The short answer
Stomach cancer is more common in Japan and East Asia than in the United States. A major driver is infection with H. pylori bacteria, along with high-salt diets and smoking.
Stomach cancer is the main cancer that is more common in Japan than in most of the world.
The leading cause is infection with H. pylori, a common stomach bacteria.
Diets high in salt-preserved foods and smoking also raise the risk.
Changing these risk factors, such as treating H. pylori, eating less salt and not smoking, can lower risk.
Choose how you want to read this
The whole article, with every detail and caution.
This page is for anyone curious about why stomach cancer is so common in Japan, and what that means for their own risk.
The simple answer
Stomach cancer is Japan's big exception. Stomach cancer is much more common in East Asia, including Japan, than in the United States. A common stomach bacterium called H. pylori is a major cause, and a high-salt diet and smoking also raise risk.
The main driver: H. pylori
The single most important cause of stomach cancer in Japan is infection with H. pylori. This is a type of bacteria that can live in the lining of the stomach. It is very common around the world, and many people carry it without ever feeling sick.
Over many years, though, H. pylori can cause ongoing inflammation of the stomach lining, called gastritis. In some people, this slow damage can eventually lead to stomach cancer. NCI says there is consistent evidence that chronic H. pylori infection causes the most common type of stomach cancer.
NCI reports that in a major study, treating the infection with antibiotics was linked to a lower rate of stomach cancer over 15 years. Ask your care team whether testing makes sense for you.
Salt-preserved foods
Diet also plays a role. For much of Japan's history, before refrigeration was common, people preserved food with large amounts of salt — think salted fish and heavily pickled vegetables.
NCI says excessive salt intake, and too few fresh fruits and vegetables, are associated with higher stomach cancer risk.
Smoking adds to the risk
Smoking is another contributor. NCI reports about a 60% higher risk of stomach cancer in male smokers and a 20% higher risk in female smokers compared with nonsmokers, and risk falls over time in former smokers.
What can lower risk
The hopeful part of the story is that several risk factors can be changed: treating H. pylori infection, eating less salt and more fresh fruits and vegetables, and not smoking. Stomach cancer is not simply "in the genes" of a country. It responds to infection, diet, and habits.
The role of screening
In high-risk regions such as Japan, screening programs that use endoscopy, in which a doctor uses a thin camera to look inside the stomach, have contributed to earlier detection, according to NCI. NCI also states that there is no standard screening test for stomach cancer in the United States. Whether screening makes sense for you is a question for your care team.
Who is at higher risk
Not everyone faces the same stomach cancer risk. Risk is higher in:
- people who carry H. pylori
- people with a family history of stomach cancer
- older adults
- people who smoke
- people who eat a lot of salt-preserved food
If several of these apply to you, ask your doctor whether testing for H. pylori or extra monitoring makes sense. This is not a cause for alarm, just a sensible personal step.
What this means for you
If you live outside Japan, stomach cancer may be less common where you are, but the lessons still apply. If you have stomach symptoms that do not go away, such as ongoing pain or indigestion, see a doctor. Ask whether testing for H. pylori makes sense for you, especially if you have a family history of stomach cancer or come from a region where it is common.
Not smoking and going easy on very salty, heavily preserved foods are sensible steps for many reasons, including this one. As always, your own risk depends on your history, so talk with your care team about what fits you.
Sources
- National Cancer Center Japan — Cancer Statistics in Japan 2025
- IARC Monographs Volume 100B — Helicobacter pylori
- National Cancer Institute — Stomach (Gastric) Cancer
- National Cancer Institute — Helicobacter pylori (H. pylori) and Cancer
- National Cancer Institute — Stomach (Gastric) Cancer Prevention (PDQ)
Before you go
This article is for education only and is not a substitute for medical advice. Talk with a healthcare professional about your personal cancer risk, symptoms, screening, or treatment options.
We believe patients and families deserve cancer information that is calm, honest, and easy to read. If this was helpful, you might consider supporting Cancer Explained so we can keep this education free for everyone. There is no pressure — reading and sharing helps too.
Common questions
Why is stomach cancer more common in Japan?
The biggest reason is infection with H. pylori, a common stomach bacteria that can cause long-term inflammation. Past diets high in salt-preserved foods and smoking added to the risk. These are major factors in regions where stomach cancer is more common.
What is H. pylori?
H. pylori is a type of bacteria that can live in the stomach lining. It is very common worldwide and often causes no symptoms, but over many years it can lead to inflammation, ulcers, and, in some people, stomach cancer.
Can H. pylori be treated?
Yes. H. pylori infection is treated with antibiotics. NCI reports that in a major study, short-term treatment was linked to a lower rate of stomach cancer over 15 years. Ask your care team whether testing makes sense for you.
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
Tap a question to save it to your list (kept on this device).
Talk with a trained specialist or navigator
Cancer Explained provides educational guidance, but does not replace trained specialists, social workers, or your medical team.
Talk to a trained cancer information specialist
Free, confidential assistance from NCI Cancer Information Service via phone, chat, or email.
Contact your oncology team
Locate after-hours contact numbers, portal messages, or urgent triage phone lines.
Find a patient navigator
Get one-on-one help with appointments, logistics, translation, and care coordination.
Find a genetic counselor
Discuss inherited mutation risk, family history, and genetic testing options.
Find an oncology social worker
Access emotional counseling, family support groups, and mental health resources.
Find a financial navigator
Locate copay assistance foundations, grant programs, and lodging/travel support.
Find a clinical-trial specialist
Search matching studies and speak with NCI trial information specialists.
Get urgent help
Fever of 100.4°F (38°C) or higher during chemo, severe pain, or trouble breathing: call your cancer care team right away, day or night. Call 911 for an emergency.
Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Sources last checked: 2026-10-01 what this meansLast updated: 2026-10-16Next planned review: 2027-07-08
Review details and limits
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status — Source checked. This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
General education — varies by person. Answers genuinely differ between people. This page explains what commonly varies and points you to your care team for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
Words to know
Tap any term to see what it means.
Knowledge check
0 of 4 answered
This self-assessment checks understanding of educational content only. It is not medical advice.
How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
Read more about our editorial process, our use of AI, and our corrections policy.
Spotted a problem? Report an error — a factual mistake, broken or outdated source, confusing wording, or anything that seems unsafe. Please do not include names, medical record numbers, dates of birth, addresses, or other identifying medical information in your report.
After using this page, do you understand what to do next?
Anonymous — we only record the answer, never who gave it.