Does your poop float? Does it sink? Do you have floaters and sinkers depending on the day?
Maybe you're one of those people that never looks to see.
Nah, don't lie. You look.
So if you have looked, surely you've wondered...what makes poop FLOAT? I seem to recall asking my mother this once as a kid and she told me it was fiber and that fiber floats. Since I have now found out that, chemically, that's a dirty lie (she didn't know, so it wasn't intentional, and she always has promoted a high fiber diet), I continued to wonder...why does some poop float while other poop sinks?
The answer, my friend, is blowing in the wind. As it were.
(Source. You know that you will now be looking at and rating all your poop. It's unavoidable.)
Levitt and Duane. "Floating Stools - Flautus vs Fat" New England Journal of Medicine, 1973.
The possibilities for floating poop are pretty limited. If poop floats, it must have something in it that is less dense than water, right? And what do we have in us to poop out that's less dense than water?
Well, we have FAT. And until this paper came out, it was widely assumed that people who pooped floaties had fatty feces. This is actually a medical condition called steatorrhea (word of the day! Work it into a sentence with your coworkers. Go on, I dare you). It's not harmful really, but lots of fat in your turds can indicate things like a lack of acids in your bile. So it seemed odd to these authors that, even though a lack of acid in the bile is pretty rare...about 10-15% of the population regularly had floaties (I would really love to know where they did the survey for this number "Hi, is this a good time to call? We are conducting a brief survey of your s**t, it should only take a few minutes of your time...").
So is it really fat causing all the floating? Well, clearly you need to do science. So the authors of this study got 9 people whose poop floated, 24 whose poop sank, and 6 people who definitely did have steatorrhea. They pooped.
Then the intrepid investigators (and they must have been intrepid for this one), had to TEST the poop to see if it REALLY floated, so they took a piece of each person's poop and put it in some water and checked (you'd think they could just have checked the toilet bowl, but no). Then, they assessed the density of the dung, with classically scientific methods.
The piece of poo was assessed for density, and the rest was analyzed for fat content.
And then they analyzed for GAS. And in the methods, the real reason for the study came out.
I love that. The true measure of a scientist. "Hey, my poop floats! That's weird, I wonder why? Well. I DO fart a lot..."
And it turns out, the investigator had it right. Poop that floats isn't fatty...it's GASSY.
(Figure 1 from the paper)
Here you can see the specific gravity (a measure of density) of the poo from the various groups. The floaters are on the left, the sinkers are in the middle, and the fatty feces people are on the right. You can see that the density of the floaters and the fatties is much lower than that of the sinkers...until you remove all the GAS. When you remove the gas, the floaters achieve a density that matches the sinkers, while the fatties are still low. So we know that for people with steatorrhea, the fat is what changes their density, but for the 10-15% of the healthy population with floaters? It's all about gas.
And so, in a way, my mom was actually right. Fiber probably CAN make for floaters, especially if the fiber produces more gas. So the next time your poop floats, or sinks, take comfort. It's not fatty feces, it's just some gassy guano.