Can Humans Taste Water? Science Says Yes

For years, the idea that humans can't taste water has been repeated in science classrooms and trivia nights. The claim goes that unlike some animals, we only detect the minerals and impurities in water—never the water itself. But groundbreaking research from Caltech and other institutions has debunked this myth entirely.

Humans absolutely can taste water. And the mechanism is fascinating.

The Sixth Taste Sense

We all know the five basic tastes: sweet, sour, salty, bitter, and umami. But neuroscientists have discovered what might be considered a sixth sense on the tongue—the ability to detect pure water. When researchers at Caltech applied deionized water to mice tongues, specific taste nerves fired in response. Not to minerals. Not to impurities. To the water itself.

The key player? Sour taste cells. These acid-sensing taste receptor cells (TRCs) detect water by sensing the pH change that occurs when water dilutes saliva. It's an elegant biological sensor that helps mammals—including humans—distinguish water from other liquids.

Heavy Water Tastes Sweet

In 2021, researchers took water taste testing to another level. They gave 28 human participants highly purified heavy water (D₂O, where hydrogen atoms are replaced with deuterium) alongside regular H₂O. The result? People could tell the difference. Most participants described heavy water as noticeably sweeter than normal water.

The sweetness comes from the TAS1R2/TAS1R3 receptor—the same one that detects sugar and artificial sweeteners. This wasn't about detecting impurities; both samples were highly purified. Humans were literally tasting the molecular difference between types of water.

Thirsty Mice and Laser Light

One of the most creative experiments involved optogenetics—using light to control cells. Researchers bred mice with light-sensitive proteins in their water-detecting taste cells. When these mice were given access to a spout that delivered blue laser light instead of water, they drank it obsessively. Some licked the light spout 2,000 times in 10 minutes, as if they were genuinely quenching their thirst.

The mice weren't confused or broken—they were responding to the exact same neural signal that water triggers. Their brains couldn't tell the difference between actual water and the artificial activation of water taste cells.

Why the Myth Persisted

The confusion likely stems from the fact that water doesn't trigger the traditional sweet, salty, sour, bitter, or umami receptors in obvious ways. Water's taste is subtle—more of a sensation than a flavor. Plus, we're constantly tasting it, so we've adapted to ignore the signal unless we're thirsty.

But subtle doesn't mean absent. Brain imaging studies show that specific regions of human cortex light up in response to water, separate from responses to other tastants.

So the next time someone tells you humans can't taste water, you can tell them: we can. We just needed better science to prove it.