WEDNESDAY, Oct. 15 (HealthDay News) -- A common stomach bacteria may protect against a certain form of esophageal cancer, a new review suggests.

People with H. pylori strains that also had the CagA gene were almost half as likely to get adenocarcinoma of the esophagus, a cancer that develops in the tube that passes food from the throat to the stomach, according to the report published in the October issue of Cancer Prevention Research.

"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 esophagus," study co-author Dr. Farin Kamangar, a research fellow at the National Cancer Institute, said in an American Association for Cancer Research news release. "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."

About half the world's population has H. pylori, which is a known cause of stomach cancer and ulcers. As proper sanitation and antibiotics have become more prevalent in the world, H. pylori has become less common, and the number of stomach cancers and ulcers has subsequently dropped.

However, CagA-positive H. pylori has also dropped, while esophageal adenocarcinomas have increased -- two facts the study authors suggested are linked. Esophageal adenocarcinoma, at one time a rare cancer, now makes up about half of all esophageal cancer cases in Western countries such as the United States and the United Kingdom.

Despite its deadly potential, the stomach bacteria's longtime co-existence with humans suggests it also may have some beneficial effects, including possible roles in reducing diarrheal diseases and asthma, Kamangar said.

More information

The American Cancer Society has more about esophageal cancer.