After I mentioned it in last week’s 10 Principles of Primal Living (Finally) Getting Mainstream Media Coverage  post, several readers emailed asking about leaky gut. What is it? How do I know if I have it? Why should I care if I have it? What do I do if I have it? And so on. Turns out many and maybe most people have but a vague idea of what leaky gut actually means.
Today, I’m going to fix that.
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.
Another way is to measure levels of blood zonulin, a reliable marker of intestinal permeability . You might have trouble convincing your doctor to order this one.
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.
Inflammatory bowel disease (IBD): Patients with Crohn’s disease, an inflammatory bowel disease characterized by severe inflammation of the gut lining, tend to have leaky gut . And in general IBD, which includes Crohn’s and ulcerative colitis, high intestinal permeability precedes the development of the disease .
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.
Food allergies and intolerances: The transportation of the food allergen across the gut lining appears to be a necessary step in the development  of a food allergy, and a 2011 review  concluded that an overly leaky gut facilitates this transportation and leads to the inducement of allergy.
Autism: Children with autism and their first-degree relatives tend to have abnormal gut permeability , suggesting a gene-environment component to autism. This is present in some, but not all people with autism .
Rheumatoid arthritis, ankylosing spondylitis, and other autoimmune diseases: Both RA and AS have been linked to leaky gut , and the connection may hold for other autoimmune diseases, too.
Obesity and metabolic syndrome: Both obesity and metabolic syndrome are often linked with intestinal permeability, and a recent paper  explores all the potential mechanisms that might explain the link.
Depression: By some accounts, 35% of depressed patients have leaky gut .
Eczema: Going back as far as 1986 , researchers have found leaky gut to be common in eczema patients.
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: http://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.
Too much alcohol. Ethanol increases intestinal permeability  by changing the gene expression of the proteins involved in tight junction function. If you do drink, be sure to follow best practices  and definitely do not drink on an empty stomach. Alcohol also depletes zinc , which is a crucial pro-gut nutrient.
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.
Take whey protein isolate and glutamine. Both supplements have been shown to reduce leaky gut in patients with Crohn’s disease .
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.
Take probiotics and/or (preferably “and”) eat fermented food. Prebiotics are important, but you also need to provide the right gut bugs if you’re deficient. You can do it with both supplements  and food. L. rhamnosus and L. reuteri supplements reduce leaky gut and improve symptoms  in kids with atopic dermatitis. L. rhamnosus also helps restore the gut barrier in kids with acute gastroenteritis . In rats with leaky gut, yogurt improves gut barrier function .
Get adequate sunlight and/or take vitamin D3 supplements. Vitamin D helps protect against injuries to the intestinal lining , while a vitamin D deficiency promotes intestinal permeability  and inflammation.
Get enough zinc. Oysters, red meat, supplements – zinc supplementation reduces leaky gut .
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!
Prefer listening to reading? Get an audio recording of this blog post, and subscribe to the Primal Blueprint Podcast on iTunes for instant access to all past, present and future episodes here .