Monday, August 07, 2006

New Ways To Put Fires Out

Stomach acid has been getting a bad rap for years. Witness all the ads for antacids that block its production to ease your pain. Besides easing the symptoms of indigestion, use of antacids was supported by studies that associated a chronic condition of "too much stomach acid" with stomach cancer. Nonetheless, longtime readers have seen us write repeatedly about the importance of healthy complete digestion and how an adequate level of stomach acid is critical to that process. So it didn't surprise me too much when researchers at the University of Michigan Medical School discovered that too little stomach acid also can lead to stomach cancer. The study author was Juanita L. Merchant, MD, PhD, professor of internal medicine and of molecular and integrative physiology. When I discussed the findings with her, she explained that stomach inflammation -- whatever its cause -- can lead to the development of stomach cancer, and this study revealed that chronic inflammation can result from too little acid. Her study was performed on a group of mice that had been genetically engineered so that they no longer had the gene that is responsible for gastrin, the hormone that stimulates the production of hydrochloric acid (which is stomach acid). Without gastrin, of course, the mice ended up with almost no gastric acid. As a result, they developed chronic gastritis (inflammation of the stomach). Their condition progressed to atrophy of the stomach lining, which eventually led to gastric cancer.

The role of acid in the stomach, says Dr. Merchant, is actually more of a security guard, helping protect the stomach from invading microorganisms, than it is a tool for breaking down food for digestion (though some fats, salts and nutrients do enter the body directly from the stomach). Food coming into the stomach is far from sterile. Acid protects the stomach lining from microorganisms that are ingested with the food, while starting the process of sterilizing food so that by the time it gets into the small intestine, it is relatively clean. With too little acid, bacteria enters the stomach, causing the immune system to respond by sending in inflammation to kill the "invaders."

Researchers are now discovering that the inflammatory response also attacks certain stomach cells, one of which makes the hydrochloric acid or possibly gastrin. When inflammation becomes a chronic condition, the acid-producing cells may be lost to the stomach, which then leaves it vulnerable to abnormal cell formation and tumor growth.

There is no way to know when stomach cancer starts to develop in a person, says Dr. Merchant, but it takes from 20 years to 40 years to do so. (Most people are between the ages of 50 and 70 when diagnosed.) It appears that many people who develop stomach cancer ingested something at some point in the past that carried destructive bacteria, most often the Helicobacter pylori bug that is responsible for up to 90% of stomach ulcers. Once H. pylori and possibly other bugs settle in, the immune system sends antibodies into the bloodstream, but it can't destroy H. pylori because the bug stays in the stomach lining. The immune system doesn't give up, however, and the consequence is chronic inflammation. Why H. pylori creates this situation in some people and not in others is something that just isn't known at this point.

This research has several implications for humans, says Dr. Merchant. She notes that antacids have their place in the easing of acid reflux as well as to aid in healing ulcers and addressing its symptoms, and they are safe for very short-term, intermittent use. However, ongoing use of antacids leaves the stomach vulnerable to irritation from these outside invaders. Doctors are particularly concerned about the obese pediatric population, where many cases of acid reflux have already developed. The children treat the condition with higher-powered antacids called proton-pump inhibitors (PPI) -- esomeprazole (Nexium), lansoprazole (Prevacid) and omeprazole (Prilosec) -- that can make them vulnerable to inflammation. Doctors are concerned about the long-term risk of taking the PPIs. Looking to the future, Dr. Merchant points out the need for a diagnostic tool that will reveal abnormal changes early while there is still time to intervene and correct the problem. By identifying pre-cancerous conditions, doctors could investigate tissue samples and if necessary treat the cancer before it takes hold. She adds that achieving this goal is still far away, but this study has made important steps toward that end. In the meanwhile, go easy on the antacids.

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