Taste of Heavy Water

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Hebrew University researchers discover the taste of heavy water

While it is not radioactive, heavy water is highly coveted for its unique atomic structure and properties, which allow it to be used in the production of nuclear power and weapons.

By IDAN ZONSHINE MAY 7, 2021 09:10

A view of the water nuclear reactor at Arak, Iran December 23, 2019. WANA (West Asia News Agency) via REUTERS
(photo credit: REUTERS)

An international team of researchers has discovered the answer to a long-standing puzzle within the scientific community, proving once and for all that D2O, or 'heavy water,' - a form of water which contains a different isotope deuterium (D), also known as 'heavy hydrogen' - has a sweet taste.

There is anecdotal evidence from 1935 that the taste of pure D2O is distinct from the neutral flavor in pure H2O, being described mostly as “sweet.” However, researchers in that study described their results as inconclusive.

The team, led by Masha Niv at Hebrew University of Jerusalem’s Institute of Biochemistry, Food Science and Nutrition and Pavel Jungwirth at the Czech Academy of Sciences, decided to examine whether the rumors of the water's taste were true using cell-based experiments, human subjects, mouse models and molecular dynamics simulations.

The study, which was published in Communications Biology last month, found that heavy water could be distinguished from regular water based on taste alone.

Moreover, the study also found that humans would likely be able to recognize the sweet smell, while rats would not.

Rats had been found in previous studies to show harmful effects when the D2O levels in their blood reached higher levels, though it has been deemed safe by scientists for oral ingestion in small doses by humans.

During the study, participants received 3 samples of water. Two samples were ordinary water and the third was heavy water.

Participants were asked to sniff the water, then to taste it while their noses were closed with clips, and finally to sip the water freely, without nose clips.

When the researchers added the carbolic acid salt lactisole, which inhibits sweet taste receptor T1R2/T1R3, to the heavy water sample, it decreased the sweet taste for humans and blocked the activation of sweet taste receptor at the cell-level.

This demonstrated to the researchers that the sweet taste receptor T1R2/T1R3, which is activated in humans by sugars and artificial sweeteners, is also activated by heavy water.

While it is not radioactive, heavy water is highly coveted for its unique atomic structure and properties, which allow it to be used in the production of nuclear power and weapons.

In certain types of nuclear reactors, heavy water's heavier hydrogen isotope acts as a neutron moderator and coolant, allowing it to slow down neutrons so they are more likely to react with certain uranium isotopes.

While its highly sought-after status leaves it with a high price tag, “a better understanding of our sweet taste receptors may lead to new ways of eliciting sweet sensation, without the sugar,” Niv said in a statement.

Since the sweet taste receptors which the heavy water ilicits responses from exist in tissues other than the human tongue, the findings could have future implications in the medical field as well.

“Our sweet taste receptor belongs to a very important family of receptors called GPCRs," Nev explained. "GPCRs are important drug targets and deeper insights into their activation mechanisms may deepen our understanding of this useful family of proteins”.

The most notable difference in physical properties between D2O and H2O is the roughly 10% higher density, which results in a heavier molecule with slightly higher freezing and boiling points.

Bonus-Here's a separate article on the safety of drinking Heavy Water.