As a regular side-sleeper, I can doze off on my right or left side—but I’ve long favored left-side sleeping. When a recent injury left me unable to sleep on my usual side, however, I had to stick to exclusively right-side sleeping, and pretty quickly after, I started to have some trouble with heartburn at night. After coming across a viral TikTok post from herbal practitioner Ali Ramadan claiming that sleeping on your left side is preferable for gastric health, I began to wonder if the change in sleep position may have caused my gastrointestinal discomfort.

According to science, I may have been right. Some research shows that the side on which you choose to sleep can affect your health. In terms of G.I. health, specifically, Ramadan’s TikTok video has some credibility. Gastroenterologist Ali Rezaie, MD, says there are benefits of sleeping on your left side when it comes to your G.I. system, particularly if you suffer from acid reflux.

But at the same time, there’s some research to suggest that sleeping on your left side—which, for an anatomy refresher, is where your heart is located—may not be ideal for cardiovascular health, especially in people with a heart condition. This mixed evidence on sleeping positions for side sleepers begs the question: Which side should you sleep on for optimal health?

Which side should you sleep on, left or right?

The answer to the “which side” question depends largely on whether you’re dealing with a particular health condition, given that specific side sleeping positions have been mostly shown to affect the gastrointestinal and cardiovascular systems. Off the bat, if you have no concerns in either area, there likely won’t be much difference to your health whether you choose a right or left side sleeping position—though side sleeping, in general, could be a good idea (more on that below).

Benefits of left side sleeping

If you suffer from any kind of heartburn (aka acid reflux) or gastroesophageal reflux disease (GERD), you’d likely do well to sleep on your left side, given that research has connected right-side sleeping to an increase in episodes of acid reflux¹ as compared to left-side sleeping. “This is likely due to the position of the stomach,” says Dr. Rezaie, “which lays over the final portion of the esophagus when we sleep on the right side.” (To be sure, that doesn’t mean there’s necessarily any gastrointestinal benefit to choosing left vs. right side if you don’t have heartburn, acid reflux, or any other stomach condition.)

“Research has connected right-side sleeping to an increase in episodes of acid reflux due to the position of the stomach, which lays over the final portion of the esophagus when we sleep on the right side.” —Ali Rezaie, MD, gastroenterologist

Relatedly, Dr. Rezaie notes that the position of your head while sleeping on your left side can influence digestive function, adding that “greater elevation of the head² has been associated with fewer reflux episodes at night.” While certain adjustable beds and bed frames allow you to elevate the head of the bed a few inches, you can also place bed risers under the two bedposts at the head of the bed to angle it up a bit, or Dr. Rezaie suggests using a wedge pillow to create a similar kind of lift for your upper body. All that said, if morning aches and pains are often your bigger concern, sleeping with your neck and spine in neutral alignment is best.

The only other health scenario where research suggests you should sleep on your left side over your right is during pregnancy, where sleeping on the left side may help facilitate better blood flow for both birthing person and baby. It was once thought that left side sleeping throughout pregnancy could also reduce the chances of a stillbirth, but a 2020 study found that sleep position likely doesn’t have much of an effect on birth outcomes³ for the first two trimesters—so, the third trimester is where left side sleeping is likely most important and beneficial.

Benefits of right side sleeping

There may be an upside to sleeping on your right side over your left, when it comes to cardiovascular health—but as with the gastrointestinal benefits of left side sleeping, the heart-related benefits of right side sleeping are far more relevant to those who have an existing heart condition than to those who do not.

For people with heart failure, in particular, there is evidence to suggest that sleeping on your left side can be detrimental compared to right side sleeping, says United Kingdom-based interventional cardiologist Thomas Snow, MBBCh, MRCP. “Heart failure is a condition where the pump of the heart is weakened and does not contract as effectively,” explains Dr. Snow, “and research has shown that patients with this condition often avoid their left side in favor of sleeping on their right⁴, as it may feel more comfortable and possibly reduce the impact of local pressure effects than if adopting a left-sided sleeping position.”

To that same point, a small 2018 study of 10 healthy subjects found that sleeping on the left side was associated with changes in electrocardiogram (ECG) readings⁵, which researchers attributed to shifts in the heart’s positioning overnight, due to gravity. By contrast, almost no difference in ECG activity was found when the participants slept on their right side; in this case, the positioning of the chest cavity prevented the heart from moving or turning.

That’s all to say, sleeping on the right side may be a more protective sleep position for the heart—but there’s still no evidence to suggest that sleeping on one side or the other will prevent or increase your risk of developing a heart condition if you don’t already have one.

Is side sleeping healthier than back or stomach sleeping?

The good news for the 60 percent of adults who prefer side sleeping⁶ is that sleeping on either side has its fair share of health benefits. For starters, it can help reduce snoring as compared to back sleeping, during which “the tongue and soft tissue of the throat can fall backward and cause obstruction to airflow,” says Dr. Snow. This body positioning can also contribute to sleep apnea⁷, he adds, which is a sleep disorder that causes lapses of breathing during sleep.

“Sleep apnea has been linked to increased blood pressure and has also been implicated in a heart rhythm disturbance known as atrial fibrillation,” adds Dr. Snow. Indeed, research has found that sleep apnea increases the risk of heart failure⁸ by 140 percent, the risk of stroke by 60 percent, and the risk of coronary heart disease by 30 percent. All of these health risks just make it that much more important for anyone who does have sleep apnea or who frequently snores (which is often associated with apnea) to choose a side over back sleeping position. Though keep in mind: Side sleeping cannot cure sleep apnea; if you think you have it, talk to your doctor about treatment options.

Side sleeping may also support your digestive health, regardless of which side you choose. “While there is not much good evidence, anecdotally, sleeping on your stomach is not considered ideal for digestion,” says Dr. Rezaie, adding that lying on your back can also make reflux worse.

And at the end of the day, side sleeping might also just be the most comfortable sleep position for various aches and pains. While stomach sleeping can smush together the vertebrae in the spine, triggering back or neck pain, back sleeping can cause an unnatural extension of the spine if the lower back isn’t properly supported, which can also worsen back pain.

All of that said, if you have shoulder or hip pain, you may still prefer to sleep on your back to lessen the pressure on those body parts—and if you don’t have any of the conditions noted above, there’s certainly no harm in doing so.

The bottom line

Unless you have a pre-existing health condition or are pregnant, there is very little evidence to suggest that you should sleep on one side versus the other for optimal health. That said, there’s plenty of research to support sleeping on *a* side versus on your back or stomach if you’re looking to optimize breathing at night, mitigate snoring, minimize certain aches and pains, and support your digestion.

Even so, clinicians agree that sleep quality is much more critical to support your overall health than being in any particular position in bed. “Poor sleep has been identified as a risk factor for cardiovascular disease and diabetes, and contributes to stress, inflammation, and depression,” says Dr. Snow. “There is no doubt that poor quality sleep does have long-term consequences for an individual’s quality of life and their risk of cardiovascular problems.”

Which is all to say, the best sleeping position for you is likely going to be the one in which you can fall asleep the most easily and doze the most soundly, says Dr. Rezaie.

—medically reviewed by Angela Holliday-Bell, MD