Ask Dr. Universe – Water In Our Bodies

Why do we have water in our bodies? –Angelika, 12, Cathedral City, CA

Dear Angelika,

Believe it or not, we are mostly water. Of course, you may have noticed we aren’t sloshing around and spilling everywhere.

That’s because a lot of water in our bodies is found inside the cells that make us up. In fact, about 60 percent of our body is water, said my friend Yonas Demissie, a civil engineer and professor at Washington State University. He’s engineering ways to make sure people have good water resources for the future.

Every day, water is flowing in and out of our bodies. When we drink, water can do all kinds of good things for us.

Water in our blood helps carry nutrients, the important things we get from food, around the body. These nutrients take a ride in the blood and are delivered to your cells to help give you energy and keep your body fueled. That’s what I found out from my friend April Davis, an assistant professor of nutrition and exercise physiology at WSU.

One big reason we have water in our bodies is that it helps gives cells their structure, she said. It keeps cells a little plump. It also helps make different chemical reactions cells need to do their jobs.

Water is also in charge of moving things around the cell to keep it working. These cells make up our organs—like bones, lungs, and kidneys.

Water is a key ingredient for helping our organs stay healthy. In fact, our brain is about 70 percent water. Our lungs are about 90 percent water. The kidneys process about 50 gallons of blood each day. They process extra water your body doesn’t really need. Pretty soon, you’re running to the bathroom.

Another way water leaves the body is through sweating. If you’ve ever played soccer or just sat outside on a super hot day, you know you can sweat quite a bit. Water helps the body release heat. We do it through sweat. As the sweat evaporates from your skin, it also helps cool you down.

If we have too much water in our cells, our body has ways to get rid of it. But sometimes our cells actually don’t have enough water. We start to get thirsty and that signals our brains to find something to slurp up. There’s nothing like lapping up a cool, refreshing drink of water.

Water is so important to living things. But in some places, it is really hard for people to get clean water. Just here in the U.S. we use 10 times more than a person in countries where access to clean water is limited, said Demissie.

In Ethiopia, where he grew up, less than half the residents can get clean drinking water. Now, he’s using engineering to create water resources in our world, looking at how we can share them, and making sure that water is clean for people to drink. After all, water is important for every body, everywhere.

Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send in a question of your own at