Most people choose a sleeping position without thinking much about it, then wake up with a stiff shoulder, heartburn, or the familiar urge to roll over.
In a new episode of SIC’s Chica Esperta, Portuguese physiotherapist Carlos Teles said left-side sleeping may support digestion and circulation, while challenging the idea that the body has one ideal posture. The episode, hosted by Ana Galvão, was released on July 23, 2026.
The most useful takeaway is not that everyone must stay frozen on the left all night. Current research gives the clearest support to that position for nighttime acid reflux, while the heart and breathing picture depends on pregnancy, sleep apnea, heart failure, pain, and personal comfort. A good position is one that helps a specific problem without creating another.
Left-side sleep and reflux
Gastroesophageal reflux disease, usually called GERD, happens when stomach contents travel backward into the esophagus, the tube carrying food to the stomach. That can cause burning behind the breastbone, sour liquid in the throat, coughing, or broken sleep.
Lying down removes some of gravity’s help, which is why dinner can seem to come back for a late-night visit.
The benefit appears to come partly from the way the stomach and esophagus are arranged. On the left side, gravity tends to keep more stomach contents below the opening to the esophagus, making backflow less likely. On the right, acid may remain in contact with the esophagus longer.
A 2023 systematic review led by Daniel Martin Simadibrata concluded that left-side sleeping could reduce nighttime reflux and improve GERD-related quality of life.
A separate sham-controlled study involving 100 people found that avoiding the right side reduced nighttime symptoms and improved sleep quality. That is meaningful evidence, although position is not a replacement for medical care or prescribed treatment.
The circulation claim needs context
Teles put the advice plainly, saying, “From a cardiorespiratory and digestive point of view, it is better to sleep on the left side.” He added that the position “favors circulation and digestive drainage.” Evidence is strongest for reflux, while broader circulation and digestive claims depend more heavily on the person’s health.
During later pregnancy, side sleeping can reduce pressure from the uterus on major blood vessels, and left-side positioning is often used to support blood flow. But healthy adults do not have a universal heart rule that makes the left side superior every night.
Some people with severe heart failure become more short of breath on their left side and naturally prefer the right.
Breathing changes the picture too
Breathing also changes with position. For many people with positional obstructive sleep apnea, sleeping on either side can help keep the airway more open than sleeping flat on the back.
The important distinction is “side” rather than always “left,” and diagnosed sleep apnea still needs proper evaluation and treatment.
Regular heart checkups help identify cardiovascular risks early. Experts say sleep position may influence some conditions, but overall heart health depends on many factors.
No single correct posture
The broader message from the episode may be even more useful during waking hours. “There is no single correct posture,” Teles said, arguing that people should change position, notice what their bodies are telling them, and use movement to release accumulated tension. Anyone who has sat through a long meeting knows the feeling.
Research supports that more flexible view. A systematic review published in 2020 found no consensus that particular spinal postures or physical activities directly cause low back pain, while workplace guidance from the World Health Organization has long advised changing posture often and alternating sitting with standing. The body is built to move, not to pose like a statue.
That does not mean posture never matters. A position held for too long can repeatedly load the same muscles and joints, and an injury may make one angle painful. But chasing a perfectly straight back every minute can distract from the simpler habit of moving regularly.
What to try tonight
People with nighttime heartburn can try starting on the left side, especially after discussing persistent symptoms with a clinician.
A pillow that keeps the neck level and another between the knees may make side sleeping easier. Also avoid lying down immediately after a large meal, since eating at least three hours before bed may reduce nighttime GERD symptoms.
For ordinary aches, the same rule applies. Switch sides if a shoulder, hip, or arm becomes numb, and adjust your support rather than forcing yourself through pain. There is little value in following a position rule that repeatedly wakes you or leaves you sore the next morning.
Seek medical advice if heartburn is frequent, pain persists, snoring comes with gasping or daytime sleepiness, or breathing becomes difficult when lying flat. Those are not problems to solve with a new pillow alone. Sometimes the body is not asking for a better pose, but for an examination.
The episode has been published by SIC in the Chica Esperta podcast.
