds when digested. And cyanide is bad news for your cells. It interferes with cellular respiration and prevents your cells from making ATP—the molecule they need for energy. But if you process cassava properly, you can
get rid of them. Linamarin makes up more than 80%, so we’ll focus on that, although lotaustralin works similarly. There are different techniques depending on the food you’re making—a mashed potato-like dish will be different than dry flour. Some varieties of cassava have more cyanogens
and need more processing. And some kind of pulverizing is usually involved. This is important because cassava cells contain both linamarin and an enzyme that breaks it down—they’re just separated in different compartments. So if you smash up the cells, the linamarin
gets mixed with the enzyme and broken down. This produces hydrogen cyanide, but it vaporizes into the air. The problem is that processing cassava properly
is a lot of work. And when there are food shortages, people
sometimes take shortcuts. Chronic exposures to low levels of cyanide from cassava can lead to problems with the thyroid gland and nerve damage that can cause unsteady movement. Exposure to higher levels causes a disease called Konzo, which involves permanent paralysis
and sometimes death. Scientists have tried to genetically engineer varieties of cassava without linamarin to reduce the need for processing and prevent poisoning. But they found that without linamarin, cassava requires lots of fertilizer to grow, and this makes it a less practical crop. Ackee is the national fruit of Jamaica and is part of the national dish: ackee and saltfish. It’s not really a sweet fruit. It has a mild flavor and creamy texture, and it’s usually cooked with savory foods like fried onions, peppers, and tomatoes. Ripe ackee fruits don’t pose any hazard, but unripe fruits contain an amino acid derivative called hypoglycin A. Levels of this chemical drop naturally as the fruits ripen. There hasn’t been much research on why this fruit contains hypoglycin A, but it’s there, and it’s bad for you. When ingested, hypoglycin A disrupts the body’s ability to metabolize fatty acids and amino acids. Basically, this means you’ll have trouble breaking down food into glucose, and that can cause low blood sugar, or hypoglycemia. When your body breaks down hypoglycin A, it’s converted into a different chemical called methylene cyclopropyl acetic acid. This is also toxic, and leads to depletion of glycogen—your sugar stores—which means … even less glucose. Symptoms of hypoglycin A poisoning include vomiting, which is how the associated disease got its name: Jamaican vomiting sickness. And enough unripe ackee fruit can cause seizures or even death, which are much worse. Rhubarb is a hardy plant that even gardeners
with a black thumb can’t kill. Its stems have a sour flavor, and they make
a nice pie filling with sugar and some strawberries. But you probably want to stay away from rhubarb leaves—they contain high levels of a chemical called oxalic acid. Lots of plants produce oxalic acid, even other
veggies we eat. It binds to calcium to help them
regulate mineral levels. Some plants also use it as a defense against herbivores, because oxalic acid and calcium can form needle-shaped crystals that irritate soft tissues. Rhubarb leaves don’t have crystal needles, but they do contain enough oxalic acid to make you sick if you eat a lot of them. Oxalic acid makes it harder for your body to use calcium to do things like strengthen bones. Instead, your body tries to excrete the bound up calcium, which can glob up to form kidney stones. And kidney stones eventually have to pass
through the same tube as your pee… Ow. Eating too much oxalic acid can also lead
to vomiting, diarrhea, or convulsions because your muscles and nerves need calcium to function. During World War I, food shortages in Europe
led some people to eat lots of rhubarb leaves. One medical case report even describes a woman
who died from it. Although doctors today speculate that there was probably something else going on besides rhubarb poisoning, because it’s not that potent. So rhubarb kind of has a bad reputation because
of this history. But you’d have to eat many pounds of rhubarb leaves to get really sick, and you probably wouldn’t want to, anyway. According to people who’ve tried eating
them, they’re not exactly delicious. So stick to the stems. Have you ever noticed that cashews are never
sold in the shell like walnuts or almonds? Also, they’re pretty much only pre-roasted,
not completely raw—no matter what labels say. And that’s for your safety, because their shells contain anacardic acid, which is closely related to urushiol. Urushiol is the oil that causes that nasty rash from poison ivy or poison oak, and anacardic acid does the same thing. It turns out that the cashew tree is in the same plant family, and scientists believe these compounds help keep microbes out of damaged plant tissues. These chemicals don’t protect them from
being eaten, though. Birds, deer, and lots of critters snack on
plants like poison ivy. But humans are special. We’ve got these nifty thumbs, we overthink things, and our immune systems get freaked out by urushiol and anacardic acid. There’s technically nothing dangerous about these compounds. They don’t harm your body. But when they’re absorbed by your skin, they’re converted to another molecule that binds to proteins on your skin cells. This makes your immune system think your skin cells are dangerous invaders, so immune cells are recruited to attack. This pointless battle results in the redness, itching, and oozing blisters known as contact dermatitis. And your gastrointestinal tract is lined with epithelial cells, which are the same kind that make up your skin. So if you eat improperly processed cashews, the anacardic acid will cause a similar reaction inside you, or even a rash around your anus. No thanks. Pufferfish is a high-end delicacy in Japanese,
Korean and Chinese cuisine. In Japan, it’s frequently served fresh and
raw as sashimi. But if your chef doesn’t prepare it correctly,
it could be your last meal. In fact, chefs in Japan need years of training and a special license to prepare pufferfish, because they need to remove certain organs very carefully. Some species of pufferfish contain a neurotoxin called tetrodotoxin—especially in their liver and ovaries. Tetrodotoxin blocks the sodium channels in
the cell membranes of your nerve cells. That prevents the nerves from transmitting
electrical impulses. And with no nerve impulses, your muscles stop moving. You need muscles to breathe, so this means you’ll suffocate, and your heart may even stop. Even a tiny amount of tetrodotoxin—just
1 or 2 milligrams—can kill an adult human. Which makes tetrodotoxin one of the deadliest poisons around. It’s much more potent than arsenic or cyanide,
for example. But pufferfish might not even make tetrodotoxin
themselves. The science isn’t settled, but there’s evidence that the fish get the toxin from bacteria they eat with their food. Or it may even be produced by
bacteria living inside of them. Scientists aren’t entirely sure why pufferfish
accumulate tetrodotoxin. There’s some evidence that it might serve as a chemical signal called a pheromone, and help attract mates. Or it may help with protection, since the taste of even tiny amounts of the toxin in the water seems to deter predators. But scientists need to do more research to
confirm that. Either way, it doesn’t deter seafood-loving humans. So even if you’re not an adventurous eater, your meals may be more perilous than you imagined—but only if they’re not prepared correctly! But whether or not you’re an adventurous eater, by watching SciShow you are an adventurous learner! And that includes our President of Space today, Matthew Brant, whose support lets us make videos about all kinds of science and release them for free for everyone to watch! So thanks, Matthew, for supporting SciShow! And thanks to the rest of our patrons on Patreon, too. [OUTRO ♪]

100 thoughts on “6 Foods That Are Toxic If You Prepare Them Incorrectly”

  1. Like rhubarb leaves, the fruit known as Delicious Monster, when unripe, also contains oxalate crystals, though in even more potent form. Eating the unripe fruit can cause damage to the esophagus and mucosal membranes of the digestive tract due to the crystals.

  2. So basically…boil your kidney beans, properly prepare your cassava, make sure your ackee fruit is ripe, cut the leaves off your rhubarb, and shell and roast your cashews, and you should be fine. As for pufferfish, it's probably best not to bother.

  3. My great-great grandmother did actually die from eating rhubarb leaves because of food shortages and because there was a rumour that it was good food. She wanted to set a good example for the rest of the family and ended up being the one who ate most, which was too much.

  4. You missed the common potato. The green spots contain a poison that can kill you if you eat enough. That's why you shouldn't eat potatoes that have started to sprout.

  5. Ok there is a genuine question that HAS to be asked…

    Is S.R. Foxley ok? Are they alive still? Where is my president of space?

  6. This is why you're supposed to soak all dry beans overnight and then pour off the bean water before cooking. Preferably by boiling them in a fresh batch of water

  7. The kidney bean thing sounds like it might have been an adaptation to prevent being eaten by mammals – or more specifically, to be ingested, mixed with nutrients briefly, then spat back out on the ground, where they can germinate easier.

  8. I can't believe you didn't mention potatoes. Potatoes are a great food because they can be stored for a long time. The problem is that if you store them too long, then they will start to germinate. When they do that, they start to produce toxins and can be dangerous to eat. It's easy to tell though because they turn green.

    By the way, if you have a potato that's starting to geminate, don't throw it out. Plant it, and in a month or so you'll have like 5 edible potatoes.

  9. I just realised I've eaten cassava lately. And i have been having diarrhea and stomach pain for the last 24 hours, should i get myself check up?

  10. I’ve eaten raw cashew fruit before. I didn’t get sick, because it was so bitter I couldn’t handle more than a small nibble.

  11. Cashew fruits are actually pretty good for making a fresh drink, and most peopl know that latex from trees (most trees) is not good for you.

    In the comments, someone mentions manchineel (beach apples) – you should make a video on killer trees! Manchineel and Meopium Toxiferum (we call it chechen)are some hard-core, left-wing;right claw, world-hating killer trees.

    Finally – bread made with "bad" wheat can give you ergot poisoning.

  12. Fishing is responsible for almost half of the plastics in the oceans. Animals are not food.

  13. Never eat puffer fish outside of japan. Whether it is considered poison or not. Mistakes have happened. Also, dont eat puffer fish in japan unless it is in a proper, top of the line restaurant. That's where the chefs that are skilled in the art of serving fugu are.

  14. wait wait wait… so. did someone already try to use uncooked kidney beans as diet? No i wont try it. I kinda have a Feeling there is someone who already died from trying though

  15. Of course all poisonous foods need to be prepared correctly otherwise they're not food, anyone remember the (pitohui or rubbish bird)

  16. Boil your beans for at least 30 minutes at 100 °C/ 212 °F before the low and slow simmer for safer eating.

  17. when i was three i ate some cashew, but i did not know that it wasnt good for you, the result was a severely burning red mouth.

  18. You forgot to include bitter almonds. If eaten uncooked you die of cyanide poisoning. Also dont eat apple seeds, same thing

  19. 1. Kidney beans (boil for 30 mins to fix)
    2. Cassava (pulverize it to fix)
    3. Unripe Ackee fruit
    4. Rhubarb leaves
    5. Cashew shells
    6. Pufferfish (remove specific organs carefully)

  20. Humans should not eat a plant based diet. We are hyper-carnivores. See Dr. Salisbury's 1888 book on researching the 'perfect' diet for humans. Don't give anyone diet advice until you do.

  21. Well, there's no scientific proof that dietary calcium strenghten the bones, so You might correct that part… It's magnesium, vitamin D and maybe vitamin K that have some proof for increasing bone density. Dietary calcium is mainly use as "free" electrolyte, for nerve signaling especially with muscles – its necessary for muscle contraction etc.

  22. I LOVE CASSAVA, as any Brazilian, I eat cassava one way or another daily. Also, the majority of the breeds are only mildly toxic, and only if you set them raw (raw is basically eating a form of bitter and hard squashy wood)


  24. This guy is way better than the usual skinny girl ….. at least with ihm I watch the video till the end !

  25. The process for preparing tapioca is really freaky. Starts off as a toxic plant which needs to be boiled to make safe (and delicious).
    …when i think of that, it makes me wonder. Did they just keep testing it until nobody died?!? Huuuuumans. WTF?

  26. you forgot about nutmeg lol only 3 teaspoons or so can kill you. (Only reason it’s still widely available is because almost nobody with eat that much nutmeg at once)

  27. So what you're saying is, if I want a day off of work, just swallow like 6 uncooked kidney beans. Neat!

  28. fugu is less toxic when raised in old renovated hot springs. Some companies are just making the fish safer probably because regulations on preparation were loosened a few years ago. It's also just income for small towns whose populations left for the major cities.

  29. In japan, they have successfully aquacultured tetrodotoxin free fugu. Its just not on the market last i heard.

  30. WAIT WAIT WAIT here peoole usually steam cassava or steam then fry them does that damage the toxins too??? so far as I remember I never see anyone getting sick from cassava here, and they are very popular snack in my country

  31. I ate raw kidney beans with hot sauce decades ago when I was on a raw food kick. It was repulsive. I guess I threw up before I could digest them, which saved my life.

  32. Sometimes I ask my self if having a trach and a gastric tubes is worth it. Then I watch videos like this and realize that I don’t have to worry about any of these food because mine is basically modified milk of sorts made for medical nutrition so I’m good.

  33. Before the vid
    I bet I haven't and likely wouldn't eats any of these
    Edit: Cashews I ate those in a pack before ofc

  34. Soy beans. If not prepared properly they produce EXTREME flatulence. It's not dangerous unless you develop an obstruction, but it is uncomfortable… and funny. This is why you'll rarely find raw soy bean in any store. Consumers can't be trusted to prepare it properly without poisoning themselves.

    I received an improper batch from Costco and farted almost continuously for about 6 hours. Not like one or two farts a minute. No pauses at all. Continuously for six hours.

    It might make a hillareous if dangerous practical joke.

  35. its interesting that preperation of many otherwise poisonous plants or mushrooms seems pretty universal. cooking it for a long time, breaking it up and soaking it in water for a long time or boiling it and changing the water several times. mushing it into a pulp for enzymes to work is probably the only exception but easily discovered since its a common preperation method. and if all else fails you can ferment it too.

  36. Here in Brazil, there is a dish wich is popular on the north called “maniçoba”. Basically its boiled cassava leaves, FOR 3 WHOLE DAYS.
    I wonder how the heck dey got to that number…

  37. cassava make very taste cakes here i love them also the pufferfish i eat a lot of it when we are visiting our fishingfolks relatives its very tasty unlike any other fish ive eaten especially when cooked with coconut milk and lemongrass leaves with papaya also.

  38. Casava??? Here in brazil we call for many names, like:
    ●Mandioca (south of Brazil)
    ●Aipim (midle of brazil)
    ●Macaxeira(nort of brazil)

    I never have hearing cassava .

    And caju's fruit make the best juice. And the seed is much better than peanut.

  39. It's really improbable to cook kidney beans and cassava wrong. They're hard as hell, you put them in the pressure pan and they'll cook pretty well.

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