"That'll keep you from suffering from acid reflux it keeps your stomach lower than your oesophagus which will help keep stomach acid from sliding up your throat. Studies have shown that patients who sleep on their left sides are less likely to suffer from acid reflux. The oesophagus and stomach connect at an angle. When you sleep on your right, the stomach is higher than the oesophagus allowing food and stomach acid to slide up your throat.

Remember, it is not advisable for you to go to bed immediately after eating. Wait for 2 to 3 hours."

(Source)