7 Scientific Urban Legends Debunked!

Hey smart people Joe here – stay tuned for a special announcement after the video. So I used to have this shirt. I know at least one of you was watching back
in 2013… Hey Kyle. For the rest of you are probably wondering
the same thing as me. What’s up with the hair? What this shirt means is that the microbes
in and on our bodies outnumber our own cells. Most common figure is by 10 to 1. Except… that’s not true. It’s a scientific urban legend. Yet this factoid continues to be shared and
recited as fact. I’m guilty of it too, I mean, my old video
is called “You’re Mainly Microbe” and it’s literally centered around this erroneous
factoid. It turns out that urban legends like this
are surprisingly common, even in science, and how they begin and the reasons why they
persist can teach us a lot about how science works, and when it doesn’t. At some point the 10-to-1 bacterial to human
cell ratio became “common knowledge”. Common knowledge is information that the average,
educated person in some group–the general public, scientists, whoever–accepts as reliable
without having to look it up, like how we all know that water freezes at 0˚C. We all know that, right? Somewhere along the line, people stopped asking
where this “common knowledge” came from. There are countless facts in science that
have become common knowledge. I mean, if research papers cited an original
source for every single fact they presented, it would be an absolute mess. Say you wrote a paper about synthesizing some
new chemical? Do you have to cite a paper that proves chemicals
are arrangements of different atoms? Ok, then do you need to cite something to
prove that atoms exist? Maybe Einstein’s 1905 paper on Brownian
motion? Or do you have to go back to John Dalton in
the early 1800s? You can see things get ridiculous pretty fast. But! Sometimes things that aren’t true become
common knowledge, or they’re corrected later, but the new information fails to replace the
old idea. Here’s an example: I wouldn’t be surprised
if at some point in your life, you probably heard that spinach was a particularly excellent
source of iron. I certainly remember being taught that, I
can’t even remember where. And–you can probably guess where I’m going
with this–it’s not true. In 1981, a biologist named Terry Hamblin studied
historical science papers and realized the iron content in spinach was misreported, thanks
to a misplaced decimal point, way back in the early 1900s. Except he didn’t cite a source for the misplaced
decimal point story either. And it turns out that THAT’s a myth too. Turns out the earliest old-school measures of iron in spinach were waaaay too high, and wrong, but because of contamination, not a misplaced decimal point. It’s science! Details matter! Spinach actually does contain large amounts
of iron, as much as red meat in some cases, but it also contains compounds that make the
iron it does have harder for us to absorb. So it’s not an exceptionally great source
of iron. Incidentally, it turns out “Popeye” creator E.C. Segar chose spinach as the sailor man’s food of choice for its high vitamin A content, not because of iron. It’s another case where the correction never
seems to spread as wide as the lie, and it’s a good reminder that a good story is not necessarily
a true story. And I’m willing to bet that at some point
in your life, you’ve taken vitamin C to help cure or prevent a cold. Yeah, that’s not true either. That myth traces to legendary scientist Linus
Pauling. In 1966 Pauling was convinced by a random
dude named Irwin Stone that taking large doses of Vitamin C would help him live longer, and
Pauling started taking doses equivalent to 1800 glasses of orange juice every day, and
wrote books and articles claiming that the colds he had suffered from his whole life
“no longer occurred”. Even though Linus Pauling won not one but
two solo Nobel Prizes in his life, dozens of studies since have proven he was wrong,
about vitamin C. It doesn’t significantly affect colds, and the only disease it definitively
prevents is scurvy. Yet somehow the cold myth still continues
today. Or maybe you’ve heard that you lose most
body heat through your head? That urban legend goes back to one military
study in the 1950s where people were left out in the cold with no hats on. I mean, you’re gonna lose most of your body
heat through your head if that’s all that’s exposed. Today scientists know the amount of body heat
you lose depends on the total surface area exposed, but parents everywhere are still
making sure you don’t leave home without a hat. You also don’t need to drink 8 glasses of
water a day. That urban legend probably goes back to one
set of dietary recommendations for water intake from 1945. Except many people who cited that number ignored
the part where it said most people get a majority of the water they need from food. It’s important to stay hydrated, but 8 glasses… I mean, like what size of glasses even?! And one of the most famous is that sugar causes
hyperactivity in children. This one seems totally logical, but more than
a dozen randomized controlled trials have failed to detect different behavior between
kids given large doses of sugar and kids who weren’t. That’s right, the cake is actually a lie! Turns out when parents even think their children
have been given a drink containing sugar (even if it’s actually sugar-free), they tend
to think their kids are being hyperactive. This particular urban legend traces its origin
back to California allergy doctor Benjamin Feingold in 1973, who with little to no evidence,
recommended removing artificial colors and flavors from the diets of hyperactive children,
and I guess people were like “why not sugar too!” I mean, kids are just kids, and they’re
gonna go nuts some times. Let’s go back to that 10-to-1 mainly microbe
cell number from the beginning. In 2010 a couple of researchers went on a
deep dive to find the original source, and the paper cited most often was this one, from
1977. It states the human body contains 100 trillion
microbial cells and 10 trillion of its own cells. Ten to one. Scroll down to reference #70 and we find the
source of the 100 trillion microbial cell number is this 1970 paper by Thomas Luckey,
which, when we read the paper, turns out was just a back of the envelope estimate, and
wasn’t based on any actual experiments. This has nothing to do with the rest
of the video, but I just have to mention Dr. Luckey was literally an honorary samurai,
which is awesome And going back to the original 1977 paper,
the human cell number comes from reference #27, a 1970 textbook by biologist Theodosius
Dobzhansky. I dug through the internet to find a copy
of it, and right there in chapter 1, with absolutely zero supporting evidence, is the
claim that a human body contains ten trillion cells. And there you have it. A back of the envelope estimate combined with
a totally unsupported approximation to create the very wrong and very widely shared fact
that human cells are outnumbered by microbes 10-to-1. Right about now you’re probably wondering
what the real numbers are. First, the original estimate for microbes
living inside us was calculated using the volume of the entire lower intestine. But the vast majority of your body’s microbes
live in your colon, which is only a portion of that volume. And yes, that’s where your poop is made. Using a more accurate volume of the average
colon–409 milliliters–and the number of bacteria we typically find per volume of poop,
in 2016 researchers calculated that your inner microbial population is… drumroll please… 39 trillion. Not 100 trillion. And as for the number of cells in the human
body? This is a seemingly simple question that you
might assume we biologists have known for a long time. But the truth is, until very recently, no
one really knew. Over the past couple centuries, estimates
have ranged from 5 billion to more than a quadrillion cells in our body. What makes it so difficult is that cells in
our body vary hugely in size and how tightly packed they are, so the only way to get a
good count is to estimate each organ individually. And that’s what a group of researchers did
in 2013. Based on actual evidence, their new number
is… 37.2 trillion cells in the average human body. That makes the ratio of microbe to you more
like 1 to 1… pretty much even stevens. Amazingly, although most of your mass comes
from muscle and bone cells, by sheer number, red blood cells make up more than 80% of the
cells in your body. bit more in favor of the microbes. But remember how I said almost all of your
inner microbes live in your colon? Well, you lose almost a third of them every
time you have a bowel movement, so every time you poop, the ratio swings in your favor,
at least for a few hours until they get their numbers back up. Doesn’t make as catchy a shirt though… Things we consider common knowledge can be
based on bad information, and despite the amazing power of science to correct its own
mistakes and uncover better and better knowledge over time… that good knowledge doesn’t
always spread out and replace the bad knowledge. So how do these scientific urban legends continue
to persist? More scientific journals exist today than
ever before, and we’re doing more science today than ever before. Most of that science is peer-reviewed, but
peer-reviewed doesn’t always mean something is true. If one false citation makes it into the system,
it can set up a domino effect as other people cite that bad fact instead of verifying the
original. The solution? Well, for you out there in the “general
public” at least, wherever you can, even if you think something is common knowledge,
try to learn where it came from. You might be surprised by what you find. But that’s easier said than done, because
most published science today isn’t freely available, at least not legally. Most scientific research today sits behind
paywalls, so even if you wanted to check a source, you couldn’t. Then what about this? Now, it’s easy to dump on Wikipedia. Anyone can edit it, and I mean, they have
en entire page titled “Wikipedia is not a reliable source”. It’s a paradooooox… wait, why don’t
I have a wikipedia page? Come on Kyle. But Wikipedia represents a collection of our
common knowledge. It’s the most widely read and widely accessible
information source on Earth. And at least one study has shown that Wikipedia
pages are more likely to cite scientific sources that are freely available. This isn’t an ad for Wikipedia, it just
seems like if you want to get good science out to the broadest audience, making it freely
available is not a bad place to start. The point, to me at least, is pretty clear. If you want common knowledge to be true, you
have to let true knowledge be common. Every one of us carries quite a few pieces
of incorrect knowledge in our heads. That is nothing to feel bad about. What matters is being comfortable enough with
the idea of not knowing everything that you’re able to replace bad knowledge when you find
better knowledge. Stay curious.

Comments 100

  • BIG EXCITING ANNOUNCEMENT!! We are now on Patreon! Come join our family: https://www.patreon.com/itsokaytobesmart
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  • Since you give a hint of it, could you make a video explaining why the peer reviewed scientific articles are not available to most people. Or instead of why, describe the history of scientific publication.

  • Paywall? Either use the Unpaywall extension or send a respectful e-mail to the writer of the paper and get a copy for free.

  • Spinach was the way E.C. Segar comically wrote about marijauana. This is not a myth

  • What is your experience with ascobric acid. How have you experimented with it. Oh the way you explain water intake, again, you don t really know what you re talking abut, and for all the above and your video, you are just to young, you are regurgitating book knowledge that for the most part is not based on experience over decades of your life. So much for edgumacation.

  • subscribe to (Chadi Hamish) and give a like IF you love GOD
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  • 'Never trust a fart"… Albert Einstein

  • Wikipedia Article on why wikipedia is not a reliable source. Wow, that's a paradox. lol..

  • Although vitamin C might not directly cure colds isn't it true that it supports the immune system overall

  • No Spinach was weed in old Jazz slang ,,, why you think he partook it via his pipe ?

  • How about that stupid one about humans only using 10% of our brains?

  • Can you do a segment on the placebo effect?

  • I am afraid of this guy

  • oh damn!
    I drink from 10 to 15 glasses of water everyday! (Around 25cl per glass). But all because I keep being thirsty. I am sick?

  • But I've seen children on sugar! 😮

  • What if it's not okay to be smart??I know it's a common knowledge, but is it scientifically proven that it's okay to be smart?😜

  • science is like miths
    the science try to explain things
    but there are some things that science cant explain..

  • You GUESS people included sugar with artificial colors and flavors!!!!  I guess it is also okay to be an idiot!

  • Great video

  • Ha, another punch in the face to Scientism!!!

  • "You're more you after a nr. 2" Catchy shirt slogan, and more accurate.

  • Great video! Thank you for making me smarter!

  • The portajohn spliced in Rambo. LOL

  • Dude that rocky clip was AMAZING!

  • "We all know water freezes at 0° C"

    Americans: *sweating

  • Ask for access to papers behind a paywall, at least in the US, a local or state library card may allow you access through. Most libraries give the cards to all comers that are local to the area. Some to anyone with an ID. And even with no card, many allow access when simply on their Wi-Fi.

  • Exclusive Patreon content!?!?!…so…a paywall… 😉

  • i understand this video is about you being wrong or something but that thumbnail

  • May I know what biological strength for a person person always score in basketball shooting? Obviously not just muscle..

  • 11:05 mhm.. Aaron Schwartz tried that… one russian is still succeeding at that – against all odds…

  • Large doses of vitamin C cause diarrhea; Pauling probably didn't get sick because he was stuck in the bathroom and therefore wasn't exposed to the general public and its germs 😆

  • Can not wearing a coat in the winter make you catch a cold or the flu?

  • You are correct in this video mostly. 99% or more scientists today are "fraudsters".
    Society runs on "reputation" and "status" rather than facts.
    I didnt get any postdoc after PhD, but my batchmates got and became scientists. Their qualification is similar, skill levels are similar. However, when I applied to any scientist, he asked about my publication. I had no publication during my PhD, which was actually a fraud PhD (from my standards), because my PhD guide used to go to temple ……..means faith..rather than experiments……whatever I did under her guidance I was compelled by her for her point of interpretation without any actual empirical analysis. So, naturally she scolded, bullied, threatened…and………………and somehow that PhD degree was given to me.
    My batchmates… they got publications,, their guides…with them their behavior was conducive…and in fact the publications that they got, were from the lab where a shared author ship is given. So if there are 4 members in the lab then all were given authorship in the paper! Without any objective criteria, based on my CV the scientists believed that since I have no good reco, no publication so I must be unsuitable.
    Now, come to another scenario. I applied for a postdoc fellowship at my own country India. I had not money. I borrowed money from one of my friends, took train ticket went for the Interview. In the interview committee, they asked me and told me, "you should apply abroad as you are from a big institute". In the interview committee, there was a scientist from my own institute and another scientist from an adjacent institute. Before talking actually about the proposed work………they decided that I should have not applied. I told him, my PhD was not good, I want to do some work get a publication learn some more things and then apply abroad. They said "since you are from that institute, I am sure you are more capable than any other university student".
    They didnt give me that fellowship just because I had proposed to work in a small lab in India.
    Now, thats about the system.

    When I was writing thesis, my guide tortured me like this. She said give the reference. Now the sentence is DNA is a genetic material. Should I give the reference? For everything she was asking me to provide the reference. Now you tell me , it is feasible to give a reference for each and every thing? In your own video you have told that this is not feasible.

    Now come back to spinach and other such things.
    When I say that same thing to one of my "friends" who is a scientist at "University at Iowa", he makes fun of me. And says "thats why you didnt get postdoc"!
    Thats how society works.
    If you are Pauling and say something that is wrong, people will not object.
    If you are like me and say something then people will object, ask for references and even if you are correct but against their popular notion, then they will make fun of you and hate you.
    My guide used to go to temple.
    I asked her, I want to first sequence the plasmid that we have borrowed from the other lab. She didn't allow me. I asked the map, she said that the scientist will get angry from whom that plasmid we have borrowed. I went to 1989 original publication on the net, the map was not there (because it must be in some previous publication what was unavailable), I again told to my guide, then she asked the scientist who send a map, but with limited information. The plasmid has CMV promoter, but minimal CMV. Now how to sequence? It asked my guide that probably we should ask a primer sequence from the scientist from you have borrowed the plasmid. But she refused. She didnt order primer, and multiple times stopped me and discourage me for getting that plasmid sequenced. Then I asked her, I would do a transient tranfection first to check if this plasmid is working. But she against refused, saying that you are wasting money, Just use that plasmid for "stable transfection"…………
    And so on……….
    Big big scientist,……going to temple…………..want a person with "Faith"…………………………………
    And they are being paid from the public money.

  • Can you make a video about whether the mond landing was fake?

  • I was taught in A&P (anatomy and physiology) that our microbes outnumber our cells by 10 – 1! How could community college mislead me??? 😱

  • But, we were taught that the microbes in AND on our body is ten to one. What would the ratio be if you include the microbes on us?

  • Well I have a cold right now and I was getting better after drinking orange juice now THERE GOES MY PLACEBO.. THANKS A LOT!

  • awesome, now do "97% of scientists agree, the science is settled". Or is that too edgy?

  • As a teacher I find the 'sugar doesn't make kids hyper' thing a little hard to believe. Although I do wonder if it is maybe the conditions under which my students get sugar that affect them more than the sugar itself. Now I want to try giving them sugar-free cupcakes for the next holiday party and see if it is different or if it is the atmosphere that accompanies 'sugar worthy' situations that is to blame.

  • The microbe shirt could say "half human"

  • My bad science knowledge story…
    High school chemistry teacher in 1980 told me that glass was a liquid with extremely high viscosity. I was blown away when, 30 or so years later, I found out it was wrong.

  • damn't I'm in the middle of of chugging Vitamin C because I have a cold right now…

  • The earliest source for the existence of atoms is Democritus.

  • Water freezes at 0 c at a sea level.*

  • Wouldn't you lose more body heat from your head because heat rises?

    Then again, I've never been 100% convinced that heat rises. Can anyone give me a reliable source for that information?

  • There was and there always will be, these scenarios coming up our face.

  • We are all smart…….or not. To be, or to not be…..

  • Don't forget about libraries! A great place to get access to accurate information.

  • 1. Iron in spinach
    2. Colds and vitamin C
    3. Losing heat through your head
    4. 8 glasses of water a day
    5. Sugar and hyperactivity
    6. 10 to 1 microbes
    7. ??? I want my money back!

  • Our blood isn't blue.

  • I agree about Wikipedia and I've said it for years, it's an amazing source for tons of citations if you're writing a paper.

  • Sugar does effect small children. I have experience, and I wish it was not true. It would be nice to give my grandkids a treat without an ampage within 10 min. They arent comfortable in their own skin when that wild energy comes on and I dont want to do that to my favorite persons… But Ive just found this channel today, really enjoying it. Thanks!

  • We need to make a monument to Aaron Swartz for socialize "privatized" knowledge. I co wrote 2 papers back in the day and I can´t acces them without pay.

  • ❤️❤️

  • Did you know …. that your own lymphatic system calls in for help microbes that live in our guts, it order to help with the cleaning of the body, when there is a cellular waste built-up? The microbes are there to digest those toxic enzymes that would otherwise make us sick. Although in eating those wastes the bacteria itself becomes toxic, but thats okay because it will not sustain itself once "its fav. food" (waste) is gone.

  • 8 glasses? I drink more than 20 a day (in 24 hours)

  • That absolutely makes an awesome shirt that I would throw money at to own.

  • The portal reference made my day 🙂

  • This was a refreshingly upfront and honest post, and that's not very common. Thanks for keepin it real.

  • Samurai …


  • Why isn’t youtube promoting the content I’m subscribed to?

  • Pussie

  • I think that there is one thing people tend to forget concerning the combo children and sugar.
    Sugar does not create hyperactivity in kids, but sugar is a fuel, a very fast energy giver (think Dextro Energy)!
    So if your kids are starting to get tired from playing and running around and you give them something sugary, chances are they are getting a nice little energy boost out of it and after a few minutes start running around again.
    I think the contrast between the tired kid and the 'refuelled' one is what people tend to see as hyperactivity because the kid was gradually getting tired and all of a sudden seems to be full of energy again.

    On a side note, most foods will give energy of cause, but sugars just metabolize a lot quicker.

  • 11:32 "if you want common knowledge to be true ,you have to let true knowledge be common."

    totally agree

  • Okay Adam Ruins Everything 😆

  • what if all the sand in the sahara was replaced with water?

  • Like that the "fact" that salt is really bad for you. It's based on animal research where the animals where given extremely excessive amounts.

    Of course, that is no excuse to suddenly add all the salt to your food. Just that the barrier of "too much" is way higher than what common knowledge prescribes.

  • "If you want common shirt to be good, you need to let good shirt be common"
    – Me (now)

    This is a formal recommendation for adjustments to the citation, presuming assuming common taste being not shite is faulty. Thank you.

  • I know the vitamin c study but every time I get a cold and I take vitamin c – the sore throat goes away and the cold doesn’t take long to go away. It’s doing something. I don’t think it prevents or cures but it does seem to do a good job with support

  • He is not lying about the paywall – I don’t know how many times I just want to learn something and it cost $7 just to rent the article for 48 hours. It’s so frustrating. It’s not even affordable to read the knowledge

  • wow kinda surprised that vaccines causing autism hoax started by andrew wakefield wasn't listed here.

  • If the presenter is honest and knowledgeable, in a couple of years he will have to do a debunking video of this video, because I heard a couple of "urban legends" also here.

  • This needs to be your class that's taught in schools every year. In the informationage we live in it's more important than ever

  • yeah i know you're guilty of it too. it's why i unsubscribed.

  • No wonder why i never drink water and im still fine!


  • wait, vitamin c makes an environment in that immune cells can develop better, it wouldn't kill the virus, but help your immune system to develop cells for either hunt the virus or prevent bacteria from making an infection when the immune system is busy with the virus.

  • Why do you use cereal as an iron content comparison? Cereals have added iron and it's not biologically available iron, is it?

  • my parents thought sugar caused me to behave badly and I know someone else who won't let her daughter have sugar for the same reason

  • pretty sure Dr Luckey wasn't alive in the 1860s, when the samurai were abolished

  • 1:17 Huh? I thought 0ºC was the temperature where ice start to thaw.

  • My first time using Patreon… it had to be this page💖

  • poops. I've never taken one. I leave them.

  • 32 degrees Fahrenheit

  • Wow wow wow, saying that published peer reviewed science isn't really available to the "general public" is very much exagerated to my opinion. Just email the corresponding author and they'll happily give you a copy of their paper ! No need to go through the very flawed paywall system of the journals.

    P.S. : plus saying that peer-reviewed articles aren't available would make a point to which creationists and other groups of uneducated people could hold and use to attack known facts and use them against scientists, which would be unacceptable.

    P.S. 2 (not the video game console lol): if you wanna avoid the term "general public" btw, I'd say "non-academia public" it's a bit pompous but it doesn't patronize them 😀.

  • LOVED the cake reference!

  • How about this for a t-shirt. Your body is half poop making cells!

  • Wow this guy is like really arrogant and obsessed with himself ×wⁿ

  • We are the General Public. Salute us! But don't go to us for your scientific truth, yeah?

  • Well Joe, It's Okay To Be Wrong sometimes


  • So it was faith all along regarding the orange juice for preventing getting sick? Oh man! I'd wish I hadn't watched this :'(

  • Thank God for Alexandra Elbakyan

  • The vitamin C and protein story is just for cell repair and growth, you know, producing white blood cells. So that Vitamin C story has merit, just not the killer of bacteria.

  • OK, that Rocky clip was amazing.

  • The "tongue map" is another example of scientific myth widely taught as fact.

  • So in other words, we're mainly microbes.

  • Great video! You should also make a video debunking the "97% of climate scientists agree" urban legend and Michael Mann's "hockey stick". Oh, and eat your spinach with bell pepper or other sources high in vitamin c. It will make the iron absorb better.

  • A method I use when studying or working on college projects is to start by going to Wikipedia and exploring the papers it cites. It is a good source of papers for you to start with as the search for them can be difficult at first.

  • Dude! Please make yourself an "I'm on par with microbes" shirt to set the record straight. It would be so meta.

  • It's Okay To Be Wrong
    unless you point it out later on

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