It’s important to start here, because the journey of water in our bodies actually starts with the urge to drink water. The neuroscience behind thirst is quite complex, and also interesting, as scientists are still trying to fully understand how our brain drives us to look for water. 

We do know that staying hydrated is crucial for our bodies, and keeps our digestion functioning smoothly, keeps headaches away, and helps our bodies deliver nutrients to our cells. Hydration also keeps our bodies at the proper temperatures and helps us eliminate waste. And when we’re starting to run low on water, there are many triggers in our bodies that signal to our brains that it’s time to take a drink of water.

After our brains detect that our water levels are low and we need to reach for a full-to-the-brim Nalgene bottle, we take a sip. From our mouths, the water then travels down into our stomachs, before it makes its way into our gastro-intestinal tract. It takes our bodies about 10-20 minutes to digest just plain water, and it’s mostly absorbed early on in the small intestine.

After this is when things get really interesting. Water passes through the walls of our intestines into the plasma in our blood, and those water molecules are then transported all over the body by our vascular system. That water is distributed all over our bodies, including to different organs. 

In general, the adult human body is about 60% water, and individual organs are made up of ranging amounts of water. For example, our brains are about 75% water and our blood is 83% water, while adipose tissue (also known as body fat) is only about 10% water. 

After water is distributed, its journey in our bodies isn’t over yet. As we all know, it’s necessary to continually drink more water throughout the day, because human bodies lose water through various ways. Usually, the largest amount of water loss happens through urinary water loss, and it’s one of the major functions of the kidneys. Kidneys filter blood and remove waste and extra water, and we then eliminate that water through urination. 

Aside from that, water leaves our bodies through other ways. Sweating is another main cause of water loss, and the amount of water we lose from sweating can vary greatly depending on how much we’re sweating. You might not realize it, but we also lose water through breathing. When we breathe, air is moved into and out of the lungs, and that air has to be humidified before we breathe it out.

Understanding how water functions in our bodies isn’t just cool and interesting (were we the only ones thinking that?). It’s important to understand the journey of water, so we can connect the dots in our own minds and understand why we should all drink more water, and always keep a full Nalgene bottle by our sides. 

So let’s dig a little deeper. From regulating your body temperature to helping with digestion, staying hydrated is more important than you might think. Here’s some more of the science of how water interacts with our bodies.