The thing is that in the left part holds much of the lymph nodes. And while you sleep on this side, your body effectively filters toxins, lymph and wastes through the thoracic duct and lymph nodes.
On the other hand, sleep on the right side of the body slow down your lymphatic system. This leads to the fact that the system of purifying your body working inefficiently. As a result, the risk of fatal diseases due to excessive accumulation of toxins.
In addition, it was found that during sleep on your left side more effectively functioning digestive system. So if you have a habit to eat at night, take these recommendations with more than usual seriousness.
Also interesting: don't be fooled into thinking that sleep is less important than the urgent business Laws of the night: how to sleep in order to live productively