Zinc-carnosine for gastric ulcers and leaky gut: the Japanese trial record

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Zinc-carnosine (polaprezinc) is a chelated complex that has been used as a prescription anti-ulcer drug in Japan for decades and is now sold internationally as a gut-health supplement. Its identity is unusual: it is neither a pure zinc salt nor a pure peptide, but a 1:1 chelate engineered to dissolve slowly and coat damaged mucosa. The clinical record is a mix of older Japanese ulcer work, more recent randomized trials in post-endoscopy ulcers and Helicobacter pylori eradication, and one tightly designed UK permeability study. Below is what the trials actually show, and where the evidence is thinner than the marketing suggests.

What zinc-carnosine actually is

Polaprezinc is a 1:1 chelate of zinc and the dipeptide L-carnosine (beta-alanyl-L-histidine), chemically N-(3-aminopropionyl)-L-histidinato zinc. Because the chelate is poorly soluble at gastric pH, it adheres to ulcerated tissue and releases zinc locally rather than being absorbed straight away the way a simple zinc salt would be. That local delivery is the point: it puts zinc and carnosine directly onto the mucosal surface that needs repair.

The proposed mechanisms are reasonably well characterized in animal and cell work. Polaprezinc scavenges free radicals, stabilizes cell membranes, and induces protective stress proteins in the gastric lining. A rat study found it is a potent inducer of heme oxygenase-1, an antioxidant enzyme, and that blocking that enzyme abolished much of its protection against acid-induced lesions (Ueda 2009). Separate work shows it raises gastric heat-shock protein 72, an endogenous cytoprotective factor, and that this induction restores mucosal defenses suppressed by acid-blocking drugs (Wada 2006). In a wounded-cell-monolayer model, zinc-carnosine roughly tripled both the migration and proliferation of intestinal epithelial cells (Mahmood 2007) — the two processes that close a healing wound.

Gastric ulcer healing

Polaprezinc was developed and approved in Japan as a mucosal-protective anti-ulcer agent, and the bulk of the older healing data sits in the Japanese literature, much of it not indexed in detail in English. The cleaner modern evidence comes from artificial ulcers created by endoscopic submucosal dissection (ESD), the procedure used to remove early gastric tumors. In a randomized trial of 210 patients with ESD-induced ulcers, adding polaprezinc 150 mg/day to pantoprazole was non-inferior to adding rebamipide, with four-week healing rates around 90% in both arms (Jung 2021). An earlier randomized study of 163 ESD patients found that adding polaprezinc to lansoprazole significantly improved ulcer healing and cut the rate of an awkward healing artifact (basal protrusion) from about 21% to roughly 1% (Inaba 2010). A 2025 network meta-analysis of 20 trials of mucosal protectants after ESD placed polaprezinc among the agents that, combined with a proton-pump inhibitor (PPI), accelerate healing relative to a PPI alone — though the authors stressed the evidence is regionally concentrated and hypothesis-generating (Chen 2025). The honest read: polaprezinc helps ulcers heal, but it is an adjunct to acid suppression, not a replacement for it.

Adjunctive use with H. pylori eradication

One of the better-known findings is that polaprezinc improves H. pylori cure rates when bolted onto standard antibiotics. In a randomized trial of 66 infected patients, adding polaprezinc 150 mg twice daily to a seven-day lansoprazole/amoxicillin/clarithromycin regimen raised eradication from 77% to 94% on intention-to-treat analysis (86% to 100% per protocol) — a statistically significant gain (Kashimura 1999). A 2022 systematic review and meta-analysis pooling three randomized trials (396 patients) confirmed the direction of effect: polaprezinc-based regimens roughly doubled the odds of eradication versus triple therapy alone (odds ratio 2.01, 95% CI 1.27–3.21) with no increase in adverse events (Mahmoud 2022). The reviewers were careful to note the evidence base is still small. The likely mechanism is better mucosal healing plus some direct anti-bacterial and urease-inhibiting activity, rather than antibiotic potentiation per se.

NSAID-induced gastric and small-bowel injury

The single most-cited study behind the consumer supplement is a UK crossover trial in healthy volunteers. Indomethacin (50 mg three times daily for five days) roughly tripled small-bowel permeability, measured as the lactulose:rhamnose ratio (from about 0.35 to 0.88); when zinc-carnosine 37.5 mg twice daily was co-administered, the rise in permeability was effectively abolished (Mahmood 2007). The same paper showed dose-dependent reductions in gastric and small-intestinal injury in animal models. It is a small, mechanistically tight study, and it is the strongest piece of evidence for the "gut barrier" and "leaky gut" framing used to sell the product outside Japan. Worth a caveat: a randomized, placebo-controlled trial in dogs given aspirin found that zinc-L-carnosine (with vitamin E) did not attenuate gastroduodenal injury (Baan 2010) — a reminder that protection against one NSAID in one model does not guarantee protection against another.

Ulcerative colitis and other uses

Interest has extended to inflammatory bowel disease. A small randomized, investigator-blinded trial of 28 patients with active ulcerative colitis found that polaprezinc enemas added to standard induction therapy improved endoscopic and clinical scores, with clinical response or remission in 71% of the polaprezinc group versus 10% of controls (Itagaki 2014). The trial is small and the enema route is not how consumers take the oral supplement, so this should be read as a promising signal rather than established practice. Claims for functional dyspepsia and reflux are weaker still: there is no high-quality randomized evidence that zinc-carnosine meaningfully improves reflux esophagitis, and dyspepsia data are heterogeneous and modest.

Dosing, safety, and the bottom line

Therapeutic trials have used 75 mg twice daily (the dose in the UK permeability study and many supplements, providing roughly 16 mg elemental zinc per dose) or 150 mg/day for ulcer and eradication indications, typically for four to eight weeks. Tolerability is good across the trial record; the most common complaints are mild constipation or nausea, and adverse-event rates in the H. pylori meta-analysis did not differ from controls. The main long-term concern is the one that applies to any sustained zinc load: zinc competes with copper for absorption, so high doses taken for months can drive copper deficiency, and extended supratherapeutic courses should be monitored. Practically, zinc-carnosine has a defensible role as a short-course adjunct — alongside a PPI for ulcer healing, alongside antibiotics for H. pylori, or as a barrier-protective agent during NSAID exposure — but it is not a substitute for acid suppression when that is genuinely indicated.

Sources

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