We don’t know what causes most stomach cancers. But there are some factors that may increase your risk of developing it.
Having any of these risk factors does not mean that you will definitely develop cancer.
Fruit and vegetables
Eating too few fruits and vegetables can increase your risk of getting stomach cancer. Try to have at least 5 portions of fruit and vegetables every day.
Eating foods that are high in salt can increase your risk of stomach cancer. It causes around 1 in 4 stomach cancers.
Try not to eat too much salty food. Adults should aim to have no more than 6g of salt a day. This is around one teaspoon. In the UK, most people eat more than this. Most of the salt we eat is in the everyday foods such as bread, cereals and ready meals.
Your risk of stomach cancer also increases if you eat lots of pickled vegetables.
There is some research linking stomach cancer to eating a diet that is high in processed meat. Processed meat includes ham, bacon, salami and sausages.
The government recommends that people eating more than 90g of red and processed meat a day should reduce it to 70g or less (cooked weight). This is about the same as about 2 sausages.
Smoking tobacco increases your risk of getting stomach cancer. Around 1 in 5 of stomach cancers in the UK is linked to smoking. Your risk increases with the number of cigarettes smoked a day.
It is never too late to stop smoking but the sooner you stop the better.
Being overweight or obese
There is some research linking being overweight or obese to stomach cancer, however the evidence isn’t certain. Obesity means being very overweight with a body mass index (BMI) of 30 or higher. A BMI between 25 and 30 is overweight.
Try to keep a healthy weight by being physically active and eating a healthy, balanced diet.
Helicobacter pylori infection
Infection with Helicobacter pylori (H.pylori) causes around 1 in 3 stomach cancers.
H. pylori is a bacteria that live in the mucous of the lining of the stomach. For most people, having a H. pylori infection will not cause any problems. But in some cases long term infection can cause inflammation and stomach ulcers.
About 4 out of 10 people in the UK (40%) have this infection and most people who have it don’t develop stomach cancer.
There is also some evidence that diet and smoking may interact with H. pylori to increase the risk of stomach cancer.
Blood, stool and breath tests can find Helicobacter infection. The treatment is a course of antibiotics with a medicine to reduce the amount of acid in your stomach.
Other factors that affect your risk
Age and sex
Stomach cancer is more common in older people. Around half of stomach cancers develop in people aged 75 or over. Men are nearly twice as likely to get the disease compared to women.
Low amounts of stomach acid
Your risk of stomach cancer is higher if you have a condition that lowers the amount of acid in the stomach or if you’ve had an operation on your stomach that reduces the amount you produce.
Having a reduced immune system increases your risk of stomach cancer. Reduced immunity means that you are prone to picking up infections. The increase in risk is probably because of the increase in risk of picking up Helicobacter pylori.
Some medical conditions and treatments can reduce your immune system by suppressing it. This includes HIV, Aids, pernicious anaemia and treatment after an organ transplant.
Some occupations and working with particular chemicals can increase your risk of stomach cancer. For example working in the rubber production industry.
There is also some research linking exposure to asbestos and inorganic lead compounds to stomach cancer, however this evidence is limited.
Exposure to these kinds of chemicals at work is rare and there are regulations to protect people at work.
Your risk of stomach cancer is 2 to 10 times higher if you have a family history of the disease. It isn’t clear why this is but it may be to do with sharing other risk factors.
Some people inherit genes that can increase their chance of stomach cancer, for example a change in the E-Cadherin (CDH1) gene.
Radiotherapy for other cancers slightly increase your risk of stomach cancer, including:
- testicular cancer
- cervical cancer
- breast cancer
- head and neck cancers
Your risk of getting stomach cancer is still small. You would be at a much higher risk from the cancer you’re having radiotherapy for if you don’t have it.
Reducing your risk and other possible causes
You might have heard of other possible causes of cancer. Stories about potential causes are often in the media and it isn’t always clear which ideas are supported by evidence.
We haven’t included them here, either because there is no evidence about them or it is less clear.