Scientists from the Czech Republic, Israel, and Germany, as a result of laboratory experiments and molecular modeling, have found that humans have receptors that are activated under the influence of heavy water. This puts the final point in the scientific debate about whether it is possible to distinguish heavy water from ordinary water by taste. The article was published in the journal Communications Biology.
Heavy water has the same chemical formula as ordinary water, but instead of two atoms of the light isotope of hydrogen, protium, it contains two atoms of its heavy isotope, deuterium. The basic chemical properties of D2O and H2O, such as pH, melting, and boiling points, are very similar.
The two substances differ only in density – in heavy water, it is about 10 percent more. This difference is solely due to nuclear quantum effects, namely zero point changes that result in a slightly stronger hydrogen bond in D2O compared to H2O.
However, back in the 1930s, immediately after the discovery of heavy water by American chemist Harold Urey, unofficial evidence appeared that heavy water can be easily distinguished from ordinary water – it tastes sweet.
Despite the fact that Yuri himself, who received the Nobel Prize in Chemistry for his discovery, authoritatively stated that heavy water does not have any special taste, the debate about whether it is possible to distinguish D2O from H2O by taste is still ongoing.
Researchers from the Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, led by Pavel Jungwirth, together with colleagues from the Hebrew University of Jerusalem and the Technical University of Munich, conducted experiments on cell cultures and mice, as well as tests on humans, and the results were processed using models molecular dynamics.
The authors found that humans do have sweet taste receptors, TAS1R2 / TAS1R3, which are activated by heavy water. Mice do not have such receptors, so people feel the sweet taste of D2O, but rodents do not.
To test their hypothesis, the scientists used the sweetness inhibitor lactitol, which acts through the TAS1R2 / TAS1R3 receptors in human tests.
With the introduction of lactitol, people no longer taste the sweet taste of heavy water.
“Although the two isotopes are nominally chemically identical, we have conclusively shown that humans can taste, based on chemical perception, H2O from D2O – the latter has a distinctly sweet taste,” according to a press release from the Czech Institute of Organic Chemistry and Biochemistry. Paul Jungwirth’s words: “Our study thus resolves an old debate about the special taste of heavy water, demonstrating that a small nuclear quantum effect can have a marked effect on a basic biological function such as taste recognition.”
The authors plan to further study the effects of heavy water on human receptors – not only those on the tongue but also on the skin. Heavy water is used in medical procedures, and this information, according to scientists, can be useful for doctors and patients.