While it sounds counterintuitive that too little stomach acid could be causing acid reflux, there are a few different ways this can be explained.
Why Low Stomach Acid Is a Common Cause of Acid Reflux
Having low stomach acid not only prevents you from being able to properly digest the food you eat, but it’s also been shown to increase your intra-abdominal pressure, or IAP (2).
When this pressure pushes against your stomach (and the undigested food in your stomach), it allows your stomach’s contents, including gastric acid, to reach your lower esophageal valve, or LES. You can think of your LES as the “gatekeeper” that keeps gastric acid and food in your stomach where it belongs, preventing it from traveling backwards.