Sleeping on the left side is often recommended for people who experience nighttime acid reflux. The explanation involves the position of the stomach and the point where the esophagus connects to it.
When a person lies on the left side, the stomach generally sits below the connection between the stomach and the esophagus. This arrangement may make it less likely for stomach contents to flow backward into the esophagus. Research suggests that left-side sleeping can reduce nighttime acid exposure in some people, although it does not eliminate reflux completely.
By contrast, lying on the right side may make reflux more likely or prolong acid exposure for some individuals. The exact effect depends on a person's anatomy, the severity of their symptoms, and other factors.
It is important to understand that the left-side position is a practical strategy, not a cure. A person may still experience symptoms because of meal timing, the severity of reflux, medication needs, or other health conditions.
Comfort matters, too. Someone who has shoulder, hip, or back pain may find it difficult to remain on one side throughout the night. In that case, the goal is to find a position that supports comfortable sleep while incorporating other measures that may reduce reflux.
If you want to try left-side sleeping, change position gradually and pay attention to how your symptoms respond over several nights. Keeping a simple record of nighttime heartburn, meals, and sleep position may help you identify whether the change makes a noticeable difference.
Why Lying Flat Can Make Nighttime Symptoms Worse
Gravity plays an important role in keeping stomach contents from moving upward. When a person is upright, gravity helps food and liquid remain in the stomach and supports their movement through the digestive system.
When someone lies flat, that assistance is reduced. If stomach contents flow into the esophagus, they may remain there longer than they would while the person is standing or sitting upright. During sleep, swallowing and saliva production also decrease, reducing some of the body's normal mechanisms for clearing refluxed material.
This helps explain why people who feel relatively comfortable during the day may experience heartburn after going to bed. They may notice a burning sensation in the chest, a sour taste in the mouth, or discomfort that wakes them from sleep.
