How to stop diarrhea and what NOT to do

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We’ve all wrestled with diarrhea at some point. It’s a shared experience that none of us wants to share. 

But there isn’t just one type of diarrhea. It comes in various shapes and sizes. And being able to read these differences can help us understand what’s going on inside us and how we should treat it. 

In today’s short episode of ZOE Science & Nutrition, Jonathan and Dr. Will ask: What are the health risks associated with diarrhea, and how can we treat it? 

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Mentioned in today’s episode:

  • Diarrhea, a global overview from the World Health Organization (WHO)

  • Key takeaways from a University of Oxford analysis of the global impact of antimicrobial resistance

Episode transcripts are available here.

Is there a nutrition topic you’d like us to explore? Email us at, and we’ll do our best to cover it.


[00:00:00] Jonathan: Hello and welcome to ZOE Shorts, the bite-sized podcast where we discuss one topic around science and nutrition. I'm Jonathan Wolf, and I'm joined by Dr. Will Bulsiewicz. And today's subject is diarrhea.  

[00:00:16] Will: Unfortunately, it's something that all of us have wrestled with at one time or another.  

[00:00:22] Jonathan: And Will, I was going to say how urgent it is that we discussed this topic but actually in all seriousness, when you have diarrhea, it's really not a laughing matter and it's also another one of these topics that I think that is embarrassing and no one ever talks about. So I think ZOE bravely goes where other podcasts fear to.  

[00:00:41] Will: I'm glad we're talking about this Jonathan, diarrhea is incredibly important and it can be a real challenge to decide the best course of action when you're suffering with it. Today, I think we should talk about the health risks associated with diarrhea and its various treatments. I can't resist. Let's not hang around then. Let's get into it. 

[00:01:01] Jonathan: So let's set a scene, um, that I think many of us will have experienced in our lives. So let's say you are having a meal at a restaurant. You've ordered something spicier than you normally eat. At the time that evening, everything seems fine, but the next morning you find yourself stuck on the toilet with these sort of loose, watery stools. 

[00:01:20] Jonathan: What's happening here will,  

[00:01:22] Will: well, I mean, we've all experienced this Jonathan, uh, at one time or another, and, put simply when you, when you have diarrhea, it's because your intestines have been flooded with an abnormal amount of water. There are a couple of ways this could happen. One is that you're not adequately absorbing the water out of your intestines, but the second is that water is actually being pulled into the intestines and therefore there's just too much of it there. 

[00:01:48] Jonathan: So, well this is all sounding a bit like a chemistry experiment. Um, can you help me to understand how that spicy meal I ate, which doesn't feel like it's got a lot of water in it, causes me to have too much water in my intestines?  

[00:02:01] Will: Yeah, that's a good question. So spicy meals actually contain a phytochemical called capsaicin, and this is something that you'll find in chilli peppers. This is what makes the chilli peppers spicy. Capsaicin actually irritates pain receptors that exist within your intestines. So your body basically wants to get it out as quickly as possible. And in this particular case, Jonathan, things start to speed up, and then boom, there's diarrhea. 

[00:02:26] Jonathan: So Will, you know, you say that and I think pain receptors don't sound like anything I want to irritate. So is this capsaicin bad for us?

[00:02:36] Will: I mean like, like so many things in the appropriate amount capsaicin is actually wonderfully good for us. So it's actually used in some medicines. It's been shown to have the ability to numb pain. So if you think about it if you eat a hot pepper after the burn, there's a little bit of a numbing sensation in your mouth. So the interesting thing about that is that this explains why capsaicin can be therapeutically used to treat arthritis pain, and also it's been shown to be beneficial for people that have irritable bowel syndrome or IBS.  

[00:03:06] Jonathan: I've also noticed that sometimes very fatty meals, like really fried foods, which I don't eat all the time, can also upset my bowels. Is that a thing?  

[00:03:17] Will: Yeah, this is a common thing as well, and, and there's an explanation for it. So this extra fat, your body needs more time to break down the fat and pull it apart and get it into the bloodstream. And in this process, the extra fat can actually start to pull water in.  

[00:03:32] Jonathan: So are there any other foods that can trigger sort of diarrhea and these sorts of symptoms? 

[00:03:38] Will: There are some classics. These are ones that many of us have heard of before and in fact we've discussed on this podcast. So some of them include dairy products, specifically non-fermented dairy products, caffeine, sugars, and that includes also artificial sweeteners. So, you know, for example, drinking a large amount of diet Coke could definitely trigger diarrhea for a lot of people. The thing about diarrhea, Jonathan, is if you have just one or two loose bowel movements, that honestly is probably something that you ate.  

[00:04:09] Jonathan: What about if it isn't food? You're saying it might be food, but what if the problem persists? Even if you've maybe adjusted for some particular food you thought might have triggered it yesterday? 

[00:04:18] Will: If you have three bouts of diarrhea within a 24 hour period, that's when I start to really consider the possibility this could be an infection. And the term for this that we use is gastroenteritis, which means infection of the stomach and intestines. You could also call it a stomach flu or a tummy bug. Up to 90% of the water that we consume in our diet, or that's secreted into our intestines, Jonathan, as a part of digestion, ultimately gets absorbed by our small intestines. So our small intestine is where our water is mostly getting absorbed and the small intestine is really long. The colon, which is also called the large intestine, it's large again because of the caliber, the size of it, but not the length. The length is actually far shorter, so typically the colon is about five feet in length, so we're talking about a meter and a half to possibly two meters in length. So the point of this though, Jonathan, is that if hypothetically we have an infection and that infection is affecting our small intestine, Then ultimately all of this water that was supposed to get absorbed in the small intestine is going to get shunted down to the colon, and it's just gonna completely overwhelm the colon. We are not anatomically designed to stop water from com from coming out. We're anatomically designed to stop solid stools from coming out. And so in these particular settings, it can be actually very hard for us when we have that urgency. Even when we're completely healthy, even when we're young and strong, it can still be hard for us to stop it from coming out. 

[00:05:45] Jonathan: So what other signs are there that an infection could be behind this?  

[00:05:49] Will: So in addition to diarrhea, infections often will also include things like nausea, vomiting, um, a loss of appetite. You could start to lose weight, you could become dehydrated in some cases. There may be abdominal pain. You may see blood in your stool or even have a fever. One of the main things that I look for is the presence of nocturnal diarrhea, where basically the person is waking up in the middle of the night with an urgent need to go to the bathroom and evacuate their bowels. This particular thing, Jonathan, is very important because there are many digestive conditions that exist and the majority of them will not wake you up in the middle of the night to have a bowel movement. But if it's an infection or if it's an inflammatory cause of your diarrhea, that's the kind of thing that will get you up.  

[00:06:33] Jonathan: What do you mean by inflammation in this context Will? 

[00:06:39] Will: Well, so inflammation comes from our immune system. So we're talking about inflammatory conditions like inflammatory bowel diseases, ulcerative colitis or Crohn's disease are the classic examples. 

[00:06:50] Jonathan: So those are obviously very serious. So if a person is having this sort of nighttime diarrhea, how can you tell whether this is an infection or actually it's sort of this inflammation from one of these long-term diseases?  

[00:07:01] Will: If it's an infection, it's gonna hit you like boom, all of a sudden. Whereas when it's inflammatory, cause it's something that starts to slowly pick up steam. This can occur in somewhere in the range of like four weeks to anywhere, you know, up to four to six months. So over the course of months, it's like a freight train, like it starts really, really slow, but then it starts to build up speed as opposed to the infection, which is like a rocket taking off within a few hours you feel horrible and you're sick.  

[00:07:31] Jonathan: I certainly experienced food poisoning, as I'm sure many of our listeners have. And I'm just thinking about it right now and I can honestly remember thinking that I felt so bad that maybe dying would be okay at this point. So, you know, not a great feeling. Other than that, like temporary, you know, terrible feeling. What are the risks associated with diarrhea if it's not treated well? 

[00:07:52] Will: We're very fortunate, Jonathan, to live in countries with good medical infrastructure. Cause when we experience this type of explosive, urgent diarrhea, In most cases, this is not going to be life-threatening for people within our type of country. However, in countries with less resources, it actually poses a really significant threat.  

[00:08:10] Jonathan: And we actually did a little research on this and I was really shocked about the results, particularly with children. So in 2019, the World Health Organization said that diarrhea was responsible for the deaths of 370,000 children worldwide, just in that one year, which makes it the second most common cause of death in children under five. 

[00:08:30] Will: That's incredibly disturbing and I hate that. You know, the danger with acute severe diarrhea comes from what your body is losing. Obviously, part of what's coming out are liters of water that you need to replace, and this is easier said than done when a person is simultaneously violently throwing up and they can't keep anything on their stomach. So you can tell from the picture that I'm painting, Jonathan, that it's usually dehydration that lands a person in the hospital.  

[00:08:54] Jonathan: What are the signs of dehydration that would suggest that you are losing too much water? 

[00:08:58] Will: One of the very first things that you will see that I would look for as a medical doctor is that your heart rate starts to increase. 
So you can like literally look at your wearable technology. If you have something, and you would notice this, your body is trying to compensate for having less blood volume, and around this time you're also gonna find that your mouth will become dry. Your lips will become cracked, and if you try to change positions, like for example, going from laying flat to sitting up or from sitting up to standing, you may actually get lightheaded. 
When you do that, these are all signs that you're falling behind on your hydration status, that you need to drink more water, and if you're unable to, then this may ultimately require you to get medical attention so that you can receive IV fluids.  

[00:09:41] Jonathan: So what's the best way for someone to keep themselves hydrated at home? 

[00:09:44] Will: So it's important to acknowledge that it's not just water that you lose when you have diarrhea. There's also a whole load of electrolytes.  

[00:09:50] Jonathan: So I've got a question for you. Will, so I think I know you're supposed to drink these little sachets, right? If you've got, you know, if you've got diarrhea for a long time, you've got really upset the stomach, but I've never actually understood what an electrolyte is. 

[00:10:01] Will: Electrolytes are things like sodium and potassium and magnesium, which by the way, these are the things that we are losing when we have diarrhea. These are the electrodes. And so to replace them, you, you have to have electrolytes in your beverage. And some examples of electrolyte rich beverages that can be really helpful in this situation are things like Pedialyte or in the UK Dioralyte. A broth or a soup because they have electrolytes can also work. And then bananas are interesting because they're a great source of potassium. So if you can tolerate bananas, they can actually be beneficial here.  

[00:10:35] Jonathan: So Will, we've looked at what you could do at home to sort of mitigate the effects of diarrhea, but what about combating the actual diarrhea and just stopping it? Maybe because you need to go out and do things. Is it all right to take Imodium or a sort of another equivalent over the counter drug?  

[00:10:50] Will: Imodium helps to slow our bowel motility, so it can definitely reduce the explosiveness of our diarrhea, which clearly that is desirable in that moment when you're suffering with this issue. But there's concerns that taking the Imodium can actually compromise our colon health. If it's a bacterial infection, it can actually be dangerous in this setting.

[00:11:01] Jonathan: And so why is that?

[00:11:10] Will: So the issue is that our body is having diarrhea because we're trying to actually get rid of the infection. There's an overgrowth of some sort of pathogenic organism. And if you slow down our colon motility, then what you're doing is you're actually trapping that pathogenic organism. You're allowing it to multiply and grow stronger. And this can lead to a condition called toxic megacolon, which I probably don't need to explain in more detail to make it clear that that's not good. 

[00:11:37] Jonathan: I'm already guessing that I don't want a toxic megacolon. 

[00:11:40] Will: Yes. You hear toxic megacolon and you're like, okay, cool. You got me Dr. B., that's enough of that. So, There's something that you could consider instead of Imodium though, Jonathan, and that's Pepto-Bismol, which can actually help to combat the infection and simultaneously help in the setting of diarrhea. It's not as effective at taking the way the urgency as the Imodium is. Either way, you should be talking to your doctor if it's that severe. 

[00:12:01] Jonathan: Now, this is the first time you've mentioned bacterial infection. I'm guessing that. Everyone listening to this call now feels like they're an expert on viruses after, after covid. So is there also the possibility of this being a viral infection?  

[00:12:13] Will: Definitely. This is another rather important distinction, to be honest with you. So viral infections are of course caused by viruses like rotavirus or norovirus or a norovirus, and these are self-limited infections that typically will last one to three days. This is like the classic 24 hour bug where it hits you so hard. But then, you know, 24 or 30 hours later, actually, you're starting to feel a lot better. If you have abdominal discomfort with a viral infection, it typically will be more on the mild spectrum, or if you have a fever, typically it's a low-grade fever. 
On the flip side, if it's a bacterial infection, then fever and abdominal pain, they can actually be rather intense, and you could also simultaneously see blood in the stool. These are some of the things that would suggest a bacterial infection.  

[00:12:58] Jonathan: What would be causing a bacterial infection?  

[00:13:01] Will: So bacterial infections can be caused by pathogenic gut bugs, things that we've heard of like salmonella, e.coli, or listeria. There are also protozoal causes of diarrhea. Like there's something called Giardia.  

[00:13:16] Jonathan: Why isn't understanding the cause of the infection important Will?  

[00:13:19] Will: So this is really important, Jonathan, because the viral infections are gonna be completely self-limited and taking antibiotics will have literally zero benefit in that setting. They won’t improve the viral infection at all but what they will do is potentially increase your risk of complications, including that they will kill some of your good bacteria. On the flip side, with bacteria and protozoal infections, in some cases, treatment with antibiotics does actually become necessary and appropriate. 

[00:13:47] Jonathan: And do you always treat with antibiotics if it's bacterial?  

[00:13:50] Will: Well, it's important to understand that antibiotics are not going to stop the issue in its tracks. They're only going to reduce the duration of symptoms, and therefore the effect becomes less significant the longer that you wait. So there are some big disadvantages to taking antibiotics. One of them is the effect that they can have on our microbiome.  

[00:14:11] Jonathan: Everyone who's been listening to the shows knows that a healthy microbiome is quite important for good bowel movements in the first place.  

[00:14:17] Will: Yeah, of course. Among other things, um, digestive health and metabolic health are both clearly connected to our microbiome, but also a healthy microbiome helps to protect us from infections by reducing the healthy gut floor that exists inside of us Jonathan. Antibiotics can put us at risk for other infections. One of the specific ones that I worry about is called Srid Difficile, but people have probably heard of this as c diff.  

[00:14:43] Jonathan: And I think looking outside the microbiome, I know there's also this concern about antibiotic resistance. We found a study from Oxford University just last year, which estimated that 1.2 million people died in 2019 as a result of antibiotic resistance. 

[00:14:59] Will: This is definitely becoming a very real concern, Jonathan. And the reality is the more that we use our antibiotics, the less effective that they're going to become in the future. So it's important that we become as judicious as possible when it comes to antibiotic use. 

[00:15:20] Jonathan: Okay, will lots of digest there. Let's get the summary on diarrhea.  

[00:15:24] Will: The summary of diarrhea is that there's a number of different ways that we can think about diarrhea. First of all, diarrhea. It's horrible. We've all been there. It negatively affects our quality of life. Think about was this just a one or two bowel movement thing? If it is, and then you're back to normal, that was probably something in your food. So think about what you were eating in the couple of meals leading up to the diarrhea. On the flip side, if it's three or more bowel movements in a 24-hour period, we start to think about the possibility of infection. When it comes on suddenly and it hits us hard like a rocket ship taking off, we think about infection. Whereas when it's more of a gradual build over the course of weeks to months, that's something where we could think about other causes of this. Most of the time with diarrhea, we don't want to actually use antibiotics.If you have a viral infection, you are compromising your own microbiome. You are increasing your risk of complications, and also we are contributing to antibiotic resistance. On the flip side, if you have a bacterial infection, most of the time we don't need them either, it's going to end up being self-limited. I will say for those who have blood in their stool, have fever, have severe abdominal pain. Or if you're older in age, past age 65, and have other issues, like kidney disease or heart disease. This is the situation where you may want the antibiotics, you should talk to your doctor. That's what you need to do.  

[00:16:47] Jonathan: Well will, thank you very much. If, after today's episode, you'd like to try ZOE's personalized nutrition program to improve your health and hopefully improve some of those good gut bacteria that help keep some of those bad gut bacteria at bay, you can get 10% off by going to I'm Jonathan Wolf. 

[00:17:06] Will: And I'm Will Bulsiewicz. 

[00:17:07] Jonathan: Join us next week for another ZOE podcast.