Sleep is an essential component of good health. According to the U.S. Centers for Disease Control and Prevention (CDC), adults should aim for at least seven hours of sleep per night to support overall well-being, cognitive function, and physical health [CDC, 2022]. While the amount of sleep is important, research also suggests that sleep position may affect certain health outcomes.
One commonly discussed position is left-side sleeping. Though sleeping position is largely a matter of comfort and personal preference, some studies and expert guidelines indicate that left-side sleeping can have specific advantages in certain contexts. Below is an evidence-based overview of when and why sleeping on your left side might be recommended, and when it might not be the best choice.
Reducing Symptoms of Gastroesophageal Reflux Disease (GERD)
One of the most researched benefits of left-side sleeping involves managing acid reflux. Gastroesophageal reflux disease (GERD) is a condition in which stomach acid flows back into the esophagus, causing symptoms such as heartburn and discomfort.
Multiple studies have found that left-side sleeping can reduce nighttime acid reflux symptoms. A 2015 study published in The American Journal of Gastroenterology reported that participants who slept on their left side had significantly fewer and shorter reflux episodes compared to those who slept on their right side [Khoury et al., 2015].
This effect is believed to be due to the anatomy of the stomach and esophagus. When lying on the left side, the junction between the stomach and esophagus is higher than the stomach contents, reducing the likelihood of acid flowing upward.
Supporting Pregnancy Health
Left-side sleeping is widely recommended for pregnant women, especially in the second and third trimesters. According to the American College of Obstetricians and Gynecologists (ACOG), sleeping on the left side can improve blood flow to the heart, uterus, fetus, and kidneys, while reducing pressure on the liver [ACOG, 2023].
This position helps ensure optimal circulation for both the mother and the developing baby. Side sleeping in general is also associated with a reduced risk of stillbirth in late pregnancy compared to sleeping on the back, based on observational studies.
Supporting Digestive Function
Though robust clinical trials on this topic are limited, anatomical considerations suggest that left-side sleeping may help with digestive transit. The ileocecal valve, which connects the small and large intestines, is located on the right side of the body. Sleeping on the left side may encourage gravity-assisted movement of waste toward the large intestine.
While the evidence is mostly anatomical rather than trial-based, some practitioners suggest left-side sleeping may help ease digestion and support regular bowel movements [Sleep Foundation, 2024].
Impact on Heart Function
For the general, healthy population, there’s no strong evidence that sleeping on the left side provides a cardiovascular advantage. However, for some people with certain heart conditions, left-side sleeping might be uncomfortable.
A study in The Journal of the American College of Cardiology noted that people with heart failure often avoid the left side due to increased discomfort or breathing issues [Douglas et al., 2007]. Conversely, healthy people without cardiovascular disease are unlikely to experience problems with left-side sleeping.
Considerations for Liver and Spleen
Some sources suggest that sleeping on the left side may help with spleen drainage or liver function because of gravity-assisted circulation. However, direct clinical evidence supporting these claims is limited.
While it’s true that the liver is on the right side and the spleen on the left, there is currently no strong, peer-reviewed evidence proving that sleep position significantly affects detoxification of these organs in healthy individuals. The body’s detoxification systems operate continuously and are not known to be strongly position-dependent.
Individual Comfort and Pain Management
Most sleep experts agree that the best sleep position is the one that allows you to rest comfortably without pain or frequent waking. The Sleep Foundation emphasizes that personal comfort is crucial, and different positions may be better for people with specific conditions:
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Back sleeping may reduce pressure on the spine but can worsen snoring or sleep apnea.
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Right-side sleeping may be more comfortable for some but can increase reflux in people with GERD.
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Left-side sleeping can help with reflux but may increase pressure on the left shoulder.
Side sleeping in general can put more pressure on the hips and shoulders. People with arthritis or joint pain may need a supportive mattress or pillow to reduce discomfort.
When to Talk to a Healthcare Professional
If you have chronic pain, sleep apnea, GERD, or other health concerns affecting sleep quality, it is best to consult a healthcare professional. They can help determine the optimal sleeping position and may suggest other strategies, such as:
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Adjustable beds or wedge pillows for reflux
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Body pillows to maintain side-sleeping posture
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Proper mattress and pillow selection to reduce joint pain
Conclusion
Sleeping on your left side can offer clinically supported benefits, particularly for managing acid reflux and supporting circulation during pregnancy. However, sleep position remains a personal choice, and what matters most is comfort and overall sleep quality. For people with specific health conditions, professional guidance is recommended.
By making informed choices about sleep position and overall sleep hygiene, you can support your physical health and well-being.
Sources
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Centers for Disease Control and Prevention. “How Much Sleep Do I Need?” CDC, 2022. Link
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Khoury RM et al. “Left-Side Sleeping Position Reduces Nighttime Gastroesophageal Reflux.” Am J Gastroenterol. 2015;110(6):845-851. Link
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American College of Obstetricians and Gynecologists. “Sleep During Pregnancy.” ACOG, 2023. Link
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Sleep Foundation. “Best Sleep Position for Your Health.” Sleep Foundation, 2024. Link
