Leaky Gut and Inflammation: Overhead flat lay of the Ozzi watermelon pouch and stick packs with chicory root, watermelon, oats and a glass of prepared Ozzi

Leaky Gut and Inflammation: What's Real, What's Marketing, and What Actually Helps (2026)

Leaky Gut and Inflammation: What's Real, What's Marketing, and What Actually Helps (2026)

By Brandon, founder of Ozzi · Published July 18, 2026

TL;DR: Intestinal permeability is real and measurable. "Leaky gut syndrome," the online version where a permeable gut explains your fatigue, brain fog, bloating, and weight, is mostly marketing. The zonulin blood test half the wellness internet sells has failed independent validation twice; the assays appear to detect complement C3 and properdin. Prebiotic fiber has the strongest human evidence, and even that has holes. I sell a fiber and butyrate drink and I'm still telling you the honest version.

Is leaky gut real?

Your gut lining is selectively permeable by design. It lets water, nutrients, and ions through while keeping most bacteria and bacterial debris out. When that selectivity slips, researchers call it increased intestinal permeability. It's a measurable number, not a metaphor.

Mark Camilleri's 2019 review in Gut has the sentence that should end most gut-health funnels: "Whereas inflammatory or ulcerating intestinal diseases result in leaky gut, no such disease can be cured by simply normalising intestinal barrier function."

Diagram of the gut barrier showing the mucus layer, epithelial cells, tight junctions with occludin claudin and ZO-1, and immune cells. From the Ozzi guide: Leaky Gut and Inflammation.

What the research has actually studied (and in whom)

Everything below comes from studies in patients with diagnosed disease or people at genetic high risk, under medical care. It's the strongest evidence in the field, and it says nothing about what any supplement does, including mine.

The best study in the space is Turpin et al., Gastroenterology, 2020. They followed 1,420 healthy first-degree relatives of Crohn's patients, measured intestinal permeability with a lactulose:mannitol ratio, and waited.

An abnormal permeability result was associated with later development of Crohn's disease, hazard ratio 3.03 (95% CI 1.64 to 5.63). It still held when permeability was measured more than 3 years before diagnosis (HR 1.62).

Read the fine print with me. One disease. One genetically high-risk population. An association, not a demonstrated mechanism. Subclinical inflammation predating diagnosis could plausibly drive both. None of it means a permeability test predicts anything in a healthy 44-year-old with bloating.

The other established piece is metabolic endotoxemia. Lipopolysaccharide (LPS), a fragment of gram-negative bacterial cell walls, crosses the barrier, binds TLR4, and triggers cytokine release and low-grade systemic inflammation.

The part gut marketing amputates: the loop runs both ways. Obesity, type 2 diabetes, and fatty liver disease also cause increased permeability.

Can you test for leaky gut?

Researchers can measure permeability. You, at home, mostly cannot buy a meaningful version of that.

The research standard is a dual sugar test. You drink a solution of two sugars, typically lactulose and mannitol (or lactulose and rhamnose), then collect urine for a set window.

What an abnormal result means for a person without a diagnosed intestinal disease remains unestablished. There's no threshold that says "treat this."

The zonulin problem

In 2011, Alessio Fasano published a major review in Physiological Reviews proposing zonulin as a physiological regulator of intestinal tight junctions, identified as pre-haptoglobin 2.

Commercial ELISA kits followed. Then direct-to-consumer testing companies.

In 2018, Scheffler and colleagues published a validation study in Frontiers in Endocrinology across 376 samples. The widely used commercial ELISA did not detect the precursor of haptoglobin 2. It recognized properdin instead. Fasano, who originated the zonulin concept, is a co-author on that paper.

In 2019, Ajamian and colleagues replicated the problem independently in PLoS One, under a title that does the work for me: "Serum zonulin as a marker of intestinal mucosal barrier function: May not be what it seems." The detected antigen included haptoglobin and complement C3.

The honest answer for anyone holding a zonulin result: the assay behind that number has failed independent validation twice, and the field has known since 2018. Whatever you paid, you did not buy a permeability measurement.

What actually increases intestinal permeability?

Overhead flat lay of whole food fiber sources including oats, green banana, almonds and flaxseed

Strenuous exercise. The cleanest human demonstration in the field. In a 2022 Beneficial Microbes study of 126 people, 1 hour of treadmill running increased the lactulose/rhamnose ratio by roughly 100% (p=0.0001). Researchers use it deliberately as a model, because it works that reliably.

It's transient and reversible.

NSAIDs. Ibuprofen, naproxen, aspirin. Well documented as increasing small intestinal permeability. The fix is obvious: don't take them casually, especially not habitually before workouts.

Alcohol. Also well documented, dose-dependent, consistent across the literature.

A 2024 human crossover trial in International Journal of Molecular Sciences put 15 participants through 2 weeks of a high-fat diet versus 2 weeks of high-carbohydrate.

It produced no tight-junction differences. Postprandial endotoxemia stayed low and unchanged. The authors' phrasing: "the healthy gut can adapt."

How does butyrate fit in?

Butyrate is a short-chain fatty acid produced when gut bacteria ferment fiber in your colon. Butyrate is the primary energy source for the cells lining your colon, which is a plain physiological fact and my favorite one in this whole area.

The mechanistic story is genuinely elegant. Kelly et al. published it in Cell Host & Microbe in 2015, and I want to be exact about what kind of study it was: rodents and cell culture. Not humans.

The experiment has never been run end to end in a person: butyrate in, colonocyte oxygen consumption traced to HIF stabilization to barrier gene expression to a clinical outcome. The mouse chain is complete. The human chain is missing.

I sell butyrate. I'd love to tell you the human data is there. It isn't. The longer version is in butyrate and GLP-1 and gut health and GLP-1.

While I'm here: any GLP-1 signaling from butyrate is preclinical. Rodents and cells. I won't pretend otherwise.

What does the evidence say actually helps?

A bedside table at morning with books, reading glasses and a glass of prepared Ozzi
Intervention Best human evidence Honest grade
Prebiotics / fermentable fiber 2025 meta-analysis: LPS reduced, SMD -0.88 (95% CI -1.28 to -0.47), 16 RCTs, n=792, high certainty. Caveat: I²=85.7%, and LPS is a proxy. B. Strongest thing here, on a surrogate endpoint.
Probiotics 2024 review, 26 studies: 11 of 12 animal studies positive. Human trials "inconsistent, with half reporting reductions in serum LPS and half reporting no differences." C. The translation gap, quantified.
Avoiding habitual NSAIDs Consistent human evidence that NSAIDs increase small intestinal permeability. A-. Talk to your doctor if you take them for a reason.
Moderating alcohol Well-documented, dose-dependent effect in humans. A-. Boring. Works.
"Gut repair" protocols, L-glutamine stacks, collagen powders No FDA-approved agent targets the epithelial barrier. Barrier clinical data remain largely correlative. F for the marketing. Incomplete for the science.
Zonulin testing Failed independent assay validation twice. ELISAs may measure "unknown proteins." F. Don't buy it.

Prebiotic fiber feeds butyrate-producing bacteria. More in prebiotic fiber and the best fiber for appetite control.

Where Ozzi fits

Ozzi Crave Crusher is a cold-water drink stick built for food noise, night cravings, and the out-of-control feeling that brings most people here. Appetite is the job.

Ozzi is not a leaky gut intervention. It isn't tested as one and it isn't sold as one, and given what the barrier literature looks like, there's no product I'd call one.

If fiber is new to you, ramp slowly; bloating and gas are common early on. See bloating and constipation relief.

A fiber and butyrate drink, sold honestly

Ozzi Crave Crusher is a cold-water stick with L-lysine butyrate. No stimulants. Vegan. Built for food noise and night cravings.

14-Day Ozzi Challenge: Take it for 14 straight days. If your cravings and food noise aren't quieter, we'll refund your first bag.

Try Crave Crusher

FAQ

Is leaky gut a real diagnosis?

Intestinal permeability is real and measurable. "Leaky gut syndrome" as a diagnosis is not recognized. A 2024 review by Mayo Clinic gastroenterologists says it is not "currently accepted as a formal medical diagnosis" and that "no validated test currently exists to make this diagnosis."

How do I fix leaky gut?

There's no validated protocol, because there's no validated diagnosis to fix. The defensible moves are removing known causes (habitual NSAIDs, heavy alcohol) and eating fermentable fiber. Persistent GI symptoms deserve a gastroenterologist.

I already paid for a zonulin test. What does my result mean?

Your zonulin test result probably does not mean what you were told. Since the assay appears to pick up complement components, an elevated result may reflect inflammation rather than permeability. That's frustrating, and it's not your fault for buying it.

About the author. Brandon is the founder of Ozzi. He built Crave Crusher after getting tired of night cravings and of supplement companies citing mouse studies like they're clinical trials. He does Reddit AMAs and answers the hostile questions first. More in what is GLP-1.

This article is educational and isn't medical advice. Ozzi Crave Crusher is a dietary supplement and isn't intended to diagnose, treat, cure, or prevent any disease. Persistent digestive symptoms deserve a doctor, not a supplement.

References

  1. Camilleri M. Leaky gut: mechanisms, measurement and clinical implications in humans. Gut. 2019;68(8):1516-1526. PMID: 31076401. doi:10.1136/gutjnl-2019-318427
  2. Leaky Gut Syndrome: Myths and Management. Gastroenterol Hepatol (N Y). 2024. PMID: 39193076. PMC11345991
  3. Odenwald MA, Turner JR. The intestinal epithelial barrier: a therapeutic target? Nat Rev Gastroenterol Hepatol. 2017;14(1):9-21. PMID: 27848962. doi:10.1038/nrgastro.2016.169
  4. Turpin W, Lee SH, Raygoza Garay JA, et al. Increased Intestinal Permeability Is Associated With Later Development of Crohn's Disease. Gastroenterology. 2020;159(6):2092-2100.e5. PMID: 32791132. doi:10.1053/j.gastro.2020.08.005
  5. Safety of Bif195, employing a human exercise-induced intestinal permeability model. Benef Microbes. 2022. PMID: 35866597. doi:10.3920/BM2021.0173
  6. Scheffler L, Crane A, Heyne H, et al. Widely Used Commercial ELISA Does Not Detect Precursor of Haptoglobin2, but Recognizes Properdin as a Potential Second Member of the Zonulin Family. Front Endocrinol (Lausanne). 2018;9:22. PMID: 29459849. doi:10.3389/fendo.2018.00022
  7. Ajamian M, Steer D, Rosella G, Gibson PR. Serum zonulin as a marker of intestinal mucosal barrier function: May not be what it seems. PLoS One. 2019;14(1):e0210728. PMID: 30640940. doi:10.1371/journal.pone.0210728
  8. Massier 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;70(9):1801-1802. PMID: 33037053. doi:10.1136/gutjnl-2020-323026
  9. Fasano A. Zonulin and its regulation of intestinal barrier function: the biological door to inflammation, autoimmunity, and cancer. Physiol Rev. 2011;91(1):151-175. PMID: 21248165. doi:10.1152/physrev.00003.2008
  10. Kelly CJ, Zheng L, Campbell EL, et al. Crosstalk between Microbiota-Derived Short-Chain Fatty Acids and Intestinal Epithelial HIF Augments Tissue Barrier Function. Cell Host Microbe. 2015;17(5):662-671. PMID: 25865369. doi:10.1016/j.chom.2015.03.005
  11. Desai MS, Seekatz AM, Koropatkin NM, et al. A Dietary Fiber-Deprived Gut Microbiota Degrades the Colonic Mucus Barrier and Enhances Pathogen Susceptibility. Cell. 2016;167(5):1339-1353.e21. PMID: 27863247. doi:10.1016/j.cell.2016.10.043
  12. Role of Metabolic Endotoxemia in Systemic Inflammation and Potential Interventions. Front Immunol. 2021;11:594150. PMID: 33505393. doi:10.3389/fimmu.2020.594150
  13. Intestinal Ketogenesis and Permeability. Int J Mol Sci. 2024;25(12):6555. PMID: 38928261. doi:10.3390/ijms25126555
  14. DiMattia Z, et al. Effect of Probiotic Supplementation on Intestinal Permeability in Overweight and Obesity: A Systematic Review of Randomized Controlled Trials and Animal Studies. Adv Nutr. 2024;15(1):100162. PMID: 38072119.
  15. Ghorbani Z, et al. Reinforcing gut integrity: A systematic review and meta-analysis of clinical trials assessing probiotics, synbiotics, and prebiotics on intestinal permeability markers. Pharmacol Res. 2025;216:107780. PMID: 40378939. doi:10.1016/j.phrs.2025.107780
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