March 18, 2025Debunking Colonoscopy Myths That Could Be Putting Your Health at RiskA colonoscopy can save your life, but misinformation keeps many people from getting one. A gastroenterologist sets the record straight. Anaissa Ruiz Tejada/Scientific AmericanSUBSCRIBE TO Science QuicklyRachel Feltman: For Scientific Americans Science Quickly, Im Rachel Feltman.Few outpatient medical procedures inspire as much negativity as the colonoscopy. In honor of Colorectal Cancer Awareness Month, weve decided to bust up some of the myths that make people avoid this crucial procedure. My guest today is John Nathanson. Hes a gastroenterologist at NewYork-Presbyterian Columbia University Irving Medical Center.Thanks so much for joining us today.On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.John Nathanson: Its great being here. Thank you for having me.Feltman: So we are here to debunk some colonoscopy myths. First things first, you know, why do you think colonoscopies are, like, so reviled by the general public? I had one to check on some post-COVID GI issues about a year ago, and I was really surprised at how not awful it all was [laughs] based on the general vibe. So, yeah, why do you think they sort of loom so large in peoples minds?Nathanson: Well, absolutely. You know, I think it's a sensitive topic. People, you know, dont normally get these things checked out and dont normally talk about the things that we address in colonoscopy in a normal day-to-day conversation. So I think, for people, theres this mystical nature about it, where they kind of understand what we do but may not have a full understanding of everything, and because its such a sensitive area, people tend to have some misconceptions about it.Feltman: Yeah, so what do colonoscopies do? Why are they important?Nathanson: Colonoscopy is a critical tool in our armamentarium as gastroenterologists. Number one, colonoscopy can be used to diagnose common GI issues like constipation, bleeding, diarrhea without any other cause, but more importantly, and for the general public at large, it can be used as a tool for screening for colon cancer.Feltman: So most people assume colonoscopy prep is gonna be really awful. What does it actually involve, and what is it like?Nathanson: You know, its highly variable from doctor to doctoreverybody recommends their own way of doing things. But for most people it generally involves, a day before your colonoscopy, modifying your diet and taking some sort of laxative to help cleanse the system prior to the procedure.Feltman: And why is getting a good prep in so important for the procedure?Nathanson: Getting a good prep is a critical part of this experience because the better the prep, the more thorough our exam is. So the cleaner the colon, the more we are able to look for precancerous lesions, to make sure theres nothing else developing in the colon and to potentially diagnose some issues that brought people in in the first place.Feltman: Yeah. Is there anything that people can do to make the prep process more easier? I mean, for example, my doctor recommended, you know, slowly changing my diet in the days before, which I found really helpful.Nathanson: Absolutely, thats a great idea. And, you know, we try and make very mild changes to peoples routines so that this is not a disruptive experiencerather, this is just something that you get through very easily.We generally recommend drinking the prep cold; that can sometimes help. Number two is just changing your diet little by little prior to the colonoscopy. Mostly what we recommend is just the entire day before the colonoscopy, be on a liquid diet, but you can do things like drink broth, Jell-O, Popsicles, that type of stuff.Feltman: What are some of the sort of common mistakes people might make in their prep work that might impact the quality of the colonoscopy?Nathanson: Sure, you know, people these days love fiber, and as a gastroenterologist we recommend that people increase fiber in their diet pretty much to everybody.Feltman: Mm-hmm.Nathanson: In the days leading up to your colonoscopy, however, a high-fiber diet may make it more difficult to prep completely for your colonoscopy ...Feltman: Right.Nathanson: So while fiber in general is excellentits great for your health, its great for your digestionit may make the prep process a little bit more complicated. And it may make it so that the prep is not as complete as we need it to be. So generally we recommend a lower-fiber diet in the days leading up to the colonoscopy.Feltman: That makes sense. So moving from the prep into the procedure, you know, in the most not-scary terms, what happens during a colonoscopy?Nathanson: Sure, well, you come into our office, you get an IV in your arm, and youre being monitored by an anesthesiologist, who is giving you medication to keep you comfortable. And as a patient is asleep we put a camera in from below to examine the lining of the colon. While youre asleep we look for any signs of cancer or any signs of developing cancer. And if we see anything irregular or developing, we biopsy it or take it out completely.Feltman: And do you have to be sedated to have a colonoscopy?Nathanson: You dont. We recommend it. We find that when patients are more comfortable, we do a more thorough and complete exam. However, there are patients that choose to forgo anesthesia altogether and do just fine.Feltman: Yeah, well, and relatedly, you know, what about people whove heard that colonoscopies are really painful, either during or even after due to bloating? How bad is it usually?Nathanson: The vast majority of our patients experience almost no discomfort at all. During the procedure patients are incredibly comfortable and are being monitored by an anesthesiologist, who can give them more medication if they experience any discomfort whatsoever. And after the procedure any discomfort is, is minimal as well. Patients usually pass gas very quickly, dont feel any discomfort lasting after the procedure.Feltman: So now that weve demystified the procedure itself a little bit, lets talk about deciding to get one.So what would you say to people who assume they dont need colonoscopies because theyre healthy, they eat right, they dont have any problems in the bathroom?Nathanson: Sure. I, I say to everybody: if you are between 45 and 75, a colonoscopy is right for you for colon cancer screening. This is something that everybody, provided they are healthy enough to undergo anesthesia and healthy enough to undergo the procedure, should be offered as a critical method to screen for and to prevent colon cancer.Feltman: So weve been seeing a lot of studies and stuff in the news about younger folks getting colorectal cancer. Is there anything that people should take away from that in terms of when they should get screened or what symptoms they should be looking out for?Nathanson: For sure, and I think this is an important point to bring upwe are seeing a slight increase in the absolute number of patients under the age of 45 who are being diagnosed with colon cancer.So colonoscopy is only one tool that we use to screen for colon cancer. Its the tool that I generally recommend most often because colonoscopy has the added advantage of being able to detect but also prevent colon cancer. I always say: Dont ignore symptoms. If there are symptoms that are scary, that are new, speak with your doctor to figure out whether or not a colonoscopy is the right test to evaluate whats going on.I will say, starting at 45 is a great time to think about colorectal cancer screening, but if there is a family history, if there is a high-risk genetic condition, you may be a candidate to start screening earlier. For example, if a patient has a family history of colon cancer in a first-degree relative, we generally recommend starting at 40 or 10 years before the age of diagnosiswhatever is earlier. So I always say to talk with your doctor to figure out when you should start screening and start thinking about engaging in this process.Feltman: And if people have, you know, any GI concerns that make them feel like maybe they should be getting a colonoscopy, what should their first steps be?Nathanson: Absolutely. You know, this is what we specialize in, and if patients have any questions about GI symptoms, I always recommend speaking with a gastroenterologist. Working with your doctor is an excellent way to figure out if a colonoscopy may be the right screening test for you and may be the right test to figure out what is going on and what is causing your symptoms.Feltman: I think a lot of people assume that all a colonoscopy can do for you is tell you that youve got colon cancer. What else can come out of these procedures?Nathanson: Yeah, I think thats a dangerous misconception because colonoscopy is an excellent way to actually prevent colon cancer, which is the reason why we push it so much, or we, we really talk with our patients more about getting colonoscopies, because if we find precancerous polyps, we can remove them and prevent them from ever becoming an issue.Feltman: Yeah, thats a huge deal. Are there any other big misconceptions about colonoscopies that you want our listeners to know the truth about?Nathanson: Yeah, that this is an unpleasant experience. I find that most of our patients actually say, Well, that was not much of a problem at all, and if I had known it was so easy, I would have come in sooner.So this is a, a straightforward test, its a safe test, and it is a test that is not associated with significant discomfort.Feltman: Awesome, thanks so much for coming in and helping us dispel some of these myths.Nathanson: Absolutely. Thank you so much for having me.Feltman: Thats all for todays episode. Well be back on Friday with a special look into the science of the hit TV series Severance, featuring the neurosurgeon who helped writers develop the shows titular procedure.Science Quickly is produced by me, Rachel Feltman, along with Fonda Mwangi, Kelso Harper, Naeem Amarsy and Jeff DelViscio. Shayna Posses and Aaron Shattuck fact-check our show. Our theme music was composed by Dominic Smith. Subscribe to Scientific American for more up-to-date and in-depth science news.For Scientific American, this is Rachel Feltman. See you next time!