This is Why You Should be Sleeping On Your Left Side.The left side of the body is the dominant lymphatic side. Your lymphatic system aids in the removal of toxins and waste from your body. So you could say it is pretty crucial.By sleeping on your left side, you may find that your body becomes more efficient at removing waste and toxins from your body as well as relieving acid reflux, as Medical Daily reports. One of my coworkers found this to be true when she was pregnant. If she slept on her right side, she would get awful heartburn and would not be able to sleep. However, when she slept on her left side, no heartburn. This has to do with the position of the stomach. The stomach is on the left side of the body, so by sleeping on that side, gravity is helping the stomach juices stay in place. Less heartburn.