When the stomach gets low on acid.

A shortage of stomach acid can lead to cancer, possibly as a result of bacterial overgrowth and chronic inflammation, a study in mice indicates.

Too much stomach acid is a well-studied problem that can cause more than simple gastritis, an inflammation of the stomach lining. Excess acid can lead to heartburn and cause chronic inflammation of the esophagus, esophageal scarring, and even cancer.

Turning the tables, scientists recently found that too little stomach acid might cause its own problems, including pneumonia (SN: 10/30/04, p. 277).

In the new study of low stomach acid, Juanita L. Merchant, a gastroenterologist at the University of Michigan in Ann Arbor, and her colleagues studied 20 mice, half of which were genetically engineered to lack gastrin, the hormone that orchestrates stomach-add secretion. Six of the mice lacking gastrin developed stomach tumors at 12 months of age, but none of normal mice did, the researchers report in the March 31 Oncogene.

The mice lacking gastrin also had fewer stomach-lining cells die off, which is a normal, tumor-suppressing action. In this process, the body detects runaway cell growth and sends the aberrant cells into suicide mode. The gastrin-deficient mice lacked RUNX3, a protein that in normal mice can activate such programmed cell death. Merchant hypothesizes that inflammation brought on by excess bacterial growth might suppress RUNX3 production.

It's too early to draw a parallel between acid-deficient mice lacking all gastrin from birth and people who regularly take acid-blocking drugs for acid-reflux disease, Merchant says.--N.S.