Result of replacing all the water in a human body with "heavy water"

Has anyone done a study - or figured out theoretically - exactly what would happen to a human body if the water in it was replaced with heavy water? (Heavy water is water in which the hydrogen atoms/ions have a neutron in the nucleus along with the proton, making them “heavy hydrogen”.) I assume the resulting body would be heavier (by less than 10%), but since this change is at the atomic level would there be any of the usual problems associated with weight gain?

I read in the 1970s that heavy water is one of the rarest naturally occurring substances in the world, and the cost of the stuff was something like $20,000 an ounce; what with inflation and all, I suspect the cost of actually doing a study like that to be sort of prohibitive. But has anyone figured out, theoretically at least, what would happen in such a case?

Here’s a somewhat relevant SDStaff report:

Is Heavy Water dangerous?

Here’s the straight dope according to Q.E.D. In particular note paragraph four.

I think that mostly answers the question. My guess is that as well as being dead and setting off a few Geiger counters, you would probably sink in the pool as well.

You wouldn’t be setting off any Geiger counters (well, no more than usual) - deuterium isn’t radioactive. You might be thinking of tritium.

for what it’s worth, according to my calculations (I’ve always wanted to use that phrase), if all the water in your body were replace with deuterium oxide, your weight would increase by a little over 11 %.

Hmm. According to my calculations, it’s a little less than that.

Cecil says that D[sub]2[/sub]O has a density of 1.108g/cm[sup]3[/sup], so it is 10.8% heavier than normal water.

Taking a ballpark figure of 70% of the body by mass being water, I’d say the new weight would be [(1.108 x 0.7) + 0.3] = 1.0756, or about a 7.6% increase in weight.

Now, anyone care to volunteer to try this experiment with T[sub]2[/sub]O?

Where does heavy water occur naturally?

In water, and no I’m not being smart. Honest. :slight_smile:

Here’s a pdf paper by Atomic Energy Canada on Heavy Water. CANDU reactors use heavy water as opposed to regular water.

Incidentally, it doesn’t taste any different, but I do think it had a slightly different mouthfeel; it was very slightly viscous. This was also noticeable when we measured it in small quantities - 1 ml volumetric flasks and the like.

Working in the chemistry lab was fun . . .

Isn’t this contradictory? That is, if heavy water has different reaction speeds and different bond energies, then it is by definition not chemically identical to water. Unless “chemically identical” does not mean “having exactly the same chemical properties”.

Semantics, I suppose. I was using the phrase “chemically” to indicate that the electron structure–the primary determinant of the chemical nature of a substance–is identical. That is, the reaction products are the same for both. Admittedly, I could have been clearer on this point, but I don’t like to get too caught up in nitpicky details in my Staff Reports. :slight_smile: