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Why some feces float and others sink (phys.org)
169 points by pseudolus on Nov 21, 2022 | hide | past | favorite | 113 comments


Thankfully in the pre cellphone era, I was on a canoe trip in Algonquin Park. In the middle of a large Lake, the call of nature struck with a sense of urgency that required a solution quicker than just, "Paddle harder to land."

A jump into the lake and removing of trousers resulted in an "Aqua Dump". But alas it was a floater, rather than sinking to the unknown depths. It was a shocking discovery at the time.


Just wonder, what would you have done if you had a cellphone?


Perhaps they were not alone, and today someone would have documented the result?


Yeah, now they wouldn't need to tell the story, they could just link the YouTube video.


Took a video of my camp councillor trying to swim away from a floating turd and gone viral on TikTok.



This has igNobel written all over itself.


Asking the big questions here!!

What I really want to know is what happens to "ghost feces"... Sometimes you know one dropped into the toilet but it is nowhere to be seen...


Typically that's very heavy feces with no gas caused by various bacteria in it, and it slips right down the plumbing without needing to flush.


Yep, if you want to experiment, take a dry toilet (no water) and roll marbles until you get it just right to "halfpipe" its way out the drain.

Water affects this but not much; or you get a rocket-floater that dives down and comes up on the "other side" of the built-in trap.


Rocket floater!


ninja poops


I call them dolphins


If you want to avoid it, get a german toilet[1]. Depending on your opinion on stool inspection, it’s either the best thing ever or the opposite.

[1] https://www.google.com/search?q=german+toilet



Butt vee donn't häff zem anymore! All 'Tiefspüler' nowadays. Can't remember having seen/used the last old one. Has to be 20 Years+, or more like 30.



At school, I was taught that floating poop was a sign you have enough fiber in your diet.

A quick Google suggests that digesting fiber changes the gas/air content.


notice this on keto, many more sinkers with fat/protein heavy poo I guess?


"what's your poo telling you" is one of my favorite white elephant gifts. Gave it to a family member when they were in college, they kept it in the bathroom and it was stolen almost every time they had a party.

https://www.amazon.com/dp/0811857824/


So far the discussion in this thread is lacking, some would say its shit.

Understanding our gut is an overlooked part of medicine and biology. I think theres a certain taboo around the subject. But you can learn a lot about health, your mood, sleep cycles, etc from what comes out the other end. We need more research in this area.

A decade or two ago, fecal transplants were considered joke medicine. Now its an important tool in treating certain gut infections: https://en.wikipedia.org/wiki/Fecal_microbiota_transplant


> But you can learn a lot about health, your mood, sleep cycles, etc from what comes out the other end.

Was talking about that with my GP. His view was that there's a lot of variance on that front, and that we shouldn't read too much into it. In particular, it's not because your shit isn't "perfect" that you're unhealthy, and there's not much to do about it anyway.

Don't shoot the messenger! I know this is HN where people want (and think they can) optimise everything,


Definitely check your stool often and for things like mucus and blood. It could be a warning sign of something more sinister, and if you do find anything questionable contact your GP and get it checked out.

On a lighter note, this paper is _really_ studying the gut flora which we do know has at least some impact on immunological function.


Žižek on toilets:

https://www.youtube.com/watch?v=rzXPyCY7jbs

>The German toilets, the old type -- now they are disappearing but you still find them -- it's the opposite. The hole is in front. So that when you produce excrement, they are displayed in the back, they don't disappear in water. This is the German ritual, you know, use it every morning, sniff, inspect your shits for traces of illness. It's High Hermeneutic. I think the original meaning of Hermeneutic for Germans may be this.

Žižek: Ideology and Toilets:

https://www.youtube.com/watch?v=bpSiMbkhkuE

>"It is easy for an academic at a round table to claim that we live in a post-ideological universe, but the moment he visits the lavatory after the heated discussion, he is again knee-deep in ideology."

https://en.wikipedia.org/wiki/Hermeneutics

>Hermeneutics (/ˌhɜːrməˈnjuːtɪks/)[1] is the theory and methodology of interpretation, especially the interpretation of biblical texts, wisdom literature, and philosophical texts. Hermeneutics is more than interpretive principles or methods we resort to when immediate comprehension fails. Rather, hermeneutics is the art of understanding and of making oneself understood.


>So that when you produce excrement, they are displayed in the back, they don't disappear in water.

We called this the "shit shelf". And it had the unfortunate side effect of exposing the smell, so you got used to flushing during and not just after.


Most people probably need to flush during to keep the toilet from clogging. Not everyone has the luxury of an aircraft lavatory.


Was the original goal to prevent backsplash?


"In some aristocratic households, the Herzog or Fürst would appoint a physician whose sole duty was to inspect the stools of the family members daily, making detailed notes on consistency, form and appearance. He would recommend adjustments to the nobile diet accordingly. The specially shaped receptacles for the material to be inspected thus became intricately associated with nobility and wealth, and during the rapid industrialisation of the late 19th Century, middle class urban households adopted them in vast numbers"

From the History of European Stool Inspections, Henry O.R. Scrap (Oxford 2003)


>History of European Stool Inspections, Henry O.R. Scrap

Nominal determinism.


Busted!


I think the original goal of having a shit shelf was so that you had something to talk about for the rest of the day.


No. It was to facilitate detecting parasites.


It was a work-around to avoid patents on toilets.


> Definitely check your stool often and for things like mucus and blood.

Here in Italy we are checked every two years at +50yo: huge lines of people dropping off their small amounts of (safely stored in an appropriate container) poo. A few weeks later...good news, or bad, in the post. Both my wife and I were a bit embarrassed at first, being relative youngsters, but the over 70s - a great day out for them.


What would mucus even look like in a turd?


Same as it looks coming out of your nose or throat - clear to whitish/yellowish.


Your gut literally has a brain in it with as many neurotransmitters as the actual brain. The phrase "gut feeling" is literal, your gut can actually control you.


> Was talking about that with my GP. His view was that there's a lot of variance on that front, and that we shouldn't read too much into it. In particular, it's not because your shit isn't "perfect" that you're unhealthy, and there's not much to do about it anyway.

I figure this is why the parent post is recommending more research into the area. Your GP is probably right that you shouldn't look and draw conclusions, but I'm curious as to whether it's because conclusions can't be drawn, or because we simply haven't learned how to draw the right conclusions yet.


> In particular, it's not because your shit isn't "perfect" that you're unhealthy

"Not perfect" for means "meh" (sometimes too solid, sometimes too liquid, sometimes with weird things inside, ...). If I had systematically a weird poo I would be worried.

At the same time: it is not because your poo is "perfect" that everything is fine. Some things you cannot see, some other are not there but somewhere else (even related to colon, stomach, ...)


I can't optimize my way out of a wet paper bag.


Strong agree. For all the evidence and talk about 'the microbiome is a newly discovered organ', people sure do struggle to look beyond the surface reading of the research-- yes, all the research in this area is research about shit, and often involves putting things inside arseholes. Hilarious as arseholes undoubtedly are, its a real shame seeing this research held back by this.

One interesting corollary of the article-- I wonder if human corpses sink or swim in accordance with their former flatulence-- and how much the old tale about eating after dinner is determined by these selfsame gasses!


Historically John Harvey Kellogg was obsessed with digestion and intestinal flora[1]. The FOBT, used in diagnosing colon cancer has been around since at least the 1960s[2].

[1] https://en.wikipedia.org/wiki/John_Harvey_Kellogg#Battle_Cre...

[2] https://en.wikipedia.org/wiki/Fecal_occult_blood


That reminds me.

There was an old movie from the 1990s about Kellogg: https://www.battlecreekenquirer.com/story/entertainment/2019...


I totally forgot about that, it's actually really good.


The original guaiac FOBT is a crude screening tool for colon cancer and never used for diagnosis in the strict meaning of the term (it’s somewhat sensitive and not at all specific).

It’s also confused these days with the more sensitive and specific FIT test. FOBT has no relevance in modern medicine.


Yeah, we’ll aware. I was pointing out the history of medical science being interested in the topic that OP claimed they were ignoring.


And circumcision...


He was only sort of a proponent of that in extreme cases. People get hung up on the sex stuff, but he was way more into digestion.


I'm not familiar with the literature but I was rewatching Scrubs recently which is a 10-20 y/o show and it was mentioned in an episode that you could tell a lot about a person's health by looking at their stool, even made a joke about a "Doctor Toilet", a smart toilet that analyzes your stool


In the musical episode they have a song called everything comes down to poo.

https://youtu.be/2BDd0XseGtU


First thing I thought of when reading this study.


I have coeliac (celiac) disease, ingestion of various cereal proteins (in wheat, barley, rye; thankfully not oats for me) cause an exciting array of gastrointestinal phenomena.

A visual inspection is usually enough to tell me about low-level contamination.

Recurring or high level ingestion becomes fairly evident to anyone within earshot, and effects usually last more than a week :/


The gut-brain axis (GBA) consists of bidirectional communication between the central and the enteric nervous system, linking emotional and cognitive centers of the brain with peripheral intestinal functions. Recent advances in research have described the importance of gut microbiota in influencing these interactions. This interaction between microbiota and GBA appears to be bidirectional, namely through signaling from gut-microbiota to brain and from brain to gut-microbiota by means of neural, endocrine, immune, and humoral links. In this review we summarize the available evidence supporting the existence of these interactions, as well as the possible pathophysiological mechanisms involved.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4367209/


The other day someone shared a paper linking some gut bacteria to oxytocin levels, which regulate sociality.


What a time to be alive.


I see someone else is looking forward to Károly Zsolnai-Fehér's presentation of this exciting research.


I think it would be a good idea if they made an app with more info.

And maybe fecesbook would be a good name for such app.


Social media is already a pretty shitty situation, this would fall right into place. =)


Since I've stopped eating bread I only have sinkers. No more floaters, no more stinking toilet, no more multiple flushes.

I still don't know exactly what caused it, if it was the gluten or the modern issue that industrial bread (even whole grain) isn't given enough time to rest (long-term fermentation?) so that it then continues to work inside the gut causing the problems, given a certain unhealthy gut microbiome which either can't deal with it or somehow goes crazy on it.

It was not just bread, though. Also oatmeal and cereals, so it isn't that clear.

It was always related to the amount of gas which would end up in the feces.


Phys.org might want to reread european cookie notice legislature, just linking to "about cookies" when clicking "cookie options" with no direct way to reject doesnt fly anymore.


Can these be reported somewhere?


I smell an IgNobel in the authors' future. Given the subject matter, that's not all I smell.

And gut bacteria are involved, so this is super relevant to Hackernews.


The article didn't answer the one question I had. Which is more indicative of a healthier gut biome - a floater or a sinker?


It's likely that a sinker is indicative of healthy stool. The actual article notes that floating stool is correlated to increased presence of B. ovatus which is "an anaerobic commensal bacteria linked with flatulence and intestinal bowel diseases" [1].

[1] https://www.nature.com/articles/s41598-022-22626-x


A stinker. No seriously my wife and I were just talking about this a few days ago. The floaters indicate you're not processing fats very well. So the sinkers.


But the article says that floating vs non-floating has little to do with fat content. It's the gases generated by bacteria that cause the stool to float, not the fat.


> The floaters indicate you're not processing fats very well.

No. As a cited article concludes: "Thus, stools float because of an increased content of gas or water (or both); the floating stool should not be considered a sign of [excess fat in feces]." [1].

[1] https://www.nejm.org/doi/full/10.1056/NEJM197205042861804


They are all stinkers.


They reject your argument in the article, just into the 2nd paragraph.

> Prior to the 1970s, scientists believed that fecal matter either sank or floated depending on the amount of fat it contained. Experiments showed that not to be the case.


Not sure of the healthier gut biome, but that of health, it's the sinker


Queue the next Elizabeth Holmes to get into this in a revolutionary world beating way.


I nominate this paper for an Ig Nobel.

https://en.wikipedia.org/wiki/Ig_Nobel_Prize


I for one am glad we are finally investigating the real issues of society


Is this related to the reason some stinks and others don't?


I should not have read Hackernews while having dinner...


TL;DR - poop is alive!

Maybe it's because I've gone through various hobbies related to fermentation but trapped gas seems like the most obvious and likely answer. Especially when you see bubbles around floaters. It's also very simple to test...take a floater, put it in a vacuum just above where water will start to boil off, then see if it still floats. Alternatively, compare its displacement before and after smooshing it through a fine grate. (Note I said simple, not easy xD)


In space they are all floaters.


As the astronauts of Apollo 10 found out


and nobody can hear you scream


Or poop


I look forward to the day when I can buy probiotics specifically to make my poop sink or float.


This is IgNobel right away


When I walk in to a public men’s bathroom I hear a lot of noises I don’t hear in my own house, I often wonder what’s going on with other peoples bodies given I only know my own experience, clearly we’re all very different ;-)


I also wonder in what state some leave their own toilets at home after they have done their business.

I was also puzzled by those diagrams showing how you are supposed to sit on a western toilet seat. But then I watched some bits of one of those crual japanese tv show where their collapsed all the walls of some public toilets when a poor guy was at it (I hope it was an act). To my own surprise the japanese are sitting facing the flusher/wall, not facing the door. Plus you have countries where squat toilets are the norm.

Sex is another area where there are few social norms since you never learn by imitating peers (other than porn which is a terrible model).


Of course you're supposed to sit how the Japanese guy sits. The top of the bowl is there so you can rest your book in it. Butters knows.


Butters knows

You won the internet today, sir.


>To my own surprise the japanese are sitting facing the flusher/wall, not facing the door.

Yeah no, that is not a "Japanese" thing. I have no idea what show you were watching but it was probably just a gag, or a way to avoid having to show his genitals, or something that one person did for whatever reason.

There are some people who sit that way. For example, British comedian Bob Mortimer said on an episode of Taskmaster that he does it because his anus is unusually high.


How would an unusually high anus benefit from facing away from the flusher / wall? I can only envision it being more likely to end up with the "mud" landing outside of the bowl.

Is it to avoid "mud" ejecting into / against the toilet seat?


https://www.youtube.com/watch?v=zdll1Ie4AW8#t=7m5s (07:05 if it doesn't seek automatically)


Oh god.. poor guy.

Thanks for the link and timestamp info!


That's how you're supposed to use a traditional Japanese toilet, facing the flush.

Now granted, traditional Japanese toilets are getting rare in Japan, it's mostly western style toilets now.


"Public restroom shyness"? Some people are so uncomfortable going bout their business in public that they have trouble getting things moving. I used to work with a guy who would leave work for the day if he had to take a dump as he would only shit at home which was an hour commute one way.


Back when I was commuting to an office, my favorite thing to learn about a building was where the least-used bathroom was. I would make my daily paid-to-poop pilgrimage to this sanctuary.

It was a slow and spiritual journey, like walking on knees to the Basilica of Guadalupe.


I was quite uncomfortable (but managed to get the business done) for the first week or so after arriving in the US (business trip) due to the inch-wide gaps around stall doors. When flying back, going to the toilet in the first European airport was very... moving.


I contracted for a company in the US (I'm in the UK usually) and the stalls were terrible. Big gaps between the doors and frames, and really big gaps underneath the dividing walls too, so you could identify your co-worker by their shoes. The ability to put a noise to a face was really quite off-putting.


Be assured, no one is spying on you or cares that you are pooping.


That wasn't what I said.


Come to Scandinavia. We are blessed with almost no “stall” type restrooms. Wherever there’s multiple toilets, they’re each in a separate proper tiny room.

The exceptions seem to mostly be older fast food places and roadside taverns.


Just a quick thing I discovered for people experiencing this when they are in a stall.

Plug your ears.

I don’t know exactly why it works but for me it’s magical in its ability to get things moving.

If you have stage fright while at the urinal, start going tricky math problems in your head.


Are you from the US? US public bathrooms are especially bad for privacy, because they only have thin wooden walls that start about 15 inches above the floor (so that anyone passing by can see if someone is laying on the floor, passed out).

In my country, where drug use is not such a big problem, bathrooms have actual brick walls, giving a person inside much more privacy.


For the record I am not one of these people. I did, however, discover after 40-some years on this planet that I am intolerant of soy. I removed it from my diet and I feel so much better, although I am constantly disappointed that it has infiltrated so much food.


Sampling bias. People that have something going on would be spending more time in the bathroom.


I think it's evidence that many people have very bad diets.


tl;DR!: Fat content.


Actually, from the article:

> Experiments showed that not to be the case. Instead, trials with healthy human subjects showed that the difference was due to the amount of gas in a given fecal sample.


A book I read as a child (ca. 1990) claimed it was gas content; good to know it was correct (even if by accident).


Who would have said that it was all the Archimedes Principle.


I’m impressed that you read the whole thing. I came away with fat content, as gas permeates away.


The article is pretty short and it mainly says that it is due gas content. The amount of gas seems to be dependent on the presence of certain gut bacteria.

According to the study, naturally about half of the population of mice produce floaters. When you collect stool samples of that half and inject it on the other half, they also start producing floaters. On the other hand, when you sterelize the gut of the floater group, they start producing feces that sink.

Fat content seems not to be related.


nope, it's fart content


There needs to be another "fart content" dimension to the Bristol Stool Scale.

https://en.wikipedia.org/wiki/Bristol_stool_scale


Oh, boy, Yancy. You reek, ah!


I feel this study is incomplete - we should ask Austin Powers and Fat Bastard to weigh in as well.




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