Stomach bacteria may prevent some oesophageal cancers
US and Iranian scientists have found more evidence that some stomach bacteria may help to protect against the development of a form of oesophageal (gullet) cancer called adenocarcinoma.
The team carried out a review of 19 published studies investigating the link between the bacterium Helicobacter pylori, which lives in the human stomach, and two forms of gullet cancer - adenocarcinoma and squamous cell carcinoma.
They found that people who had H. pylori strains carrying a gene called CagA were almost half as likely to get oesophageal adenocarcinoma.
Study co-author Dr Farin Kamangar, a research fellow at the US National Cancer Institute, commented: "CagA-positive strains of H. pylori may decrease the risk of adenocarcinoma by reducing acid production in the stomach and, therefore, reducing acid reflux to the oesophagus.
"It may also work by decreasing the production of the hormone ghrelin, which is secreted from the stomach to stimulate appetite. A reduction in the level of ghrelin may lead to lower rates of obesity, an important risk factor for adenocarcinoma."
The finding that H. pylori may reduce the chances of gullet cancer is interesting as infection with the bacterium increases the likelihood of stomach cancer developing.
As the world's sanitation and antibiotics have improved, the incidence of stomach cancer has fallen.
Meanwhile, the incidence of oesophageal adenocarcinoma has increased and the latest findings, which appear in the journal Cancer Prevention Research, may help to partially explain the trend, although rising obesity rates are also thought to be an important factor.