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Stomach cancer risks and causes

Men and woman discussing stomach cancer

This page is about possible risk factors and causes for stomach cancer. Some factors may increase the risk, while others may lower it. There is information below about

 

A quick guide to what's on this page

Risks and causes of stomach cancer

There are almost twice as many cases of stomach cancer diagnosed in men as in women.

As with most cancers, cancer of the stomach becomes more common with increasing age. Around 95 out of 100 cases (95%) are diagnosed in people aged 55 or older.

A diet high in fresh fruit and vegetables seems to lower risk of stomach cancer. A diet high in preserved foods or very salty food increases risk.

Helicobacter pylori infection increases the risk of stomach cancer. But millions of people are infected with these bacteria and most of them do not get stomach cancer so there must also be other factors at work.

People who smoke have twice the risk of stomach cancer compared to non smokers.

 

CR PDF Icon You can view and print the quick guides for all the pages in the about stomach cancer section.

 

 

How common stomach cancer is

Stomach cancer is now the 15th most common cancer amongst adults in the UK. About 7,100 cases are diagnosed each year. Out of every 100 cancers diagnosed, 2 are cancer of the stomach (2%). Almost twice as many cases are diagnosed in men as in women.

 

Age

Like most cancers, stomach cancer becomes more common as people get older. Around 95 out of every 100 cases (95%) are diagnosed in people aged 55 or older. Our section about how a cancer starts explains why this is.

 

Diet

The incidence of stomach cancer in the UK has fallen a great deal since the 1970s. This is probably partly due to better diet.

Incidence varies from country to country around the world. This may be explained to some extent by differences in diet. A diet high in very salty foods increases the risk of stomach cancer. Stomach cancer levels are very high in Japan where very salty pickled foods are popular. But these foods are not typically eaten in the UK and stomach cancer rates here are lower than in Japan.

A diet high in certain preserved foods may also increase your risk. Several studies and a large ongoing research study called EPIC have found a small increase in the risk of stomach cancer in people who eat a lot of preserved meat. Preserved meat includes bacon, sausages and ham. These meats contain chemicals called nitrosamines, which have been linked to stomach cancer. A Canadian study found that the increased risk was greatest in people infected with Helicobacter pylori bacteria. Eating a lot of pickled foods may also increase the risk.

A recent study showed that vegetarians may have a lower risk of stomach cancer than meat eaters. And the EPIC study showed an increased risk of stomach cancer for people who eat a lot of red meat. But we need more studies to confirm this. 

A diet high in fresh fruit and vegetables seems to reduce the risk of stomach cancer. This may be because these foods contain high levels of antioxidant vitamins. Vitamin C in particular, together with other substances in these fresh foods, may help to prevent damage to the stomach lining that can lead to cancer. Vitamin A has been shown to protect against stomach cancer. One study has also suggested that vitamin B6 may have a protective effect. Research studies have shown that antioxidant vitamins may have the greatest protective effect in people who are under nourished. Antioxident vitamins help in well nourished people too, but their effects are likely to be less. This may explain why some recent studies in America and Europe found no association between fruit and vegetable intake and stomach cancer risk.

In the UK only about 1 in 3 adults eat enough fruit and vegetables - the recommended minimum of 5 portions a day. So there is a lot we can do to eat our way to a healthier life. If you are worried about cancer or heart disease, you could take a look at your diet and see if you can improve it. You'll find some tips in the healthy eating section of our News and Resources website.

 

Helicobacter pylori infection

Helicobacter pylori is a bacterial infection that has been investigated a lot in the past few years. Infection with this type of bacteria increases the risk of stomach cancer in the lower part of the stomach by around 6 times. Infection with a particular type of HP called cagA positive helicobacter pylori may increase the risk even more.

Millions of people are infected with these bacteria and most of those do not get stomach cancer so other factors must also be at work. Diet and smoking may interact with HP to cause stomach cancer. The bacteria can cause an inflammatory condition called severe chronic atrophic gastritis (SCAG) and this can lead to stomach cancer. People with SCAG have an increased risk of stomach cancer in both the upper and lower parts of the stomach.

Helicobacter infection can be shown on a blood test or a breath test. It can usually be cured fairly easily with a course of antibiotic treatment. But we're not really sure yet how much benefit we get from getting rid of it. HP may protect against a particular type of cancer of the food pipe (oesophagus) called adenocarcinoma of the oesophagus. A meta analysis of studies looking at HP treatment showed that it lowered the risk of stomach cancer a little bit but it may be most effective in people with peptic ulcer or pre cancerous changes. Even if you do have it treated, there is a chance that you will get re infected because it is so common. So your doctor may not treat HP unless you have stomach pains (a symptom of peptic ulcer). 

 

Tobacco and alcohol

Cigarette smoke contains many cancer causing chemicals. When you breathe in cigarette smoke, you will always swallow some of it without meaning to. In that way, smoking can increase the risk of stomach cancer. About 1 in 5 stomach cancers (20%) in the UK is thought to be caused by smoking.

People who smoke have around twice the risk of stomach cancer compared to non smokers. The risk falls if you stop smoking. If smokers have HP infection, they may have more than 10 times the risk of non smokers without HP infection.

A Swedish study showed that non smokers who use a type of chewing tobacco called snus increase their risk of stomach cancer by up to a half.

From recent research it seems unlikely that drinking alcohol increases the risk of stomach cancer.

 

Other medical conditions

Acid reflux is where acid from the stomach goes back up into the oesophagus (foodpipe). It can cause inflammation of the oesophagus (oesophagitis). Acid reflux may increase the risk of cancer in the upper part of the stomach closest to the oesophagus (gastric cardia). 

Some diseases and operations have been shown to increase the risk of stomach cancer because they lower the amount of acid produced in the stomach. The reduced acid level may allow more bacteria to grow and the bacteria may help to produce more nitrites and nitrosamines - chemicals that may increase stomach cancer risk. The diseases and operations include

 

Anti inflammatory drugs

An overview of published studies showed that people who regularly take non steroidal anti inflammatory drugs appear to have a slightly lower risk of stomach cancer. These drugs are called NSAIDs. Examples are aspirin, ibuprofen or Nurofen. Researchers in 2010 reviewed the trials looking at whether daily aspirin can protect against health conditions. They found that taking daily aspirin may reduce the risk of dying from stomach cancer. This needs more research though, and regular use of NSAIDs can increase the risk of developing stomach or duodenal ulcers.

 

Family history

Family history is being looked at as a risk factor for stomach cancer. Brothers, sisters, and children, of people with stomach cancer have an increased risk of getting it themselves. We're not sure whether this is genetic, or because they share other risk factors, such as Helicobacter pylori infection.

 

Having other cancers

Statistically, men have a slightly increased risk of stomach cancer if they've already had prostate cancer, breast cancer, bladder cancer or testicular cancer. Women have an increased stomach cancer risk if they've had ovarian cancer, breast cancer or cervical cancer. Both sexes have an increased risk if they've had food pipe (oesophageal) cancer, non melanoma skin cancer, bowel cancer, non Hodgkin's lymphoma or thyroid cancer.

 

Radiation exposure

Atomic bomb survivors in the 2nd World War were more likely to get stomach cancer because of the radiation they were exposed to. And we've known for many years that people who have had radiotherapy to the spine for a condition called ankylosing spondylitis have an increased risk.

Stomach cancer has also been linked to medical X-ray exposure in the past. These days, the amount of radiation used in a regular X-ray is much lower than it used to be. But some other medical tests, such as CT scans, use a significant amount of radiation. This is not harmful to you if you have scans only when you need them. But it explains why doctors are reluctant to use scans for routine screening.

 

Reduced immunity

People with suppressed immune systems due to infection with HIV, AIDS, or drugs taken following an organ transplant, have double the risk of stomach cancer compared to other people. This may be because they have an increased risk of infection such as Helicobacter pylori.

 

Work chemicals

The International Agency for Research on Cancer (IARC) states there is evidence that working in the rubber production industry increases the risk of stomach cancer. There may also be a link with exposure to asbestos.

 

Hormone replacement therapy (HRT)

Women who take hormone replacement therapy (HRT) have a reduced risk of stomach cancer. But HRT increases the risk of some other types of cancer, including breast cancer.

 

Blood group 

People with blood group A may be at a slight increase risk of developing stomach cancer. However that risk is still small. 

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Updated: 15 January 2014