Peptic ulcers: what causes them?

helicobacter pylori

For many years it was thought that peptic ulcers (gastric ulcers or duodenal ulcers) were caused by stress, poor dietary habits (including eating too much rich, fatty or spicy foods), alcohol, caffeine and smoking. It was believed that these factors contributed to the build-up of stomach acids that eroded the protective lining of the stomach and duodenum. Because of this all the treatment at the time was directed at neutralising and inhibiting the stomach’s acid secretion.

H. pylori infection

However, research has now shown that although excessive stomach acid and lifestyle factors certainly do play a part in the development of ulcers, most ulcers occur as a result of infection by a bacterium known as Helicobacter pylori (H. pylori), a corkscrew-shaped organism which lives in the inner lining of the stomach. H. pylori was discovered by Australian researchers in a huge breakthrough which revolutionised the treatment of ulcers worldwide.

H. pylori infection is very common. Most adults in developing countries are infected. Infection rates are lower for Western countries — about 40 per cent of people over the age of 40 in Australia are thought to have it, and less than 10 per cent of children.

How is H. pylori infection acquired?

H. Pylori can be passed from person to person through direct contact with either saliva or faeces. Although doctors are not certain, they suspect the bacteria may be spread through sharing food, cutlery and utensils for eating and drinking with infected people. H. pylori has been detected in the saliva of infected people, leading scientists to think that it may also be spread by mouth-to-mouth contact, such as kissing. Inadequate hand washing after going to the toilet and untreated water are other ways that the bacteria can be spread. Most people with the infection do not develop ulcers, although after being infected many people may suffer an attack of gastritis, which is an inflammation of the stomach lining.

The infection is usually acquired in childhood. However, older adults who were children in the 1920s through to the 1940s are much more likely to be infected than the young children and adolescents of today.

Why some people with H. pylori infection develop ulcers where others who are also infected do not is not entirely clear. However, whether an infected person develops an ulcer or not may depend on their personal characteristics, or environmental or hereditary factors. Researchers are continuing to investigate this question.

How does H. pylori cause ulcers?

H. pylori bacteria can penetrate the stomach’s protective lining of mucus and can live there. It can do this because it produces an enzyme called urease. Urease produces neutralising agents which protect the H. pylori from the strong acid of the stomach.

The protective lining of the stomach and duodenum and the mucus the stomach secretes are there to protect them from the digestive juices of the stomach. When H. pylori is living in the stomach or duodenum, it can sometimes interfere with this protective mechanism and allow the acid to attack the protective lining. This causes breaks in the lining, leaving it open to erosion by the powerful digestive juices.

Other causes of ulcers

There are other factors also known to contribute to ulcer formation. These include the following.

  • NSAIDs. Long-term constant use of pain relievers called non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen and naproxen are a contributing factor. These are believed to make the stomach more vulnerable to the effects of stomach acid and pepsin, especially in older people or people taking them for a long time. If you are taking NSAIDs regularly on a long-term basis, you should talk to your doctor about how best to minimise the effects on your stomach.
  • Smoking. Studies show that this increases the risk of ulcer occurrence, as well as slowing down the healing of existing ulcers.
  • Stress. Although this is not considered to be a cause of ulcers, emotional stress may increase the pain of existing ulcers by stimulating the stomach to produce more acid in response to the stress. Physical stress, such as severe burns or injuries, increases the risk of developing ulcers.

There is no conclusive proof that caffeine and alcohol are factors in ulcer development.


1. Mayo Clinic. H. pylori infection. Updated May 2009.
2. BMJ Clinical Evidence. Helicobacter pylori infection. Sept 2006.
3. Woodhead M. H. pylori rates fall to 15%. 6minutes. 9 April 2008
4. BMJ Group. Patient leaflets. Stomach ulcers. Mar 2009