Harvard Health Letter

Do PPIs have long-term side effects?

Nexium and the other proton-pump inhibitors are great at reducing stomach acid, but that might have some unintended consequences.

 Madison Avenue has given stomach acid a bad name, but it's really kind of a bum rap. Dip into any physiology textbook, and you'll find that stomach acid serves several constructive purposes. Pepsin, an enzyme that is essential to the preliminary digestion of protein, needs an acidic environment in the stomach to be effective. The strongly acidic hydrochloric acid pumped out by cells in the lining of the stomach also plays a direct role in the early digestion of some foods. And stomach acidity is a built-in barrier to infection: many bacteria and other pathogenic fellow travelers don't make it out of the stomach alive because of the low pH levels they encounter there.

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