Sleeping on the left side of the body is not harmful to the heart, explains doctors from HealthTap. In fact, there is some evidence sleeping on the left side helps lessen heartburn, and doctors may advise pregnant women to sleep on their left sides because it improves heart circulation, notes WebMD.
The position in which someone sleeps can have a profound impact on sleep quality and overall health, according to WebMD. Poor sleep posture can exacerbate symptoms of several health problems, such as sleep apnea, back pain, heartburn, fatigue and headaches. Those who suffer from sleep apnea, for example, should refrain from sleeping on their backs and instead sleep on their sides because doing so helps airways remain open. For the same reason, side sleeping is recommended for those who snore.
Those who do not have specific health-related reasons to sleep in a particular position should aim to sleep in the position that feels most natural to them and leaves them feeling most well-rested in the mornings, recommends WebMD. The mattress on which a person sleeps is also important, as a poor-quality mattress can make sleeping in the most natural position difficult. For example, it can be uncomfortable to sleep on the stomach or side with an old mattress that is worn out in the middle.