PNAS Journal Club: In the 1930s, scientists discovered a heavier form of water. So-called “heavy water” (D2O) weighs more because the nucleus of each of its two hydrogen atoms contains not just a proton but a neutron as well. Known as deuterium, heavy hydrogen causes subtle differences in heavy water—from small increases in boiling and freezing points to a roughly 10% increase in density.
Now, an international team of researchers has confirmed another difference long rumored to be true: Heavy water tastes sweet. “It’s a very gentle sweetness,” says study author Masha Niv, a taste scientist at the Hebrew University of Jerusalem. “It’s not like Sweet’n Low.”
Heavy water won’t work as a sweetener. Indeed, in large quantities, it’s lethal. But the work, recently reported in Communications Biology, could inspire a deeper understanding of how the sweet taste receptor works.
Heavy water’s flavor has rarely been formally tested as part of an experiment. Harold Urey, who discovered deuterium, tasted heavy water in 1935 and reported with a colleague in Science that it was no different than regular water. And a more recent study relied on human sensory studies alone to investigate. But anecdotally, some chemists have reported that heavy water tastes sweet—including Niv’s coauthors, chemists Pavel Jungwirth and Phil Mason of the Czech Academy of Sciences in Prague. So they and collaborators decided to put that sweetness to the test.