Most people think of smoking or genetics as the main causes of cancer. It may be surprising to learn that bacteria can also play a role.
Scientists have discovered that some bacteria can live in the body for years and contribute to cancer. The main example is Helicobacter pylori, or H. pylori, a spiral-shaped bacterium found in the stomach that causes most cases of stomach cancer worldwide.
Understanding this link is not only about knowing your risk. It also helps you take steps to prevent problems. By learning how these bacteria work, you can make choices that protect your health in the long run.
The Bacterium Living in Your Stomach
Around half of all people have H. pylori, often getting it as children. Most never notice any symptoms, as the bacteria usually remain in the stomach without causing problems.
However, in some people, H. pylori causes ongoing inflammation in the stomach. This mild irritation can last for years without clear symptoms. Over time, it may lead to ulcers, changes in stomach cells, and, in a small number of cases, stomach cancer.
The numbers are significant:
- The World Health Organisation classifies H. pylori as a definite cause (Type I carcinogen) of stomach cancer.
- Around 90% of non-cardia gastric cancers worldwide are linked to H. pylori infection.
- A 2025 Nature Medicine study predicts 15.6 million stomach cancer cases among those born between 2008 and 2017, with 76% directly tied to H. pylori.
If this is the first time you are hearing about H. pylori, you are not alone. More people are learning about it, but many still do not know. Sharing this information is important.
How H. Pylori Leads to Cancer
Ongoing inflammation from H. pylori is similar to a wound that does not heal. The bacteria settle in the stomach lining and cause continuous inflammation, which is called gastritis.
Some strains of H. pylori produce a protein called CagA. This protein interferes with how your cells repair themselves. When cells can’t fix damage properly, DNA errors start to build up. In a small number of people, these errors can eventually lead to cancer.
This process happens slowly and without obvious signs. It can take many years, which is why stomach cancer often appears later in life. Finding H. pylori early gives you a chance to prevent serious problems.
What Raises Your Risk
Having H. pylori does not mean you will definitely get cancer. Your diet, surroundings, and daily habits all affect whether the bacteria cause health issues.
- High salt intake: Too much salt irritates your stomach lining, making it easier for damage to occur. Pickled and heavily salted foods increase this risk.
- Processed meats: Bacon, sausages, and deli meats contain nitrates that can form cancer-causing compounds in your stomach.
- Smoking: Tobacco chemicals roughly double your stomach cancer risk by directly harming stomach cells and weakening your immune response.
- Family history: Shared genes and household habits can make certain families more vulnerable to both H. pylori infection and stomach cancer.
- Geographic location: Rates are higher in East Asia, Latin America, and Eastern Europe, where H. pylori is more common and traditional diets tend to be salt-rich.
The good news is that you can control many of these factors. Adjusting your diet, stopping smoking, and having regular check-ups can all help lower your risk.
Treatment Can Prevent Cancer
A key finding in cancer prevention is that treating H. pylori is effective. Studies show that taking antibiotics for a short time, especially before any pre-cancerous changes develop, can greatly lower the risk of stomach cancer.
Treatment often involves taking antibiotics along with a medicine called a proton pump inhibitor (PPI) to lower stomach acid. This treatment usually lasts 10 to 14 days. Afterward, your doctor can check if the infection is gone with a follow-up test.
Some countries are trying out programs that screen people for H. pylori and treat those who test positive. Early results show these efforts can find infections and prevent stomach cancer from developing. In areas with higher risk, this approach has helped lower cancer rates.
If you have lasting stomach symptoms such as pain, bloating, or heartburn, or if stomach cancer is common in your family, ask your doctor about testing for H. pylori. Treating it early can help.
What About Other Bacteria?
Researchers are also looking at other bacteria that may be linked to different types of cancer. For example, some gut bacteria are connected to colon cancer risk, and bacteria in the mouth have been linked to mouth cancers.
However, H. pylori is currently the only bacterium that health organizations officially recognize as a definite cause of cancer. As research goes on, we will likely learn more about how gut bacteria affect disease.
Your gut does more than help with digestion. It is a complex system that affects your immune system, inflammation, and risk for disease. Looking after your gut is important.
Simple Steps to Protect Your Stomach
Even though H. pylori is common, you can take simple steps to keep your stomach healthy:
- Eat more fresh foods. Focus on fruits, vegetables, and whole grains. These foods contain antioxidants and fiber that support stomach health.
- Reduce salt intake. Limit pickled foods, heavily salted snacks, and processed meals. Fresh herbs and spices can add flavor without the salt.
- Cut back on processed meats. Choose fresh poultry, fish, or plant-based proteins instead of bacon, sausages, and deli meats.
- Quit smoking. Smoking greatly increases stomach cancer risk. Your GP can help with cessation support and resources.
- Get tested if you’re at risk. If you have ongoing stomach symptoms or a family history of stomach cancer, ask your doctor about H. pylori testing.
You do not have to make all these changes at once. Gradual improvements to your diet and habits can make a big difference over time and help lower your cancer risk.
Taking Control of Your Health
It may be surprising or even worrying to learn that bacteria can play a role in cancer. However, this knowledge also gives you the power to take action. You have more control over your health than you may realize.
Most people who have H. pylori do not develop stomach cancer. Still, being aware of the infection, knowing your risk factors, getting tested when needed, and treating it early can help protect your health.
Every day habits make a difference. Eating more fresh foods, reducing salt and processed meats, and quitting smoking all support better stomach health. Keeping in contact with your healthcare provider is important as well.
By staying informed and working with your doctor, you can take control of your health. Being aware is not about being afraid; it is about taking steps to prevent illness.
