Most of us are also familiar with the old adage: Drink eight glasses of water at 8 ounces daily. The eight-by-eight rule guides us to drink 64 ounces (about 1.9 liters) of water each day. Many of us have blindly followed this advice for our entire lives, not knowing where it came from or why we need eight glasses of water.

Drinking water is a bit like breathing: we know it's vital, but we don't always think about it. Yet, hydration plays a key role in the functioning of our bodies, from our brain to our skin, including our muscles and organs.