Here's why your saliva won't quench your thirst when it's hot outside

This weekend is set to be one of the hottest of the summer.

Our bodies can do a lot for us to help us deal with the heat, such as sweating to reduce our core temperature. But one thing that it can't do is provide us with a self-made beverage to quench our thirst.

That's right - even though saliva is made up of around 98% water, it simply can't give us the same benefits as drinking a glass of water. This seems a little counterintuitive considering our salivary glands produce up to two liters of liquids a day.

Dr. Len Horovitz at New York City's Lenox Hill Hospital told LiveScience that the reason saliva can't hydrate us is because it is concentrated with things such as proteins, enzymes, and electrolytes - much more so than the water we drink.

This causes a problem with osmosis, a process where when two liquids of different concentrations are separated by a membrane (such as the membranes of our cells), the liquid with the lower concentration flows in the direction of the liquid with the higher concentration in an attempt to even out the concentration levels of both.

Since freshwater is much less concentrated in salts and other solutes than the fluids in our body, when we drink it, our body's cells are able to absorb it via osmosis, resulting in that satisfying feeling of a quenched thirst.

But the concentration of saliva is too high, so it can't be absorbed by osmosis. In fact, if we drink it, it will likely make us feel more thirsty because it is actually more concentrated than our body's fluids.

To make matters worse, when it is hot out, our saliva becomes even more concentrated when our bodies start to lose water through sweat.

So while desperation might lead people to try to swallow their own saliva to satisfy their thirst, it simply is never going to work. The best bet this weekend, and in any time during hot weather, is to always keep a water bottle handy and stay hydrated.