That sentence is usually from a clickbait-style health claim and it’s typically referring to digestion or acid reflux.
The most common “completion” is something like:
“…you should have more acid reflux / heartburn if you sleep on your right side.”
This idea comes from how body position can affect Gastroesophageal reflux disease. When you lie on your right side, the stomach can sit in a way that makes it easier for stomach acid to flow back up the esophagus. Some studies suggest people with GERD may experience fewer symptoms when sleeping on the left side instead.
But it’s not a strict rule for everyone. Sleep posture alone doesn’t determine whether someone gets heartburn—diet, meal timing, weight, and individual anatomy matter much more.
If you want, you can paste the full line or the source you saw (“See more” usually means social media), and I can break down exactly what it was trying to claim.
