Zinc carnosine has an unusual double life. In Japan it is a prescription stomach ulcer medicine called polaprezinc, sold as Promac and licensed since 1994. In the United States the same molecule is a dietary supplement, marketed to support the stomach lining, soothe the gut and, in the warmer corners of the internet, to heal leaky gut. The gap between those two identities is the whole story.
Almost all of the human research was done in patients, as a drug: people with diagnosed stomach ulcers, people taking antibiotics for an H. pylori infection, long-term aspirin users with gut injury. The research in healthy people, the people who mostly buy the supplement, is two very small studies that measured a laboratory marker. Here is what the trials actually tested, in whom, and what it means for the zinc you would be swallowing.
The short version
- It is a real ulcer drug, abroad. Polaprezinc has been a prescription medicine for gastric ulcers in Japan since 1994. A foreign drug approval is not evidence that the US supplement works for everyday stomach health.
- The best English-language ulcer trial had no placebo. It compared polaprezinc with another ulcer drug and found them similar, which is not the same as beating a dummy pill.
- For H. pylori it is only an antibiotic add-on. Added to prescribed antibiotics it made eradication a little more likely in a meta-analysis, but the certainty was rated very low, and one trial found no benefit. It does not treat H. pylori by itself.
- The leaky gut claim rests on a lab marker. Two studies in 10 and 8 healthy people blunted a urinary permeability marker. That is not a symptom, and no trial has tested it for indigestion or bloating, and the only reflux study was in infants.
- You are swallowing a meaningful dose of zinc. Zinc is a little under a quarter of the compound by weight. Common doses deliver roughly 8 to 34 mg of elemental zinc, against a 40 mg daily upper limit from all sources.
- Long-term use can deplete copper. Too much zinc for too long lowers copper and can cause anemia. The trials were too short to see it, except one that measured copper falling.
- Ulcers and H. pylori are clinician territory. Bleeding, black stools, weight loss, trouble swallowing or new stomach pain after age 60 need a medical evaluation, not a supplement.
Why zinc carnosine is sold for the stomach
The pitch has a strong anchor most supplements lack: this is a licensed medicine somewhere. Polaprezinc has been prescribed for gastric ulcers in Japan for three decades, and that fact does a lot of quiet work in the marketing. Product pages describe a compound that sticks to the stomach lining and protects it, and some reach further, to the gut barrier, to leaky gut, to healing.
Two things get blended together in that pitch. One is the drug: studied in patients with ulcers and infections, under medical care, at doses set for disease. The other is the supplement: taken by healthy people for general stomach comfort, a use that has barely been studied at all. A foreign drug approval tells you a regulator in another country judged it useful for a specific disease under its own rules. It does not tell you a capsule does anything for an ordinary stomach, and the US sells it as a supplement precisely because it is not an approved drug here.
What zinc carnosine is, and whether the carnosine matters
Zinc carnosine, also written zinc-L-carnosine, is a 1:1 chelate: one atom of zinc bound to one molecule of the dipeptide L-carnosine. Unlike plain zinc salts such as zinc gluconate, it is deliberately poorly soluble. The idea, worked out in animal studies, is that an insoluble particle lingers in the stomach instead of dissolving and being absorbed at once, so it can act where it lands. In rats, labeled polaprezinc stayed in the stomach about twice as long as either zinc or carnosine given separately and concentrated at ulcer sites, an effect the authors put down to that insolubility. No human study has shown it adhering to an ulcer, so this is an animal mechanism, not a demonstrated human one.
A natural question is whether the carnosine does anything beyond carrying the zinc. In the laboratory studies that split the molecule apart, the answer is mostly no. Cell studies of the compound's protective and anti-inflammatory effects found the zinc did the measured work and L-carnosine alone did little, and one found the protection was not due to mopping up free radicals, despite the common antioxidant framing. Carnosine's demonstrated role is physical: it helps keep the complex insoluble so it stays put. These are cell and animal findings. They explain how the compound might behave; they are not evidence that it changes outcomes in people.
The evidence at a glance
| The claim | What was tested | Best evidence | Our read |
|---|---|---|---|
| It heals stomach ulcers | Polaprezinc against rebamipide, another ulcer drug, over 8 weeks with endoscopy, in 224 adults with gastric ulcers in China | An effective rate by endoscopy of 81.5% with polaprezinc and 74.3% with rebamipide (P = 0.16, not a significant difference), with no placebo group | Performs like another prescription ulcer drug in a drug trial. Not shown to beat placebo, and this is a prescription use abroad, not a US supplement claim |
| It clears H. pylori | Polaprezinc added to a course of prescribed triple antibiotics | A 2022 meta-analysis of 3 trials in 396 people: eradication was more likely with the add-on (odds ratio 2.01, 95% confidence interval 1.27 to 3.21), rated very low certainty. One of the three trials found no significant benefit | May help the antibiotics work a little, at very low certainty. It does not treat H. pylori on its own |
| It repairs the gut lining or fixes leaky gut | A urinary sugar-permeability marker after a painkiller or after hard exercise, in healthy volunteers | Two tiny studies: in 10 people on a painkiller the marker did not rise significantly; in 8 after hard exercise the rise was about 70% smaller | A lab marker moved in very small, healthy samples. Not symptoms, not a disease, and leaky gut syndrome is not a recognized diagnosis |
| It protects against painkiller damage | Small-bowel injury in long-term low-dose aspirin users | A 20-person pilot, open-label with no placebo: lesion counts fell within the polaprezinc group and not within the untreated group | Preliminary. No placebo and no between-group result reported, and not a reason for healthy painkiller users to take it |
| It relieves indigestion or dyspepsia | Searched for a trial in functional dyspepsia | No trial found. A 2022 review noted that studies outside H. pylori gastritis do not exist | Unknown. No human evidence |
| It helps acid reflux or heartburn | Searched for an adult reflux trial | No adult trial. One trial in 60 infants did not beat thickened formula on its main regurgitation score | No basis for an adult reflux claim |
| It is a gentle, protective zinc you can take long term | Chronic zinc exposure and copper | NIH guidance, a 2026 review of zinc toxicity, and an 8-week trial in which blood copper fell | A dose delivers roughly 8 to 34 mg of elemental zinc a day, up to about 68 mg at the highest trial dose. High or prolonged intake can cause copper deficiency and anemia, and it has not been shown to spare copper |
These summaries describe research, most of it in patients with a diagnosed condition. They are not claims about what a supplement does. A P value of 0.16 means the difference was not statistically significant, and a surrogate marker is a lab measurement, not a symptom.
A prescription ulcer drug in Japan
The strongest-sounding part of the story is also the part that is furthest from a supplement aisle. Polaprezinc is an approved prescription drug for gastric ulcer in Japan, and later in South Korea. The trials behind that approval date from the early 1990s, are in Japanese, and are not retrievable as English abstracts, so the healing data that regulators relied on cannot be read here.
The clearest English-language trial is more recent. Published in 2022, it randomized 224 adults with gastric ulcers at ten hospitals in China to polaprezinc or to rebamipide, another mucosal-protective ulcer drug, for eight weeks, with the result confirmed by endoscopy. The two drugs came out similar: an effective rate of 81.5% with polaprezinc and 74.3% with rebamipide, a difference that was not statistically significant (P = 0.16). Three things keep that from being as impressive as it looks. There was no placebo group, so the trial shows polaprezinc performing like another drug, not beating a dummy pill. There was no stated margin for declaring the two equivalent, so a non-significant gap between two active drugs is not a formal pass. And the abstract never defines its effective rate, so 81.5% is not the same as a complete-healing rate. This is evidence about a drug used for a diagnosed disease under medical care, not about a supplement for general stomach support.
H. pylori: an add-on to antibiotics, not a treatment
H. pylori is a stomach bacterium behind many ulcers, and it is cleared with a course of antibiotics plus acid suppression. The question the trials asked is narrower than it sounds: does adding polaprezinc to those antibiotics help them work? This is not the same as treating the stomach.
A 2022 meta-analysis pooled three randomized trials, 396 people in all, and found eradication more likely when polaprezinc was added to standard triple therapy, with an odds ratio of 2.01 (95% confidence interval 1.27 to 3.21). The authors rated that evidence very low certainty, and the detail explains why. The largest trial, in 303 people, was open-label and funded by a polaprezinc maker; it raised eradication from 59% on antibiotics alone to about 76 to 77%, but a higher dose added no benefit and caused more side effects. A second, smaller trial was positive. The third found that adding polaprezinc did not significantly raise the cure rate at all, while a different add-on in the same study did. And in the trials that tracked symptoms, people improved in every group, including the one on antibiotics alone, so the symptom relief cannot be pinned on the compound. The honest summary is that it may give the antibiotics a modest lift, on weak evidence, and that it does nothing for H. pylori on its own.
Painkiller damage and the permeability studies
The research most often cited for healthy users is a pair of small studies that measured intestinal permeability, how easily substances cross the gut wall, using a urinary sugar test. Both are surrogate markers, laboratory numbers rather than symptoms, and both come from the same research group.
In the first, published in 2007, 10 healthy volunteers took the anti-inflammatory painkiller indomethacin for five days. On placebo the permeability marker roughly tripled; when zinc carnosine was taken alongside the painkiller, there was no significant rise. In the second, in 2016, 8 volunteers did hard exercise, which also tripled the marker, and two weeks of zinc carnosine blunted that rise by about 70%. These are real, reproducible findings, and they are tiny: a handful of healthy people, an artificial challenge, a lab measurement, from one group whose work was tied to a health-claim application. They do not show that anyone felt better.
A related pilot looked at actual gut injury. Twenty adults on long-term low-dose aspirin, who had small-bowel damage visible on a capsule camera, took polaprezinc or no treatment for four weeks. Lesion counts fell within the polaprezinc group and did not change in the untreated group. It is a hopeful signal, but it was open-label with no placebo, only 20 people, and the published abstract reports the change within each group rather than a head-to-head comparison between them. It is a reason for more research, not a reason for a healthy person taking the occasional painkiller to add a zinc supplement.
Reflux, indigestion and leaky gut: what is missing
For the complaints people most often reach for it, the evidence is not thin, it is absent. A 2022 review of nutritional ingredients for upper digestive symptoms placed zinc carnosine in its lowest evidence category and noted plainly that studies outside H. pylori gastritis do not exist. So:
- Indigestion and functional dyspepsia. No trial. There is no human evidence that zinc carnosine eases ordinary indigestion in people without a specific diagnosis.
- Acid reflux and heartburn. No adult trial. The one reflux study was in 60 infants with regurgitation, and it did not beat thickened formula on its main symptom score. The compound is not thought to work by lowering stomach acid, which is how reflux is usually treated.
- Leaky gut. The claim rests entirely on the two permeability-marker studies above. Leaky gut syndrome is not a recognized medical diagnosis, and in a separate 2025 trial plain zinc did not improve gut-integrity markers. For the wider picture, see our guide to supplements for leaky gut.
- Bloating and IBS. No trial of zinc carnosine for either. The gut-comfort framing on product labels runs well ahead of what has been measured.
The pattern is the same one that runs through our reviews of L-glutamine and peppermint oil: a compound with a real, narrow role in diagnosed disease gets marketed for the everyday symptoms it has never been tested against.
How much zinc you are actually swallowing
Because zinc carnosine is a zinc compound, every dose is also a dose of zinc, and this is the part the gut-lining framing tends to skip. Zinc makes up a little under a quarter of the compound by weight, so the elemental zinc adds up quickly:
- 37.5 mg of zinc carnosine (a common supplement serving): about 8 to 9 mg of zinc.
- 75 mg (the daily dose in the 10-person painkiller study): about 17 mg of zinc.
- 150 mg (the Japanese ulcer-drug dose): about 34 mg of zinc.
- 300 mg (the higher arm of the H. pylori trial): about 68 mg of zinc.
For comparison, the daily requirement is roughly 8 to 11 mg, and the NIH Office of Dietary Supplements sets the adult tolerable upper limit at 40 mg a day. The number that matters most is easy to miss: that limit counts zinc from all sources together, food, a multivitamin, zinc lozenges and this supplement. The 300 mg daily dose used in one trial is over the limit from the pill alone. The 150 mg drug dose reaches about 34 mg, close to the limit before any food is counted. Different brands also declare different amounts of zinc for the same compound weight, so the useful habit is to read the elemental zinc line on the label and add it to everything else you take, not to count the compound weight.
Copper, interactions and who should be careful
In the trials themselves, which ran from five days to eight weeks, zinc carnosine was generally reported as well tolerated, with no serious adverse events and more minor side effects at the highest dose. The catch is that the real long-term risk of any zinc develops over a longer stretch than any of these trials lasted.
- Too much zinc depletes copper. The NIH notes that 50 mg of zinc or more a day over a period of weeks can inhibit copper absorption, and a 2026 review of zinc-induced toxicity found anemia, and low copper in every case, at intakes of roughly 50 mg a day and up over weeks to years, sometimes mistaken for a bone-marrow disorder. An 8-week trial at 150 mg of polaprezinc a day measured a real fall in blood copper, with one person's copper deficiency worsening. Copper deficiency can cause anemia and nerve problems that do not always fully reverse. Nothing shows this compound is gentler on copper than other zinc.
- Antibiotics and other medicines. Zinc can bind quinolone and tetracycline antibiotics and the drug penicillamine and lower how much is absorbed, so they are kept a few hours apart. Taking 25 mg or more of iron at the same time as zinc lowers zinc absorption. This matters directly for H. pylori regimens, which is a reason that decision belongs with the treating clinician.
- Add up your total zinc. A multivitamin, zinc lozenges or high-zinc denture products stack on top of this. Keep the daily total in mind against the 40 mg limit.
- Pregnancy, breastfeeding and children. No study has tested this compound for safety in pregnancy or breastfeeding, and the only trial in children was an efficacy study in infants, not a safety one. The zinc load from a typical adult dose can approach or exceed a child's much lower limit. This is a clinician's call, not a do-it-yourself one.
- Kidney disease and long-term zinc. The clearest copper-deficiency harms from polaprezinc are in dialysis patients taking zinc long term. Anyone taking it for months should have copper checked by a clinician.
An ulcer or an H. pylori infection is diagnosed and treated by a clinician, with endoscopy, a breath or stool test, and prescribed medicine, and a supplement is not a substitute. Doctors treat certain stomach symptoms as warning signs: vomiting blood or black, tarry stools, unintended weight loss, trouble or pain swallowing, persistent vomiting, or a new bout of stomach pain or indigestion starting at age 60 or older, which the American College of Gastroenterology and the Canadian Association of Gastroenterology say should prompt an endoscopy. Any of these means see a clinician rather than self-treat.
Frequently asked questions
Does zinc carnosine heal or repair the stomach lining?
That has been tested mostly in patients, as a drug, not in healthy people. Zinc carnosine is the compound in polaprezinc, a prescription stomach ulcer medicine in Japan since 1994. The clearest English-language trial compared it with another ulcer drug, rebamipide, in 224 people with gastric ulcers, and found the two similar (an endoscopy effective rate of 81.5% versus 74.3%, not a significant difference), with no placebo group. In healthy people, the only stomach-related research is two very small studies that measured a gut permeability marker, not healing of a normal lining. Stomach ulcers need medical diagnosis and care, not self-treatment.
Does zinc carnosine help with H. pylori?
Only as an add-on to prescribed antibiotics, and the evidence is weak. A 2022 meta-analysis of three trials in 396 people found that adding polaprezinc to a standard triple-antibiotic course made eradication more likely (odds ratio 2.01), but rated the certainty very low: the trials were small, two of three were open-label, one was funded by the maker, and one found no significant benefit. It cannot treat H. pylori on its own, and because zinc can reduce how well some antibiotics are absorbed, dosing has to be managed by the clinician treating the infection. H. pylori needs medical testing and treatment.
Does zinc carnosine help acid reflux or heartburn?
No adult trial has tested that. A 2022 review noted that no studies of zinc carnosine for upper digestive symptoms outside H. pylori gastritis exist, so any effect on heartburn or indigestion is unknown. One trial in 60 infants with regurgitation did not beat thickened formula on its main symptom score. The compound is not thought to work by lowering stomach acid. Frequent heartburn is a reason to see a clinician, not to self-treat with a supplement.
Does zinc carnosine fix leaky gut?
Leaky gut syndrome is not a recognized medical diagnosis. Two very small studies tested this: in 10 people on a painkiller, zinc carnosine kept a urinary sugar-permeability marker from rising significantly, and in 8 people after hard exercise it cut the rise by about 70%. That is a lab measurement in healthy volunteers under an artificial challenge, not a symptom and not a disease that was healed. In a separate 2025 trial, plain zinc did not improve gut-integrity markers. Our guide to supplements for leaky gut covers the wider debate.
How much zinc is in zinc carnosine, and can it exceed the safe limit?
About 22 to 23% of the compound is elemental zinc, so 37.5 mg supplies roughly 8 to 9 mg of zinc, 75 mg about 17 mg, 150 mg about 34 mg, and 300 mg about 68 mg. The NIH Office of Dietary Supplements sets the adult upper limit for zinc at 40 mg a day from all sources, which means food, a multivitamin, zinc lozenges and this supplement all count together. The 300 mg daily dose used in one trial is over that limit from the pill alone, and 150 mg a day gets close to it before food is counted. Read the elemental zinc line on the label, not the compound weight, and add up your total.
Can you take zinc carnosine long term, and can it deplete copper?
Long-term safety has not been established. The trials ran 5 days to 8 weeks, which is too short to catch the main concern: too much zinc for too long lowers copper. The NIH notes that 50 mg of zinc or more a day over a period of weeks can inhibit copper absorption, and a 2026 review of zinc toxicity found anemia and low copper in cases taking roughly 50 mg a day and up over weeks to years. In an 8-week trial at 150 mg of polaprezinc a day, blood copper fell and one person's copper deficiency worsened. Anyone taking it for months should have copper checked by a clinician, and it has not been shown to be gentler on copper than other zinc.
Is zinc carnosine the same as polaprezinc, and the same as regular zinc?
Zinc carnosine, zinc-L-carnosine and polaprezinc are the same compound: a 1:1 chelate of zinc and the dipeptide L-carnosine, sold as the prescription drug Promac in Japan and as a supplement (often under the brand PepZin GI) in the US. It is not a plain zinc salt like zinc gluconate or sulfate; it is built to be poorly soluble so it lingers on the stomach lining. The human stomach trials used polaprezinc or unbranded zinc carnosine, not a specific US brand name, so they are evidence for the compound rather than for any one product.
Should you take zinc carnosine with food, and does it interact with medicines?
In Japan the drug is taken after meals, though that is a prescription-label practice, not a tested supplement instruction. On interactions, the NIH Office of Dietary Supplements notes that zinc can bind to quinolone and tetracycline antibiotics and to penicillamine and reduce how much of each is absorbed, so these are kept a few hours apart, and taking 25 mg or more of iron at the same time as zinc can lower zinc absorption. Because zinc competes with copper, long-term use needs copper monitoring. Anyone on prescribed medication should ask a pharmacist before adding it.
The bottom line
Zinc carnosine, or polaprezinc, is a prescription stomach ulcer drug in Japan and a dietary supplement in the US, and the evidence belongs to the drug more than the supplement. In people it has been studied mostly in patients. One trial found it similar to another ulcer drug, with no placebo group. Added to H. pylori antibiotics it made eradication a little more likely, on evidence experts rate very low certainty, and it does nothing for the infection on its own. Two tiny studies blunted a gut permeability lab marker, not symptoms. No trial shows it eases indigestion, reflux or bloating. Every dose also delivers a real amount of zinc, which over the long term can deplete copper, so prolonged use is a conversation to have with a clinician. Ulcers and H. pylori need medical care, not self-treatment.