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Is “leaky gut” a thing?

Can someone have “leaky gut”? We asked our own Dr Miguel that very question. With a doctorate in gut microbiome and mental health and years of expertise in the field, he is just the person to provide us with a legitimate answer. He also shared a few other gems with us. The references are linked to the full text of the articles so they can be used as further reading.

What exactly is “leaky gut”?

“Leaky gut” or “leaky gut syndrome” is a made-up condition based on the actual fact that the gut lining is permeable by nature. Contrary to popular belief, the permeability of the gut is not a bad thing at all. As a matter of fact, a relatively permeable mucous lining is needed so that the nutrients we get from food can make it into the bloodstream. This would not happen if the gut was just a tightly sealed tube.

The more scientifically sound name for leaky gut is “intestinal permeability”, a completely natural process that is happening and changing in intensity 24 hours a day, every day of your life. That means that permeability will continuously increase and decrease as a result of a number of factors, including:

Is “leaky gut” a medical condition?

Some people claim to have been “diagnosed with leaky gut”. This is a way of saying that their intestinal permeability was high. Typically they will have had a test that looks for molecules used as indicators of intestinal permeability. The main molecule used for this purpose is called zonulin. It’s a protein that regulates the opening and closing of the spaces between the cells lining the gut epithelium, known as “tight junctions”.21Fasano A. Zonulin and its regulation of intestinal barrier function: the biological door to inflammation, autoimmunity, and cancer. Physiol Rev. 2011 Jan;91(1):151-75. doi: 10.1152/physrev.00003.2008.

Studies have shown that more zonulin is produced when the mucous layer that coats the gut lining loses its integrity as a result of a derangement in the composition of the gut microbes that inhabit the colon, referred to as dysbiosis.22Safadi JM, Quinton AMG, Lennox BR, Burnet PWJ, Minichino A. Gut dysbiosis in severe mental illness and chronic fatigue: a novel trans-diagnostic construct? A systematic review and meta-analysis. Mol Psychiatry. 2022 Jan;27(1):141-153. doi: 10.1038/s41380-021-01032-1.23Di Tommaso N, Gasbarrini A, Ponziani FR. Intestinal Barrier in Human Health and Disease. Int J Environ Res Public Health. 2021 Dec 6;18(23):12836. doi: 10.3390/ijerph182312836. When the balance between health giving (probiotic) and disease carrying (pathogenic) bacteria is lost, the delicate balance between tolerance and immune response is lost with it, leading to inflammation that contributes to further loss of barrier function. This is when zonulin kicks in, enabling the opening of the tight junctions, and allowing an influx of molecules into the bloodstream, including part-digested food molecules and bacterial cell fragments that can trigger a response by the immune system.24Sturgeon C, Fasano A. Zonulin, a regulator of epithelial and endothelial barrier functions, and its involvement in chronic inflammatory diseases. Tissue Barriers. 2016 Oct 21;4(4):e1251384. doi: 10.1080/21688370.2016.1251384.25Fasano A. All disease begins in the (leaky) gut: role of zonulin-mediated gut permeability in the pathogenesis of some chronic inflammatory diseases. F1000Res. 2020 Jan 31;9:F1000 Faculty Rev-69. doi: 10.12688/f1000research.20510.1.

All of this is hard science. But the flaw with this approach is that zonulin is not a diagnostic molecule. It is known to go up and down dramatically depending on the same factors we’ve covered above, i.e. food, exercise, stress, etc. Additionally, commercially available zonulin tests have been discredited for their inability to accurately identify zolunin. It has become apparent that they identify a whole group of molecules, some of which have opposite roles to that of zonulin.26Massier L, Chakaroun R, Kovacs P, Heiker JT. Blurring the picture in leaky gut research: how shortcomings of zonulin as a biomarker mislead the field of intestinal permeability. Gut. 2021 Sep;70(9):1801-1802. doi: 10.1136/gutjnl-2020-323026.  To make things even more complicated, there are many other molecules that can be measured to assess intestinal permeability. One you’re likely to come across is called lipopolysaccharide, or LPS for short. LPS is produced by certain types of bacteria, mostly pathogens, i.e. those that contribute to disease. It is known to damage the integrity of the protective mucous layer and to contribute to chronic inflammation in the gut.27Page MJ, Kell DB, Pretorius E. The Role of Lipopolysaccharide-Induced Cell Signalling in Chronic Inflammation. Chronic Stress (Thousand Oaks). 2022 Feb 8;6:24705470221076390. doi: 10.1177/24705470221076390.28Candelli M, Franza L, Pignataro G, Ojetti V, Covino M, Piccioni A, Gasbarrini A, Franceschi F. Interaction between Lipopolysaccharide and Gut Microbiota in Inflammatory Bowel Diseases. Int J Mol Sci. 2021 Jun 10;22(12):6242. doi: 10.3390/ijms22126242.

Can intestinal permeability be managed?

Intestinal permeability is self-regulating, so you shouldn’t need to preoccupy yourself with it. However, you could potentially minimise huge spikes in permeability by eating a healthy balanced diet, leading an active life with regular physical activity, and limiting sources of stress. It’s all about being constant and taking a gentle, nurturing, and progressive approach to any changes you make to your diet and lifestyle.

More specifically, drinking kefir has been shown to protect the integrity of the intestinal barrier, helping with the regulation of zonulin.29Peluzio MDCG, Dias MME, Martinez JA, Milagro FI. Kefir and Intestinal Microbiota Modulation: Implications in Human Health. Front Nutr. 2021 Feb 22;8:638740. doi: 10.3389/fnut.2021.638740.30Pražnikar ZJ, Kenig S, Vardjan T, Bizjak MČ, Petelin A. Effects of kefir or milk supplementation on zonulin in overweight subjects. J Dairy Sci. 2020 May;103(5):3961-3970. doi: 10.3168/jds.2019-17696. Additionally, foods that provide prebiotic fibres feed health-giving bacteria that, in turn, produce short-chain fatty acids (SCFAs) like butyrate and acetate. SCFAs are well documented for their ability to keep the intestinal barrier functioning smoothly.31van de Wouw M, Boehme M, Lyte JM, Wiley N, Strain C, O’Sullivan O, Clarke G, Stanton C, Dinan TG, Cryan JF. Short-chain fatty acids: microbial metabolites that alleviate stress-induced brain-gut axis alterations. J Physiol. 2018 Oct;596(20):4923-4944. doi: 10.1113/JP276431.32Martin-Gallausiaux C, Marinelli L, Blottière HM, Larraufie P, Lapaque N. SCFA: mechanisms and functional importance in the gut. Proc Nutr Soc. 2021 Feb;80(1):37-49. doi: 10.1017/S0029665120006916. 

The takeaways

“Leaky gut” is just an informal way to refer to the natural permeability of the gut, which is always changing in response to the conditions that it needs to tackle at any given time. The gut’s relative permeability makes it possible for us to benefit from the nutrients we extract from food, with the help of our gut bacteria. When permeability increases, it almost always manages to find its way back to balance or, a scientists like to call it, “homeostasis”. Think of intestinal permeability as a tidal river, like the Thames. Its natural ebb and flow helps sustain wildlife on its banks. At times of heavy rain it may overflow slightly, and at times of drought it may run a little lower than usual. In any event, that river will always manage to run at the right level for the circumstances.

Scientists have seen increased intestinal permeability in people with conditions ranging from inflammatory bowel disease and to mental health disorders. 33Massier L, Chakaroun R, Kovacs P, Heiker JT. Blurring the picture in leaky gut research: how shortcomings of zonulin as a biomarker mislead the field of intestinal permeability. Gut. 2021 Sep;70(9):1801-1802. doi: 10.1136/gutjnl-2020-323026.34Toribio-Mateas M. Harnessing the Power of Microbiome Assessment Tools as Part of Neuroprotective Nutrition and Lifestyle Medicine Interventions. Microorganisms. 2018 Apr 25;6(2):35. doi: 10.3390/microorganisms6020035. However, that does not mean that “leaky gut” is the cause of these conditions. A much more likely scenario is that there is a complex relationship between lifestyle factors such as diet, exercise, sleep, alcohol, stress, etc., genetics and bacterial composition. Additionally, the presence of gut dysbiosis is a key factor contributing to the development of various conditions in different people.

No test can diagnose anyone with “leaky gut”, even if their gut happens to be slightly more permeable at the time that the test was performed. The truth is that the same test performed 24 hours later may give a completely different result. Following a “leaky gut diet” that excludes whole food groups, or taking a whole bunch of supplements prescribed to heal your gut’s “leakiness” are faddy approaches that are likely to give you health anxiety. You already know that stress contributes to intestinal permeability, so that’s a vicious circle you don’t want to be trapped in! Embrace the fact that it is natural for the gut lining to have varying degrees of permeability depending on what’s going on for you today, and trust it to do its job properly without worrying about it.

Dr Miguel & The Goats


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