In most popular conceptions of human physiology, the gut exists primarily as a passive conduit along which food travels and breaks down for digestion and absorption. It’s where bacteria hang out and digestive enzymes go to work. It’s a “place,” an inert tunnel made of flesh and mucus. Lots of things happen there but the gut itself isn’t doing much.
Except that the gut serves another very important and active role: as a dynamic, selective barrier between us and the external world with all its nasties. Dynamic in that it responds differently depending on what’s trying to get through. Selective in that it’s supposed to let in good things and keep out harmful things.
Lining the gut are epithelial cells whose cell membranes fuse together to form protein complexes called tight junctions. The tight junction is the doorman. These are the dynamic, selective parts of the gut. Like the doorman, the tight junction’s job is to discern between what belongs inside and what doesn’t. What gets passage through the gut lining into our body and what is denied. Tight junctions keep out pathogens, antigens, and toxins while admitting nutrients and water.
That’s in a perfect world, though. Sometimes the doorman shows up to work drunk. Sometimes the doorman can’t turn down the $100 bill enfolded in a handshake. Sometimes the doorman lets the pretty girl and all her friends cut in line. Many variables can affect the doorman’s ability to discern between who belongs and who doesn’t. And the same goes for intestinal tight junctions.
How do you know if you have leaky gut?
Everyone’s gut is a little leaky, a little permissive if not downright permeable.
One way is to take an intestinal permeability test. You drink a solution containing a pre-measured amount of mannitol and lactulose, two indigestible sugars. You collect your urine over the next 6 hours and measure the amount of excreted mannitol and lactulose to determine how much permeated through your gut.
You can also look at the list of conditions commonly associated with elevated intestinal permeability. If you have any or all of them, you may have leaky gut. Put another way, if you have leaky gut, you may be at a greater risk for some of these. What are they?
Celiac disease: When gluten is broken up into fragments in the gut, those fragments induce the release of zonulin, which tells the tight junctions to become more permeable. This happens to everyone whose guts come into contact with those gluten fragments, but the effect is enhanced in people with celiac. Their gluten-induced leaky gut is way more leaky than it should be, and it stays leaky long after the gluten has been gone. In fact, before direct testing for gluten antibodies and intestinal damage became widespread, a common test for celiac used to be the very same intestinal permeability assessment I just mentioned.
Irritable bowel syndrome (IBS): As discussed yesterday, IBS patients often show increased gut permeability. Some researchers suggest that leaky gut leads to the kind of chronic, low-level inflammation that characterizes IBS.
Interesting, huh? Leaky gut really gets around. It may not be the whole story, and some of these connections may be coincidental, but plausible mechanisms exist for most of them and I’m confident that fixing leaky gut will improve many seemingly disparate health problems.
Plus, even if it wasn’t the proximate cause of your health problems, leaky gut probably isn’t helping you get better and you should try to fix it. Multiple feedback loops which make teasing apart cause and effect nearly impossible also make it possible to step in the middle of the loop(s) and break it up.
Leaky gut: what it is, how to know if you have it, and what to do about it: https://ctt.ec/5f8B4+
What should you do?
First, avoid things that might cause it.
Gluten. Gluten begets gliadin releases zonulin induces leaky gut. I discussed this in the celiac section above, but it’s important to reiterate that gliadin has this leaky effect on every gut, not just in celiacs. Celiacs just get it worse than non-celiacs.
Stress. Stress can directly induce leaky gut (PDF) and stress can take many forms, as we all know. Bad finances, marital strife, unemployment, too much exercise, lack of sleep, extended combat training, and chronic under-eating all qualify as significant stressors with the potential to cause leaky gut, especially chronically and in concert.
Poor sleep habits. In one recent study, mice whose circadian rhythms were disrupted were more susceptible to liver damage and alcohol-induced intestinal permeability.
NSAIDs. Non-steroidal anti-inflammatory drugs like aspirin and ibuprofen can be helpful in certain situations, but they are far from benign. One of their worst and most pronounced effects is leaky gut.
Then, take proactive steps to improve gut barrier function.
Try resistant starch and other prebiotics. Whether potato starch, green bananas/plantains, mung bean starch, inulin powder, jersualem artichokes, leeks, pectin, or apples, start eating RS and other prebiotics on a regular basis. They increase butyrate production (which reduces intestinal permeability) and support the growth and maintenance of healthy microbial populations.
Drink bone broth, eat gelatinous cuts of meat. It’s such a staple piece of advice in the “healing your gut” scene that it’s worth including. Plus, oxtails are magic, and science can’t quite explain magic just yet.
Exercise intelligently. Intense, protracted exercise induces leaky gut. This is normally transient and totally manageable, but if taken to the extreme as in chronic cardio, exercise-induced leaky gut can become a chronic condition. The same goes for any kind of chronic exercise. Even too much strength training can probably do it, though you’d have to do a ton of volume without much rest. Meanwhile, moderate exercise improves gut barrier function. The tried and true triumvirate of lifting heavy things, walking lots, and sprinting occasionally is the safest bet.
Check out a free Solving Leaky Gut webinar this Thursday. If you want to hear direct from the experts who’ve helped patients solve and cure leaky gut and many of the aforementioned health issues related to it, you’ll want to attend the webinar this Thursday, May 8 at 9 PM Eastern. It’s part of a larger package called Solving Leaky Gut that gets way deeper into the condition and offers specific, proven tips, tricks, and strategies for improving your gut function, reducing food intolerances, and boosting immune health.
If all this stuff seems daunting and far-reaching, that’s because it is daunting and far-reaching. The gut affects nearly everything. But look at the bright side: fixing your gut may be the key to good health for many of you. It’s actually quite empowering. Don’t you think?
Thanks for reading, everyone!
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Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.