Why we can't drink seawater?

If you’ve ever been to the beach, you’ll know there’s an awful lot of water in the sea. You might think that, if you get thirsty when you’re playing in the sand, you could just walk down to the water for a drink. However, although it looks just like normal water, seawater holds an invisible secret that makes it undrinkable: salt.

The salty sea

As you probably know from your trips to the seaside, seawater tastes very salty. In fact, around 3.5% of seawater is made up of salt, with some parts of the ocean saltier than others. For the fish, crabs, limpets and other creatures that live in the sea, these conditions are perfect. Their bodies have adapted to survive in salty conditions and they can live happily below the waves.

Humans however have adapted to live on fresh water. Although we do consume small amounts of salt, drinking a lot can be very harmful as our bodies aren’t able to cope with the saline overload. In fact, drinking salt water is worse for you than drinking no water at all as the level of salt contained in the liquid can actually dehydrate you.

How our bodies cope with salt

The salt we ingest every day from food and drink is dealt with by the kidneys. They get rid of excess salt by diluting it with water to produce urine. However, kidneys cannot make urine from water that has more than 2% salt, and as we’ve already seen, seawater contains around 3.5% salt. As Urine is less salty than seawater, your body would have to use up its H2O supplies in order to flush the salt out. Eventually you’d become very thirsty and dehydrated as your body would be using more water to get rid of the salt than you’d be getting from the seawater.

Drinking seawater

Although it’s not possible to take a glass and drink directly from the sea, there are people in some parts of the world who rely on the oceans for their supply of freshwater. However, before they can drink it, the water has to be desalinated. This means all of the salt is taken out of the liquid to leave pure H2O for humans to enjoy. Desalination is used a lot on islands where there is no supply of fresh water and on smaller boats that are at sea for long periods of time.

To find out more about hydration and the importance of drinking water, explore our site or contact a friendly member of our team today.