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In this YouTube video from Cody's Lab, Cody claims that heavy water tastes sweet.

He does some fairly convincing comparisons but still expresses a little doubt that the effect is real.

Has this been studied by others? Is the effect verified and if so, what possible explanations exist?

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    $\begingroup$ Just as a side note: You might find the vibrational theory of olfaction interesting, see for example en.wikipedia.org/wiki/Vibration_theory_of_olfaction $\endgroup$
    – logical x 2
    Commented Dec 31, 2016 at 16:08
  • $\begingroup$ I find cold water sweeter than warm water and he did say that heavy water feels colder. $\endgroup$
    – jkd
    Commented Dec 31, 2016 at 19:50
  • $\begingroup$ @Tetrahydrocannabinol - I found Cody's youtube channel a while back, when he was embedding magnets in his fingers. He's certainly ... interesting. But I don't think most people would be advised to do many of the things he does. $\endgroup$
    – Periata Breatta
    Commented Jan 1, 2017 at 16:56

4 Answers 4

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According to H.C. Urey and G. Failla, Science 15 Mar 1935, Vol. 81, Issue 2098, pp. 273, there's no difference in the taste of ordinary and heavy water.

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    $\begingroup$ Very small sample size but an interesting reference indeed! (+1) $\endgroup$
    – Linear Christmas
    Commented Dec 31, 2016 at 15:56
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    $\begingroup$ And now one definitively shown to be wrong by the Abu, et. al. paper. $\endgroup$
    – matt_black
    Commented Apr 7, 2021 at 17:15
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OK, first of all I want to say I really dislike the videos that this guy puts out, since he is promoting unsafe handling of chemicals. He might know what he's doing, but it's a terrible example.

To the actual question: surprisingly there are nearly no sources on this. I can understand that this isn't something a lot of people would try nowadays, but I imagined that a lot of people tried 50 years ago or something like that.

There's one science article describing a blind taste test of three persons in comparison to distilled water, and they couldn't spot a difference.

Another paper describes a difference, and also cites older research that showed that rats avoid $\ce{D2O}$ if they have the option to choose. But that might also be smell. It is known that deuterated substances can have a different smell and taste.

Heavy water also has a higher density and viscosity, so that might also be a factor which makes it "taste" different. Fun fact: it also has a different color.

And well, he didn't do the testing in a scientific manner, which would at a minimum include a double-blind format.

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    $\begingroup$ Watch the video starting at 6:47. He let his girlfriend (or his sister, or someone, idk) taste taste taste it and she didn't know which tube contained normal water and which one contained heavy water. $\endgroup$
    – UTF-8
    Commented Dec 31, 2016 at 20:25
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    $\begingroup$ @UTF-8 The odds of it being sheer luck is 50%. No conclusions can be drawn from that. $\endgroup$
    – user
    Commented Jan 1, 2017 at 9:03
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    $\begingroup$ @Fermiparadox Well, my sister started studying biology.They had a group visit a lecture.That group tested some gene manipulation on mice. They had 8 mice in total so I guess probably at most 4 which got a treatment. My sister has no idea what's meant by some number and then "sigma" but the group said that everything equal to or above 0.5 σ is relevant for confirming their hypotheses. So if you compare it with what's called "science" in biology ... :D ;-) Of course it's just 2 people on YT allegedly tasting it. But a study involving 3 people stating the opposite isn't exactly meaningful either. $\endgroup$
    – UTF-8
    Commented Jan 1, 2017 at 9:14
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    $\begingroup$ It's educational, though. Extremely stupid is being reckless for no apparent gain. $\endgroup$
    – Cees Timmerman
    Commented Jan 1, 2017 at 22:49
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    $\begingroup$ He explains why biting sodium sounds like a terrible idea, and why his attempt is likely to succeed while warning people not to replicate it. He doesn't mess around doing the same stunt until it kills him and/or others. Was sodium metal generally known to taste tangy and turn tongue tips into soap before? I think not. $\endgroup$
    – Cees Timmerman
    Commented Jan 1, 2017 at 23:03
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From the abstract of the article by Abu et al. [1]:

Here we conclusively demonstrate that humans are, nevertheless, able to distinguish $\ce{D2O}$ from $\ce{H2O}$ by taste. Indeed, highly purified heavy water has a distinctly sweeter taste than same-purity normal water and adds to perceived sweetness of sweeteners. In contrast, mice do not prefer $\ce{D2O}$ over $\ce{H2O},$ indicating that they are not likely to perceive heavy water as sweet. For humans, the sweet taste of $\ce{D2O}$ is suppressed by lactisole, which is a known sweetness inhibitor acting via the TAS1R3 monomer of the TAS1R2/TAS1R3 sweet taste receptor. HEK 293T cells transfected with the TAS1R2/TAS1R3 heterodimer and the chimeric Gα16gust44 G-protein are activated by $\ce{D2O}$ but not by $\ce{H2O}$. The present study resolves a long-standing controversy about the taste of heavy water, confirms that its sweet taste is mediated by the human TAS1R2/TAS1R3 taste receptor, and opens way to future studies of potential sites and modes of action.

Reference

  1. Abu, N. B.; Mason, P. E.; Klein, H.; Dubovski, N.; Shoshan-Galeczki, Y. B.; Malach, E.; Pražienková, V.; Maletínská, L.; Tempra, C.; Chamorro, V. C.; Cvačka, J.; Behrens, M.; Niv, M. Y.; Jungwirth, P. Sweet Taste of Heavy Water. bioRxiv 2020, 2020.05.22.110205. DOI: 10.1101/2020.05.22.110205
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I tasted heavy water, assuming it had no taste, and was surprised by the sweet taste (Aldrich, Deuterium oxide, 99.9%). The bottle was old but still sealed. Three other people also described the content of the same bottle as slightly sweet, without knowing what my perception was.

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    $\begingroup$ Please expand on your answer - the OP asks, in addition to if this effect has been studied (not observed) and verified by others, what possible explanations exist. $\endgroup$
    – Todd Minehardt
    Commented Jan 11, 2018 at 15:40

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