Avoiding risk factors and increasing protective factors may help prevent stomach cancer.

Avoiding cancer risk factors may help prevent certain cancers. Risk factors include smoking, being overweight, and not getting enough exercise. Increasing protective factors such as quitting smoking, eating a healthy diet, and exercising may also help prevent some cancers. Talk to your doctor or other health care professional about how you might lower your risk of cancer.

The following are risk factors for stomach cancer:

Certain medical conditions

Having any of the following medical conditions may increase the risk of stomach cancer:

• Helicobacter pylori (H. pylori) infection of the stomach.

• Intestinal metaplasia (a condition in which the cells that line the stomach are replaced by cells that normally line the intestines).

• Chronic atrophic gastritis (thinning of the stomach lining caused by long-term inflammation of the stomach).

• Pernicious anemia (a type of anemia caused by vitamin B12 deficiency).

• Stomach (gastric) polyps.

Certain genetic conditions

Genetic conditions may increase the risk of stomach cancer in people with any of the following:

• A mother, father, sister, or brother who has had stomach cancer.

• Type A blood.

• Li-Fraumeni syndrome.

• Familial adenomatous polyposis (FAP).

• Hereditary nonpolyposis colon cancer (HNPCC; Lynch syndrome).

Diet

The risk of stomach cancer may be increased in people who:

• Eat a diet low in fruits and vegetables.

• Eat a diet high in salted or smoked foods.

• Eat foods that have not been prepared or stored the way they should be.

Environmental causes

Environmental factors that may increase the risk of stomach cancer include:

• Being exposed to radiation.

• Working in the rubber or coal industry.

The risk of stomach cancer is increased in people who come from countries where stomach cancer is common.

The following are protective factors that may decrease the risk of stomach cancer:

Stopping smoking

Studies show that smoking is linked with an increased risk of stomach cancer. Stopping smoking or never smoking decreases the risk of stomach cancer. Smokers who stop smoking lower their risk of having stomach cancer over time.

Treating Helicobacter pylori infection

Studies show that chronic infection with Helicobacter pylori (H. pylori) bacteria is linked to an increased risk of stomach cancer. When H. pylori bacteria infects the stomach, the stomach may become inflamed and cause changes in the cells that line the stomach. Over time, these cells become abnormal and may become cancer.

Some studies show that treating H. pylori infection with antibiotics lowers the risk of stomach cancer. More studies are needed to find out whether treating H. pylori infection with antibiotics lowers the number of deaths from stomach cancer or keeps changes in the stomach lining, that can lead to cancer, from getting worse.

It is not known if the following factors lower the risk of stomach cancer or have no effect on the risk of stomach cancer:

Diet

Not eating enough fresh fruits and vegetables is linked to an increased risk of stomach cancer. Some studies show that eating fruits and vegetables that are high in vitamin C and beta carotene may lower the risk of stomach cancer. Studies also show that whole-grain cereals, carotenoids, green tea, and substances found in garlic may lower the risk of stomach cancer.

It is not known if changing your diet to include more vegetables, fruits, and whole grains lowers your risk of stomach cancer.

Studies show that eating a diet with a lot of salt may increase the risk of stomach cancer. Many people in the United States now eat less salt to lower their risk of high blood pressure. This may be why rates of stomach cancer have decreased in the U.S.

Dietary supplements

It is not known if taking certain vitamins, minerals, and other dietary supplements helps lower the risk of stomach cancer. In China, a study of beta carotene, vitamin E, and selenium supplements in the diet showed a lower number of deaths from stomach cancer. The study may have included people who did not have these nutrients in their usual diets. It is not known if increased dietary supplements would have the same effect in people who already eat a healthy diet.

Other studies have not shown that taking dietary supplements such as beta carotene, vitamin C, vitamin E, or selenium lowers the risk of stomach cancer.

Cancer prevention clinical trials are used to study ways to prevent cancer.

Cancer prevention clinical trials are used to study ways to lower the risk of certain types of cancer. Some cancer prevention trials are done with healthy people who have not had cancer but who have an increased risk for cancer. Other prevention trials are done with people who have had cancer and are trying to prevent another cancer of the same type or to lower their chance of developing a new type of cancer. Other trials are done with healthy volunteers who are not known to have any risk factors for cancer.

The purpose of some cancer prevention clinical trials is to find out whether actions people take can prevent cancer. These may include eating fruits and vegetables, exercising, quitting smoking, or taking certain medicines, vitamins, minerals, or food supplements.

New ways to prevent stomach cancer are being studied in clinical trials.

Clinical trials are taking place in many parts of the country. Information about clinical trials can be found in the Clinical Trials section of the NCI Web site. Check NCI's list of cancer clinical trials for stomach cancer prevention that are now accepting patients.