What's the straight dope on diarrhea?

Does diarrhea help you to get rid of the bacteria or whatever is in your guts that shouldn’t be? Or is it just a symptom with no function?

Where are the bad microorganisms: in the food in your guts, or in the tissue of the guts?

How do you get “tough guts” ie ability to eat dirty food without getting diarrhea, is it like other immunity, ie having the right antibodies?

I don’t have answers to your questions, but it’s worth noting that the bad smell of the byproducts involved is caused totally or chiefly by bacteria, which are in the water that all human solid waste contains. Diarrhea is more smelly because there are more bacteria (IIRC), but that could be a function of (a) an actual increase of bacteria that needs to be gotten rid of, (b) an increase in water in the stool, or © some combination of the above. It’s been a while since I’ve looked this stuff up, but there’s my two shekelim.

Most of human feces is bacteria. Billions upon billions of tiny bacteria corpses. No, wait, they don’t all have to be dead. Billions of bacteria make up your shit. Diarrheal or not.

When I am torturing medical students around the open body (substitutes for campfire) I like to ask them, “Tell me in simple words that any layman could understand what the small bowel is for, then the large bowel.” After they struggle through arcane and complex answers I tell them what I was looking for. (This Socratic method of teaching in medicine is known as “pimping”, by the way.) The small bowel absorbs the calories out of your food. Every single calorie you are ever going to absorb. All the protein, fat, carbs, minerals, vitamins (except one). All the essential nutrients. Everything out of a GNC bottle that’s actually going to be of some use to you comes in through the small bowel.

Then what is the large bowel there for? It dries the shit.

No kidding. When the chyme (digested food byproducts, but not yet shit - generally odorless, or has a faint smell of food) exits the terminal ileum and enters the cecum, it is a continuous stream of slightly pasty fluid. I tell the students, “If you need an operation that gives you a colostomy, that is, you have to ‘wear the bag’, and if you are unlucky enough to need it in your right lower quadrant” (putting my hand on the spot), "you have to keep the bag on 24 hours a day. You have to use special sticky sealants to be sure the bag is attached and not becoming detached by the icky stuff flowing out. You have a bag of liquidy stuff hanging off you all the time.

“On the other hand, if you need a colostomy in the usual place, over here” (hand on the left loewr quadrant), “then you can put the bag on in the morning after coffee, expel your turds, take it off, shower, put on your shirt, and go to work. You can make love with your spouse without it on. You can put it on when you need to take a dump.”

This is only true if you aren’t having diarrhea.

Diarrhea is not a symptom which is of use to the body - in fact, it’s highly dangerous if it gets bad. Cholera is essentially an attack of diarrhea (plus vomiting) so bad it kills you in a day or two. Diarrhea kills children in the third world because it dehydrates them and robs them of electrolytes like potassium that are lost with the watery feces; that’s why a simple rehydrating solution saves so many lives.

Diarrhea means that the function of your colon, which is to dry the shit, is being interrupted. Bacteria (almost always; rarely viruses; occasionally amoebas or other parasites) are making your colon sick, and it’s unable to dry the shit. In some cases (like the vibrio of cholera, which makes a toxin which directly affects colonic mucosa cells), the colon turns around and actually pours water out, stealing it from your bloodstream via the capillaries in its wall.

Now if you take a microscope down to the colonic mucosa, better still if you take a scientist down with you, you will see that “It dries the shit” means a thousand ingenious and tiny little operations involving miniature potassium and sodium transporters in the membranes of the cells, to suck out these electrolytes and let water diffuse passively after them. Billions of bacteria hang out against these mucosal cells, sometimes helping them actively (E. coli makes vitamin K which we can reabsorb - the only vitamin not absorbed in the small bowel), sometimes helping them passively (great volumes of E. coli may block more dangerous bacteria like shigella and salmonella from reaching the mucosa), sometimes harming them actively (E. coli O157:H7, in uncooked hamburger meat, has killed people’s children). All these things are involved in a huge production line, or dance if you prefer, which ends us up with neat little turds instead of a continuous stream of pasty shit. And any large and complex production line can go wrong. Think of ordinary diarrhea as workers throwing their wooden shoes into the machinery they resent, and cholera diarrhea from a vibriotoxin as terrorists taking down the factory with sarin gas. If the factory recovers, the water extraction process begins again, the water goes back into the venous capillaries that drain your gut, and you end up with neat little turds again.

A final remark. Why do we have this large system to dry the shit? After all, it’s expensive to the body in terms of blood supply, nutrients required, constant maintenance (colonic mucosa cells die and are replaced faster than any other cell in the body), and the presence of a huge reservoir of internal bacteria that can be remarkably dangerous to us.

My answer to this question comes from no Cite but makes a little sense. The only large animals in Nature that have continuous pasty dribbles of shit are fish and birds. These animals are hard for large predators to track by the dribble of shit. Let’s you and me start on the savannah at five million years ago. You have no colon, and I’ll have a colon. There’s a sabertooth cat on our trail. Which of us do you think it’ll pick off first?

Sheesh, nine hundred words and I fail to answer two questions in the OP.

The bad microorganisms always start in the food in your guts, where some of them can harm you without even getting into your mucosal wall (by secreting toxins that hurt you). But if you are very unlucky, bad bacteria or amoebas can penetrate into the colonic mucosa cells, or past the mucosa into the wall of the colon itself.

The colonic mucosa cells desquamate (fall off) so very often, partly to keep the bacteria from getting any further. (It’s sort of kamikaze, now that I think about it. Protect the submucosa! Banzaiiii into the shit stream!) The lamina propria, or the layer of wall around the mucosal crypts (the mucosa is infolded a great deal to give it more surface area), is stuffed with white cells that are there to fight the bacteria. More collections of white cells are staffed along the muscularis mucosae at intervals; they look like small fortresses to me, ready to recruit more soldiers should there be a full-scale bacterial invasion. Outside the muscle wall, the veins that take blood away from the colon run through a layer of tissue called the mesentery that has huge numbers of lymph nodes in it.

But people still die now and then when significant numbers of bacteria make it through all these defenses and get into the blood. That’s called “sepsis” due to “translocation of bacteria across the gut wall” and its old name is “blood poisoning”. Often leads to death. In the absence of antibiotics, always led to death.

How do you get “tough guts”? I have no idea. Dopers?

By the way, I don’t think this is necessarily a very beautifully designed or optimized system. It has the feel of a whole lot of kludges to me. Inherited kludges, one building on the previous one.

But that’s the wonder of evolution.
Co-evolution - since at least E coli came there with us, evolving all the time.

Your explanations were epic and engaging. Thanks for answering questions I didn’t know I had!

“Epic and engaging” - I love it.
Thanks for making my day.

I like the ads at the bottom of the page. “Save on Aerobic Bacteria”. “Dog Diarrhea Help – help your dog the natural way”. Just saying.

“Drying the shit” is not many miles away from “conserving as much water as possible while protecting the body from disease”. The system may run a little inefficiently, but getting very sick is really hard on the body. The study of nutrition and proper feeding of ICU patients still has its controversies, but very sick people may require an additional 30-40% more calories than normal.

“Tough guts”, the ability to eat at the night market in Beijing, fruit in Fiji and the street food of Mexico City – I’d argue you have to have good antibodies. Maybe half of people (according to travel clinics and drug companies which do have a vested interest) get traveller’s diarrhea if they go to a foreign place and don’t take precautions (peeling fruit, not drinking water, being careful with salads, avoiding street food and uncrowded restaurants). But those who travel a lot know street food and new foods are part of the adventure. You could stay healthy by just eating at popular places that presumably go through ingredients quickly enough to reduce bacterial counts. I think exposure is key, though. I’d argue the longer you stayed in one place, the less sick you’d get – presumably since this helps you make antibodies. I can’t recall getting sick from eating Canadian Tire (street) hot dogs, funnel cake or local carnival crap (cotton candy and pogo dogs); but I sure got the gastro when I went to Beijing, or Goa. (Wise travellers anticipate this and bring their own ciprofloxacin, no worries, unless you’re talking about cholera as per gabriela.

Thanks, gabriela. I am stunned that anyone is capable of making the digestive tract that interesting and comprehensible. Your students are lucky to have you as a teacher.

One question for you, if you have the time: How does the chyme (digested food) turn into massive amounts of bacteria? Does the bacteria in you intestines just eat it and multiply? Thanks!




Slight nitpick about the absorptive capability of the large intestine: the colon and rectum also actively absorb short chain fatty acids (SCFA). SCFA, such as butyric acid, are small organic molecules containing 4 to 10 carbon atoms, and are produced by bacterial fermentation of carbohydrates in the colon. Normal bacterial activity in the colon produces a lot of SCFA; the colonic mucosa may transport more SCFA per day than it does sodium or chloride. The colonic mucosa uses SCFA as a major energy source; they can be broken down in the mitochondria of the colonic cells. The active uptake of SCFA also plays a role in the absorption of water from the colonic lumen.

The SCFA absorbed by the colon probably are almost all ‘burned’ by the colon itself, so absorbed SCFA aren’t really a major energy source for the rest of the body. However, they do appear to be important in maintaining the health of the colonic lining. There are tube feeding formulas supplemented with SCFA that are used in patients who have lost a significant amount of small intestine , and patients so treated seem to adapt faster to the loss of small intestine.

To touch on Renee’s last question; bacteria get into the colon via the food we eat. Most bacteria are destroyed by the environment of the stomach and small intestine, but some will sneak through and make it to the colon. Some of the bacteria you eat are adapted to the environment of the colon- once they hit this promised land, they start to multiply like mad. For food, they use whatever protein, carbohydrates, and fats that haven’t been absorbed in the small intestine. Basically, they can reproduce faster than they are swept out of the colon by peristaltic action. Significant diarrhea will wash out many of the colonic bacteria, and it can take a while for things to get repopulated and ‘back to normal’ from a functional standpoint.

We always take a big bottle of Cipro with us when we travel- taken at the first sign of “wow, what a cramp…”

We Brits like an o in our diarrhoea. (It makes it less sloppy). :slight_smile:

Is there any truth to the old saw that eating yogurt after suffering diarrhea is beneficial since it helps repopulate your colon with “good” bacteria?

I think the title of this thread should have been What’s the bottom line on diarrhea?

Or: What’s the poop on diarrhea?

There’s some truth to it. Lactobacillus bacteria are helpful in many ways, as this Ask. Dr. Sears column lists.

And those with lactose intolerance, which is a whole bunch of people, will likely get fewer symptoms from dairy products when their colon is colonized with these bacteria.

Lactobacillus pills, like Digestive Advantage, are reported anecdotally to be just as beneficial, but I know of no formal studies on them.

Question-I’ve heard that the trend for colonic irrigation is so dangerous partially because of the fact that it flushes all the mucous out of your colon, leaving it unable to fight bacteria-is that true?

I read someone extoling the virtues of enemas because they “flush out the mucous-that’s a sign of toxins in your body”, and then someone else pointed out, no, that’s DANGEROUS if that’s happening.

(People think I’m crazy because I say I’d rather puke than have diarrhea. I’ve had bad diarrhea, and unlike puking, which is over in a few seconds, until you have to go again, sometimes with diarrhea, you’re sitting there for an hour or more, with horrible, killing cramps. )

I’ve recently had to go through several months of dealing with chronic diarrhea. After getting tested for all sorts of stuff by both my regular MD and a gastroenterologist (Lessee, you had a colonoscopy recently, you don’t have giardia, you don’t have parasites, you don’t have celiac sprue …), the gastro guy finally concluded that I might have “bile salt diarrhea” (the regular MD had concluded the catchall “irritable bowel syndrome”) and put me on an old cholesterol med called Cholestyramine, which is a bile sequesterant. It seems to work. What’s more, taking that and extra fiber dropped my cholesterol down far enough that my MD took me OFF the cholesterol / triglyceride med he had been feeding me. It may be possible that the blasted stuff (lopid) was responsible for my diarrhea in the first place, but I’m inclined to simply keep taking the cholestyramine and not pursue the matter.

One thing I’m a bit curious about from my own research - cholestyramine seems to be fairly commonly used following gall bladder removal. Gall stones or a non-functioning gall bladder was not something that the GE discussed, or examined me for, AFAIK. Wouldn’t excess bile getting dumped into the colon be symptomatic of that?

What’s the opinion of OTC loperamide, BTW? My regular MD seemed to think it’s terrible and you should never use it. My point of view was that it seemed to provide relief, so until you figure something ELSE out, doc, I’m gonna take it. The GE didn’t seem to think it was so bad, as long as you weren’t masking the symptoms of an actual serious infection.

Please refer to page 1 of the following:
** FECES. 1. Composition **
This document from University of Wisconsin, Milwaukee, says: feces are 75% water and 25% solids. Of the solids only 20% is bacteria, 30% cellulose, fat 10 - 20%, inorganic 10 -20%, and undigested protiens 10%

Diarrea can be cause by any of a large number of bacteria as well as poor sanitation when preparing foods.
** Eight Bacteria Causing Diarrea **

**“Tough Guts” **are hard to come by. Avoid contaminated foods, practice good sanitation in food preparations, washing all vegetables thoroughly and you may still get a bad case under rare or unusual circumstances. (Montezuma’s Revenge!)

You’re absolutely right, you know, and I wonder why I had a blind spot on this essential point. I’ll make sure to add it when I explain the shit-drying process to the medical students.

You want a neat little pile of turds you can deposit in a hidden place (use the stick to cover that which cometh from thee, as the God of Israel instructed) so that when the sabertooth’s coming after you, you don’t leave a stinkified trail. And you also want to reclaim all that water you otherwise would’ve lost in the poop.