So many medicines that lower stomach acid are advertised on television and in magazines. Don't we need stomach acid?

As with many things in medicine, there are good things and bad things about stomach acid. Much of medicine is an evaluation of relative risks and benefits of competing or contradictory imperatives. Stomach acid is good as long as it remains in the stomach. It helps kill swallowed mouth bacteria so that they don't travel into the small intestine and interfere with digestion and absorption. Stomach acid also converts ingested food iron and medicinal iron into a form which is better absorbed from the first part of the small intestine. Stomach acid also helps with the release of Intrinsic Factor, a material which helps vitamin B12 absorption at the end of the small bowel. When stomach acid gets into the esophagus, it causes inflammation of the lining of the esophagus (esophagitis) and increases the risk of stricturing (scarring shut) the bottom end of the esophagus or the risk of cancer in the lower esophagus. When stomach acid comes up all the way into the throat or mouth, it can cause vocal cord damage (reflux laryngitis), can etch the teeth, or it can get into the lungs where it can cause a severe chemical pneumonia. In fact, the leading cause of adult asthma is nocturnal reflux and aspiration of stomach acid into the lungs. Acid lowering medicines reduce the risk of harmful problems caused by stomach acid getting out of the stomach, but at the same time may reduce some of the benefits of stomach acid within the stomach. Again it is a matter of weighing one set of benefits against another and weighing one set of risks against another.