Helicobacter pylori (H. pylori)

Gut · §69

A spiral-shaped bacterium lives in the stomach of roughly half the world's adults, quietly inflaming the lining for decades, and it is the single biggest cause of stomach cancer on Earth. Most people who carry Helicobacter pylori were infected before age ten — typically from a parent — and will keep it for life unless treated. Two weeks of the right antibiotics clears it for good and cuts gastric cancer risk by roughly a third to a half, plus most ulcers, plus a quiet drain on iron and vitamin B12.

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The headline win is cancer: clearing this bug cuts stomach cancer risk by a third in everyone, and by more than half if a parent or sibling has had the disease. The everyday win is your stomach lining stops being chronically inflamed — ulcers heal, dyspepsia eases, and the slow leak of iron and B₁₂ stops. Two weeks of four pills a day, then a single follow-up test. Cheap, well-studied, and one of the genuinely settled wins in modern gut medicine.

Stomach acid is supposed to kill almost everything that lands in it. H. pylori survives by carrying its own neutralising plant: an enzyme called urease that turns urea into ammonia, raising the pH in a small bubble around the bug long enough for it to swim through the acid and burrow under the mucus layer. Once it reaches the stomach wall, it latches onto the cells and stays there — for the rest of your life if nothing changes Kao et al., Biomed J 2016.

Two of its proteins do most of the damage. One, called CagA, gets injected directly into your stomach cells through a tiny molecular syringe and scrambles their internal wiring — how they divide, how they connect to their neighbours, how they signal. The other, VacA, punches channels in the cell membrane and helps the bacterium hide from your immune system. Strains carrying CagA roughly double the lifetime risk of stomach cancer compared with strains that don't Kao et al., Biomed J 2016.

The end result is chronic inflammation of the stomach lining — universal in everyone infected, even those who feel nothing — that grinds on for decades. Over years, the inflammation can wear the lining flat (atrophy), then the cells start to look more like intestinal cells than stomach cells (metaplasia), then a few of them start to look abnormal (dysplasia), then a few of those turn into cancer. This is a slow staircase, not a flip; most carriers never reach the top step. But when they do, this bug is what put them there Sugano et al., Gut 2015.

What the evidence actually shows

The World Health Organization's cancer agency classified H. pylori as a definite human carcinogen in 1994 — in the same group as tobacco and asbestos IARC Monographs Vol. 61, 1994. Roughly 89% of the world's non-cardia stomach cancers — about 660,000 cases each year — would not happen without it Plummer et al., Int J Cancer 2015. In Japan and Korea the figure is over 95%.

You don't have to take the population statistics on faith. The randomised-trial evidence is rare in oncology, and we have it here.

The Cochrane meta-analysis pooling all the trials in healthy infected adults estimates a 36% reduction in stomach cancer incidence and a 22% reduction in stomach cancer mortality from eradication Ford et al., Cochrane 2020. Those numbers come mostly from East Asian populations, where stomach cancer is common; in low-incidence Western settings the proportional reduction may be similar but the absolute number of cancers prevented per person treated is smaller.

The ulcer effect is more dramatic and faster. Before eradication, peptic ulcers came back in 60–80% of patients within a year on acid-suppressing pills alone. After eradication, that drops to under 10% Chey et al., ACG Guideline 2024. This was the original Marshall–Warren Nobel-Prize result, and it remains one of the largest treatment effects in all of internal medicine.

For one rare stomach cancer — gastric MALT lymphoma — eradication is the entire treatment. About 77% of early-stage cases go into complete remission with antibiotics alone, no chemotherapy or radiation needed Zullo et al., Clin Gastroenterol Hepatol 2010. There is no other human cancer where antibiotics are first-line cure.

What untreated infection costs you over time

For the first few decades, often nothing you notice. The bug doesn't hurt; the gastritis is silent. This is the trap: by the time it announces itself, the stomach lining has been remodelled in ways that don't fully reverse.

Somewhere in your forties or fifties — earlier in higher-risk populations — a meaningful slice of carriers start running into the consequences. About one in ten will get a peptic ulcer at some point: the gnawing pain that wakes you at 2 a.m., the meal you can't finish, the GP visit that becomes an endoscopy. A smaller fraction of carriers — under 1% in a typical Western adult, several percent if you're East Asian or have a parent or sibling with stomach cancer — will be told a biopsy showed something the pathologist wants to follow.

The quieter cost runs in parallel. Chronic gastritis slowly breaks the machinery that absorbs iron and vitamin B₁₂. Infected adults are roughly twice as likely to be iron-deficient as uninfected adults Muhsen & Cohen, Helicobacter 2008 — and in real life this looks like the colleague who is always a little pale and a little tired, who tries multivitamins for years before anyone thinks to test for the bug behind it. Untreated B₁₂ loss takes longer but goes further: foggy thinking, low mood, eventually a kind of nerve damage in the spinal cord that doesn't fully recover even with replacement Lahner et al., World J Gastroenterol 2018.

The headline cost is cancer. Stomach cancer rarely makes noise until it's late, and late-stage stomach cancer has a five-year survival under one in three in most countries. The bug responsible for nearly nine in ten of those cases has been treatable for thirty years.

Who should actually get tested

Not everyone. The case for testing is strongest when one of these is true:

You have a parent, sibling, or child who has had stomach cancer. The strongest case in the trial evidence — a 55% reduction in your own cancer risk from eradication, more if it works the first time Choi et al., NEJM 2020.
You have a current or past stomach or duodenal ulcer. Test everyone, every time — H. pylori is the cause until proven otherwise, and untreated infection means the ulcer is coming back Chey et al., ACG Guideline 2024.
You have persistent upper-stomach pain or indigestion under age 60 with no alarm features. Test before scoping; treating a positive often resolves the problem without an endoscopy.
You have unexplained iron-deficiency anaemia or unexplained low B₁₂. After the standard gut work-up rules out obvious causes, this bug is on the short list Maastricht VI Consensus, Gut 2022.
You're starting long-term daily aspirin or NSAIDs, or planning to take a daily acid-suppressing pill for years. The combination with active infection raises ulcer and complication risk.
You grew up in (or your parents grew up in) East Asia, Andean Latin America, parts of Eastern Europe, or sub-Saharan Africa. Background prevalence and per-person cancer risk are both higher; the risk follows you even after a move.

If none of these apply and you have no symptoms, the case is weaker. Eradicating millions of asymptomatic low-risk adults in places like Northern Europe or North America burns through antibiotics and would prevent relatively few cancers per course. Reasonable people, including major guidelines, draw the line in different places here. If you want to be tested and have no contraindications, the cost is low and the downside is small.

How testing and treatment actually work

Two active-infection tests dominate, both non-invasive and accurate. The urea breath test has you drink a small dose of labelled urea; if the bug is there, its urease enzyme splits the urea and you exhale labelled carbon dioxide. Sensitivity around 94% at high specificity Best et al., Cochrane 2018. The monoclonal stool antigen test looks for bacterial protein in a single stool sample; sensitivity around 83% Best et al., Cochrane 2018. Either is fine for diagnosis. Blood-antibody testing is what most casual order-online kits use, and it can't tell active from past infection — antibodies linger for years after the bug is gone. Skip it.

One trap: both active-infection tests give false negatives if you've recently taken a proton-pump inhibitor (omeprazole and friends) or antibiotics. Stop the PPI for two weeks and stay off antibiotics for four weeks before testing. If you can't stop the PPI, a biopsy at endoscopy is the fallback.

Treatment is two weeks of pills. The current first-line in nearly every modern guideline is bismuth quadruple therapy — an acid-suppressing pill plus bismuth plus two antibiotics (tetracycline and metronidazole) — because it works regardless of whether your strain is resistant to the older antibiotic clarithromycin Chey et al., ACG Guideline 2024 Maastricht VI Consensus, Gut 2022. Older "triple therapy" with clarithromycin is no longer recommended as an empiric first try, because roughly a third of strains worldwide are now resistant to it Hu et al., Ann Clin Microbiol Antimicrob 2023.

A newer option, vonoprazan-based therapy (with amoxicillin alone, or with amoxicillin and clarithromycin), is approved in the US and works particularly well against clarithromycin-resistant strains — eradication around 65–70% in resistant infections versus ~32% with the old regimen in the head-to-head trial Chey et al., Gastroenterology 2022 (PHALCON-HP). It's a reasonable choice where bismuth is poorly tolerated or unavailable.

Cost, in the US: stool antigen $50–150, urea breath test $100–300, branded eradication packs $650–900 wholesale, generic quadruple-therapy components assembled from individual prescriptions roughly $80–200. Insurance generally covers diagnostic testing and treatment when indications are clear. The whole episode — test, two-week course, follow-up test — typically wraps in 6–8 weeks.

When the standard course is a bad idea

A few other situations that change the regimen rather than cancelling it:

Severe kidney disease — bismuth and some antibiotic doses need adjustment.
Significant alcohol use — metronidazole plus alcohol causes a flushing, nauseating reaction (disulfiram-like). Stop drinking for the two weeks of treatment plus 48 hours after.
Prior antibiotic exposure — if you've taken clarithromycin or levofloxacin in the past for any reason (a chest infection, a tooth abscess), assume your strain is resistant to it and use a regimen built on different drugs.
Severe acid reflux or Barrett's oesophagus — eradication can restore normal acid output in some people, which occasionally worsens reflux symptoms. Worth discussing with a gastroenterologist before treating.
Bone-marrow problems or active eye inflammation — relevant if a rifabutin-based regimen is on the table.

Drug interactions worth flagging: acid-suppressing pills can blunt the antiplatelet effect of clopidogrel; rifabutin (in the alternative triple regimen) speeds up the breakdown of oral contraceptives and several HIV medications. Tell the prescriber every drug you take.

Old beliefs worth dropping

"Ulcers are caused by stress and spicy food." They aren't. They're caused by this bacterium and by long-term anti-inflammatory pills like ibuprofen. The doctors who proved it — Barry Marshall and Robin Warren — got the Nobel Prize in 2005, but the old framing still survives in casual conversation a generation later Sugano et al., Gut 2015.

"If I don't have symptoms, I don't have a problem." Chronic gastritis is universal in everyone infected, symptoms or not Sugano et al., Gut 2015. The cancer staircase climbs silently for decades. Symptoms are not a reliable signal — most infected people will feel nothing right up until they get an ulcer or a cancer diagnosis.

"The home blood-antibody kit told me I'm fine." Antibodies tell you whether you have ever been infected, not whether you are infected now. They stay positive for years after eradication and they go positive in past infections that have already cleared. Use the breath test or the stool antigen for an active-infection answer Best et al., Cochrane 2018.

"Probiotics or natural remedies clear it." They don't. Some probiotics modestly reduce the side effects of antibiotic therapy, but no diet, herb, or supplement reliably eradicates H. pylori. Mastic gum, broccoli sprouts, and manuka honey have small studies; none reach the eradication rates needed to count as treatment.

Why eradication sometimes fails

About 10–20% of first attempts don't work, and the two reasons are almost always the same: antibiotic resistance and missed doses.

Resistance is the bigger of the two now. Decades of treating other infections with the same antibiotics — clarithromycin for chest infections, levofloxacin for urinary infections, metronidazole for dental work — selected for H. pylori strains that resist them. Roughly one in three strains worldwide is now clarithromycin-resistant, well past the 15% threshold at which empiric clarithromycin-based therapy stops working Hu et al., Ann Clin Microbiol Antimicrob 2023. This is why the 2024 American guideline moved the older clarithromycin triple out of first-line and put bismuth quadruple therapy in its place Chey et al., ACG Guideline 2024.

Compliance is the second. A 14-day, four-drug, three-or-four-doses-a-day regimen is unpleasant. The most common failure pattern is to feel fine by day five, get tired of the schedule, and trail off — leaving a smaller population of resistant bugs to repopulate the stomach. Take every pill.

If the first course fails, the rule is: don't reuse the antibiotics that just failed. The second course swaps in different drugs (commonly levofloxacin-based, or bismuth quadruple if you started with vonoprazan). A third course, if needed, ideally tests your strain's susceptibility profile first.

One last failure mode worth naming: reinfection. In adults in high-income countries this is rare — under 2% per year Maastricht VI Consensus, Gut 2022. A "positive test six months later" almost always means the first course didn't fully clear the bug, not that you caught it again.

What changes once it's gone

If you had symptoms — ulcer pain, gnawing dyspepsia, the recurring 2 a.m. wake-up — the change inside the first month is the kind that makes people text the friend who told them to get tested. The lining stops being chronically inflamed; the ulcer heals on the acid-suppressing pill the regimen already includes. A year later, ulcers come back in under one in ten people post-eradication, versus the majority on acid-suppression alone Chey et al., ACG Guideline 2024.

If the bug had been quietly draining your iron, the felt change comes more slowly. With iron supplementation added on, ferritin and haemoglobin climb over months Muhsen & Cohen, Helicobacter 2008. The colleague who was always a little tired and a little pale stops being either. If B₁₂ was low and atrophy hasn't yet hardened in, replacement plus eradication restores levels, and the foggy thinking lifts Lahner et al., World J Gastroenterol 2018.

If you were asymptomatic to begin with, the felt change is invisible — and the benefit is real anyway. Over the next two or three decades, your stomach lining stops accumulating the damage that leads to cancer. The cancer-risk curve drops by roughly a third in the average infected adult, and by more than half if you started from the high-risk group of first-degree relatives of stomach cancer patients Ford et al., Cochrane 2020 Choi et al., NEJM 2020. You will never know whether you were the person whose cancer didn't happen. That's the deal you took.

And once it's gone, it stays gone. Adult reinfection in places with safe water and basic sanitation is rare enough that the test-of-cure result is, for practical purposes, the end of the story Maastricht VI Consensus, Gut 2022.

A few related topics worth knowing about: gastric cancer screening with periodic endoscopy is recommended in some high-prevalence countries (Japan, Korea) and selectively elsewhere — eradication is complementary, not a substitute. Long-term NSAID and aspirin use share the ulcer-and-bleeding mechanism with H. pylori; the risk multiplies when both are present. Vitamin B₁₂ and iron testing is worth knowing about in its own right when fatigue, pallor, or cognitive complaints don't track to an obvious cause. Proton-pump inhibitors are part of the eradication regimen and a separate topic in their own right when used long-term.

Related in the handbook

— Clearing the bug takes two weeks of multiple antibiotics — worth pairing with a plan to help your gut bacteria recover afterward.
— Chronic stomach inflammation from this bug also leaks B12 — another reason to clear it.
— If your ferritin is low for no clear reason, H. pylori belongs on the list of causes.
— This bug quietly drains iron for years — clearing it can fix a deficiency nobody could explain.
— PPIs are part of the two-week clearance regimen, but long-term they're a separate decision.

Substance and claimed effects

Helicobacter pylori is a gram-negative, spiral-shaped, microaerophilic bacterium that colonises the gastric mucosa, typically acquired in early childhood and persisting lifelong without treatment Kao 2016. Pooled global prevalence in adults is roughly 43.9% (2015–2022), down from 52.6% before 1990; childhood/adolescent prevalence is ~35.1% Li 2024. Earlier estimates from Hooi 2017 put the global infected population at ~4.4 billion in 2015, with Africa highest (~70%) and Oceania/Northern Europe lowest (~20–25%). The claimed and demonstrated consequences within scope of this entry: chronic active gastritis in essentially 100% of infected hosts Sugano 2015; peptic ulcer disease (gastric and duodenal) in roughly 10–15% of infected hosts over a lifetime; non-cardia gastric adenocarcinoma (IARC Group 1 carcinogen since 1994, ~89% population-attributable fraction worldwide) IARC 1994 Plummer 2015; gastric MALT lymphoma; iron-deficiency anaemia (especially unexplained / refractory) Muhsen 2008; vitamin B₁₂ malabsorption via parietal-cell loss and atrophic gastritis Lahner 2018; and immune-mediated effects (e.g., idiopathic thrombocytopaenic purpura). Eradication is curative; reinfection in adults from high-income countries runs <2% per year. The entry treats H. pylori as a single substance whose meta scores reflect every meaningful consequence above.

Evidence by addressing question

mechanism

H. pylori survives gastric acid by secreting urease, which hydrolyses urea to ammonia and bicarbonate, neutralising its local microenvironment well enough to traverse the mucus layer Kao 2016. Polar flagella drive chemotaxis toward the gastric epithelium, where adhesins (BabA, SabA, OipA) bind Lewis-b and sialyl-Lewis-x antigens on gastric epithelial cells, anchoring lifelong colonisation. Two effector molecules drive most of the pathology: CagA, a ~140-kDa oncoprotein delivered into the host cell through a type IV secretion system encoded on the cag pathogenicity island, is tyrosine-phosphorylated at EPIYA motifs by host Src-family kinases and rewires SHP-2 signalling, cell polarity, junctional integrity, and proliferation — CagA-positive strains carry roughly 1.7–2.0-fold elevated gastric-cancer risk vs CagA-negative Kao 2016. VacA (vacuolating cytotoxin A) forms anion-selective channels in epithelial membranes, induces vacuolation, mitochondrial dysfunction, and impairs T-cell activation, contributing to immune evasion. The chronic inflammatory response (predominantly Th1/Th17, IL-8 driven) plus direct DNA damage from reactive oxygen and nitrogen species progresses through the Correa cascade — chronic active gastritis → atrophic gastritis → intestinal metaplasia → dysplasia → invasive adenocarcinoma — over decades Sugano 2015. The same atrophic process destroys parietal cells (acid + intrinsic factor) and the iron-handling machinery, which is why iron and B₁₂ deficiencies are downstream of the same biology that drives cancer risk Lahner 2018.

evidence — gastritis and peptic ulcer

Histological gastritis is present in essentially every infected individual on biopsy; symptoms vary widely Sugano 2015. The Kyoto consensus reclassified H. pylori gastritis as an infectious disease in its own right — i.e., the recommendation is to treat the infection whether or not symptoms are present, except where competing risks dominate. Peptic ulcer disease: before NSAIDs displaced it as a leading cause in high-income settings, H. pylori was responsible for ~90% of duodenal ulcers and ~70–80% of gastric ulcers; the bug-NSAID mix now varies by population, but in the 2024 ACG guideline H. pylori remains the leading or co-leading etiology and every active PUD patient should be tested Chey 2024. Eradication reduces ulcer recurrence from ~60–80%/year (on antisecretory monotherapy) to under 10%/year — among the largest treatment effects in gastroenterology.

evidence — gastric cancer

IARC classified H. pylori as a Group 1 (definite) human carcinogen in 1994 IARC 1994, and the global-burden estimate attributes 89% of non-cardia gastric adenocarcinoma worldwide to H. pylori — roughly 660,000 cases per year, ~5.2% of all cancers globally Plummer 2015. The Cochrane meta-analysis of RCTs in asymptomatic infected adults found eradication reduces incident gastric cancer with a relative-risk pooled estimate around 0.54 (95% CI ~0.40–0.72), with a ~36% reduction in incidence and ~22% reduction in mortality Ford 2020. Two landmark trials anchor the strongest evidence: Choi 2018 (NEJM, n=470) randomised patients after endoscopic resection of early gastric cancer to eradication vs placebo and found metachronous cancer in 7.2% vs 13.4% (HR ~0.50) plus regression of corpus glandular atrophy. Choi 2020 (NEJM, n=1,676) randomised first-degree relatives of gastric cancer patients to triple therapy vs placebo and found a 55% reduction in incident gastric cancer with intention-to-treat; among those with confirmed eradication, the reduction reached 73%. Korean nationwide cohort data extend the benefit to people aged ≥70. The window for benefit is widest before atrophy/metaplasia develop, but reduction persists even after the point of no return — just smaller.

evidence — MALT lymphoma

Gastric mucosa-associated lymphoid-tissue (MALT) lymphoma is one of the few human malignancies curable with antibiotics. Pooled remission after H. pylori eradication alone is 77.5% (95% CI 75.3–79.7) across 32 studies and 1,408 patients; stage IE 78.4% vs IIE 55.6%; distal vs proximal stomach 91.8% vs 75.7%; mucosa-confined vs deeper invasion 82.2% vs 54.5%; relapse ~2.2% per year Zullo 2010. The t(11;18)(q21;q21) API2–MALT1 translocation predicts non-response. Eradication is the first-line treatment for early-stage gastric MALT lymphoma in every modern guideline.

evidence — iron and B₁₂ absorption

The Muhsen-Cohen meta-analysis found pooled OR ~2.22 (95% CI 1.52–3.24) for iron-deficiency anaemia and ~1.38 for iron deficiency among H. pylori-infected vs uninfected adults Muhsen 2008. Mechanisms: bacterial iron sequestration (H. pylori expresses ferritin and iron-uptake systems), reduced ascorbate in gastric juice (impairs non-heme iron reduction), hypochlorhydria from atrophic gastritis (reduces ionisation), and hepcidin-mediated iron sequestration from chronic inflammation. The Maastricht VI consensus recommends H. pylori testing/treatment in unexplained iron-deficiency anaemia after standard GI work-up Maastricht VI 2022. For B₁₂: atrophic body gastritis destroys parietal cells, eliminating intrinsic factor and acid; without intrinsic factor, dietary B₁₂ cannot be absorbed in the terminal ileum, leading to macrocytic anaemia and, untreated, subacute combined degeneration of the cord Lahner 2018. Eradication can reverse pathology and improve B₁₂ status in a subset of patients before atrophy is fixed. ACG 2024 lists unexplained IDA and unexplained B₁₂ deficiency among indications to test for H. pylori Chey 2024.

protocol

The 2024 ACG guideline reorganised first-line therapy in response to global clarithromycin resistance (pooled ~33%, well above the 15% threshold at which empiric clarithromycin-based triple therapy fails) Hu 2023 Chey 2024. Recommended first-line options (all 14 days unless noted):

Optimised bismuth quadruple therapy (BQT) — PPI (standard or double-dose) + bismuth subcitrate/subsalicylate + tetracycline 500 mg QID + metronidazole 500 mg TID/QID. Eradication ~85–95% irrespective of clarithromycin resistance. Preferred first-line in nearly all settings.
Rifabutin triple therapy (PAR: omeprazole + amoxicillin + rifabutin, FDA-approved as Talicia). Useful where bismuth is poorly tolerated.
Vonoprazan dual therapy (vonoprazan + amoxicillin) and vonoprazan triple therapy (+ clarithromycin) — based on PHALCON-HP (n=1,046), vonoprazan triple 84.7% vs lansoprazole triple 78.8% in non-resistant strains; in clarithromycin-resistant strains vonoprazan triple/dual hit ~66–70% vs lansoprazole 32% Chey 2022. Vonoprazan-amoxicillin dual is appealing where clarithromycin resistance is high or unknown.
Legacy clarithromycin-based triple (PAC) — no longer recommended empirically unless local clarithromycin resistance is <15% and the patient has had no prior macrolide exposure.

Test-of-cure (urea breath test or stool antigen) is mandatory ≥4 weeks after completing therapy and ≥2 weeks after stopping PPI, since both classes can produce false-negative results Maastricht VI 2022. First-line failure salvage: avoid antibiotics already used; second-line typically BQT (if not first line) or levofloxacin-based triple; third-line susceptibility-guided where possible.

contraindications

Tetracycline contraindicated in pregnancy and children <8 years; metronidazole avoid with alcohol; bismuth may colour stools/tongue black, contraindicated in significant renal impairment; rifabutin causes orange discoloration of body fluids and rare bone-marrow suppression. Vonoprazan and PPIs have the usual long-term concerns when used chronically (not relevant for 14-day courses). Drug interactions to flag: PPI/vonoprazan with clopidogrel, rifabutin's CYP3A4 induction (oral contraceptives, antiretrovirals). For patients with severe GERD or Barrett's, balance: eradication restores acid output in many, which can worsen reflux symptoms Sugano 2015.

misconceptions

Three persistent myths. First, that stress and spicy food cause peptic ulcers — they don't; H. pylori (and NSAIDs) do, and this was the Marshall/Warren Nobel discovery Sugano 2015. Second, that asymptomatic infection is harmless — chronic gastritis is universal in infected hosts, and downstream cancer risk accrues silently Sugano 2015. Third, that serology suffices for diagnosis — IgG antibodies persist for years after eradication and cannot distinguish active from past infection; urea breath test (sensitivity ~94% at fixed specificity 0.90) or monoclonal stool antigen (~83%) are the active-infection tests Best 2018. Serology is acceptable only for prevalence studies or specific clinical contexts (recent bleeding, recent antibiotic/PPI use that limits active testing).

practicalities

In the US: stool antigen $50–150 cash; urea breath test $100–300; endoscopy with biopsy $1,500–3,000. Most insurance covers diagnostic testing when indicated. Voquezna Triple Pak (vonoprazan + amoxicillin + clarithromycin) wholesale ~$650 for 14-day course; Pylera (bismuth/metronidazole/tetracycline + separate PPI) ~$700–900; generic BQT components assembled from individual prescriptions ~$80–200. Compliance is the dominant determinant of eradication success — 4-drug 14-day regimens with multiple daily doses pose real adherence challenges; failure on a first-line regimen worsens the resistance picture for any future attempt.

audience and population variability

Highest infection prevalence and gastric cancer incidence: East Asia (Japan, Korea, China — >95% of gastric cancer attributable to H. pylori), Andean Latin America, parts of Eastern Europe, sub-Saharan Africa. Lowest: Northern Europe, Australia, North America (US adult prevalence ~30–35%). First-degree relatives of gastric cancer patients carry roughly 2–3× the baseline gastric-cancer risk, and eradication produces the largest absolute risk reduction in this group Choi 2020. Immigrants from high-prevalence regions retain elevated risk for life. Children acquire most infections within the family (mother-child) and population-wide screen-and-treat is the framework where prevalence justifies it (Matsu Islands, Bhutan, Japan's national insurance coverage).

stakes

Untreated active infection means progressive chronic inflammation of the stomach lining over decades. In the typical infected adult, the 10–20-year picture: ~10% lifetime risk of peptic ulcer, ~1–3% lifetime risk of non-cardia gastric cancer (substantially higher in East Asians, first-degree relatives, and those with established atrophy/metaplasia), risk of MALT lymphoma, and a meaningful elevation in unexplained iron-deficiency anaemia and B₁₂ deficiency that often presents as fatigue or cognitive complaints attributed to other causes. Cancer is the dominant late risk: 89% population-attributable fraction, ~660,000 H. pylori-attributable cancer cases per year globally Plummer 2015.

payoff

Successful eradication: ulcer recurrence drops from majority-per-year to single digits; non-cardia gastric cancer risk cut by ~36% on average Ford 2020, by 55–73% in first-degree relatives of cancer patients Choi 2020, ~46% in the metachronous-cancer setting Choi 2018; ~77% remission of stage I gastric MALT lymphoma Zullo 2010. Iron stores and ferritin improve when eradication is paired with iron supplementation; B₁₂ may improve in patients without fixed atrophy Lahner 2018. Felt effects: in symptomatic carriers (dyspepsia, ulcer pain), the symptomatic improvement at 4–8 weeks is often dramatic. In asymptomatic carriers, the felt effect is invisible — the benefit is a probability distribution that shifts down over years and decades. Reinfection rate in high-income adult populations <2%/year — eradication is essentially permanent.

The credibility range

Optimist case. H. pylori is one of the few infectious diseases that causes a major human cancer, and we can cure it with two weeks of antibiotics. RCT evidence for cancer prevention is rare in oncology and we have it here — Cochrane RR ~0.54, Choi 2020 hazard reduction 55%, Choi 2018 46% in the highest-risk metachronous setting. Population screen-and-treat in high-prevalence regions could prevent hundreds of thousands of cancer deaths per year. In first-degree relatives, the case for active testing is borderline mandatory. Even ignoring cancer, the bug causes universal gastritis, the lion's share of peptic ulcers, and meaningful nutritional consequences (iron, B₁₂). The 2024 ACG and 2022 Maastricht VI consensus both have strong, mature guideline statements.

Skeptic case. Most infected people never develop ulcer or cancer — the population-attributable fraction is high because gastric cancer is common, not because per-person risk is large in low-incidence populations. Cochrane's only non-Asian trial showed no benefit Ford 2020; extrapolating Korean/Chinese cancer-prevention effect sizes to low-prevalence Western settings is uncertain. Eradication has real downsides: rising clarithromycin/levofloxacin/metronidazole resistance from antibiotic pressure Hu 2023, gut-microbiome disruption from 14-day quadruple therapy, post-eradication GERD/Barrett's risk via restored acid output, possible inverse association with childhood asthma/allergy (interpretation contested). For asymptomatic adults with no family history in a low-incidence region, the number needed to treat for cancer prevention is large.

Author's call. Test and treat whenever H. pylori is found incidentally and in every guideline-indicated scenario (active or past PUD, MALT lymphoma, unexplained iron/B₁₂ deficiency, after endoscopic resection of early gastric cancer, first-degree relatives of gastric cancer patients, long-term NSAID or low-dose aspirin starters at elevated risk, planned long-term PPI use). For asymptomatic adults without these indications, the case is real but weaker outside high-prevalence populations; offer testing on request, especially for immigrants from high-prevalence regions and people with strong family history beyond first-degree. Use bismuth quadruple therapy or vonoprazan-based regimens first-line; do not use empiric clarithromycin triple. Always perform test-of-cure. The intervention is high-evidence, high-impact when targeted, and one of the genuinely settled wins in modern gastroenterology — controversy is around how broadly to screen, not whether eradication works.

Stakeholder and incentive map

Gastroenterology societies (ACG, AGA, ESGE, JSGE, KSGE) push for guideline-directed test-and-treat. ACG 2024 represents a major rewrite away from clarithromycin-based triple Chey 2024.
Pharmaceutical interest in vonoprazan (Phathom Pharmaceuticals' Voquezna brands) is real and shapes the visibility of PCAB-based regimens in the US.
WHO / IARC push for population screen-and-treat in high-incidence regions; the 2025 IARC working-group NEJM brief makes this explicit.
National screening programmes: Japan covers eradication therapy under national insurance for all infected adults since 2013; Korea recommends in first-degree relatives; Matsu Islands and Bhutan run population programs.
Primary care / generalist resistance to testing asymptomatic adults persists, partly from older "no symptoms, no treatment" framing.
Antibiotic stewardship advocates push back against broad population eradication on resistance grounds, especially with multi-drug 14-day regimens.

Population variability

Per-person consequence depends heavily on host factors (East Asian and indigenous Andean genetics, IL-1B/IL-1RN polymorphisms), strain factors (cagA+, vacA s1/m1, babA2 all elevate cancer risk), age at acquisition (childhood acquisition + decades of inflammation = higher cancer risk), co-factors (high-salt diet, smoking, low fruit/vegetable intake), and stage at diagnosis (atrophy/metaplasia are partial points of no return). Within any infected population the distribution of outcomes is skewed: most never develop ulcer or cancer; a meaningful minority do, and the cancer minority bears outsized disease burden. First-degree relatives of gastric-cancer patients are the population where evidence and absolute risk reduction align most tightly Choi 2020.

Knowledge gaps

Whether eradication after established atrophy/metaplasia reduces cancer risk to baseline or only halts further progression — current best estimate is partial reduction, full reset unlikely.
The optimal age window for population screening — childhood vs young adulthood vs middle age.
Whether reducing childhood infection prevalence (sanitation, family hygiene) is more cost-effective than adult screen-and-treat.
The microbiome cost of 14-day quadruple regimens, and whether targeted/short courses preserve efficacy.
Whether putative inverse associations with asthma, GERD/Barrett's, obesity reflect real causal protection or epidemiological confounding; H. pylori's "good cholesterol" framing is overplayed but the question remains open.
Generalisability of Asian cancer-prevention trials to low-prevalence Western populations.
Long-term vonoprazan safety relative to PPIs at scale; PHALCON-HP was 14 days.

Scope vs brief. The brief named gastritis, peptic ulcer disease, iron and B₁₂ absorption, gastric cancer risk, and eradication regimens. All five are covered end-to-end. Gastric MALT lymphoma was added because the eradication evidence is unusually strong (~77% remission with antibiotics alone) and it gives the cancer story a second pillar.

Action / cadence call. Set to decide rather than do because the right move depends on personal context — family history, symptoms, geography, prior antibiotic exposure — and a clinician is required (prescription-only multi-drug regimen with real interactions and contraindications). Cadence course is the natural fit: one bounded 14-day treatment plus test-of-cure, no recurring action.

Rating difficulties.

longevity: 4 rather than 5 — the cancer-prevention effect is large and rare in oncology, but it bites hardest in high-prevalence populations and in first-degree relatives. Pooled relative reduction (~36% Cochrane) is real but the absolute number-needed-to-treat in a low-prevalence Western adult is high. A 5 would imply a population-level mortality shift on the order of smoking cessation, which this isn't outside East Asia.
health_short_term: 3 is dominated by the symptomatic-carrier subgroup (ulcer, dyspepsia). For asymptomatic carriers — the majority — short-term felt change is near zero. The 3 is honest on the population that actually feels it.
energy / focus / mood at 1–2 reflect the iron and B₁₂ pathway, which is real but narrow — a meaningful minority. Not putting these at 0 would have been the easier call; including them honours the "score holistically across the substance" rule.
beauty_cumulative: 1 via iron-deficiency anaemia is genuinely a stretch; the indirect path is plausible but the literature is not specifically aesthetic. Considered scoring 0; left at 1 because the iron/anaemia pathway is documented (Muhsen 2008) and the friend test for the cumulative-beauty card pitch passes.
controversy: 2 — debate is about screening breadth and antibiotic-stewardship trade-offs, not about whether the bug causes disease or whether eradication works. Going higher would overstate the disagreement.

Separate-entry candidates.

Peptic ulcer disease — substantial enough to deserve its own entry, with H. pylori as one of two etiologies (NSAIDs the other).
Gastric cancer screening — population-level endoscopic screening as practised in Japan and Korea is its own topic, complementary to eradication.
Proton-pump inhibitors (long-term use) — referenced here as part of the regimen, but the long-term safety / deprescribing question is a separate substance.
Vonoprazan and the PCAB class — pharmacology that touches H. pylori, GERD, and PUD; worth a dedicated entry as adoption grows outside the US.

Future links. Once they exist: peptic-ulcer-disease, gastric-cancer-screening, ppi-long-term, ferritin-testing, b12-deficiency, nsaid-risk. Left related empty rather than guess ids.

Excluded.

Putative protective associations with asthma, GERD, Barrett's, obesity — left in the research dossier's credibility range but kept out of the article. The evidence is mostly epidemiological with confounding, and an "H. pylori may protect against asthma" line in reader-facing prose would be irresponsible given the cancer story.
Idiopathic thrombocytopaenic purpura (ITP) and H. pylori — real association but a niche haematology indication, not catalogue-relevant for a generalist audience.
Pediatric guidelines (ESPGHAN/NASPGHAN 2024) — adult-focused entry; pediatric eradication is a separate clinical context.
Detailed antibiotic-resistance maps by country — too operational for the reader; named the headline (clarithromycin ~33% globally) and the practical consequence (don't use empiric clarithromycin triple) instead.

Contraindication token. Used only pregnancy from the closed vocabulary. Tetracycline (in the standard quadruple) is the hard contraindication; breastfeeding is mostly compatible with regimen modification. The closed vocabulary did not include obvious tokens for severe renal disease, alcohol use, or prior macrolide exposure — those are surfaced in the article's contraindications section as regimen-modifying rather than entry-blocking.