Q.Knowing the properties of H2O and D2O, do you think that D2O can be used for drinking purposes?

D2O (heavy water) has the same chemical formula type as ordinary water but with deuterium in place of protium.

Although D2O closely resembles H2O in most physical and chemical properties, the two are not physiologically interchangeable:

• Biological systems have evolved around the specific mass/kinetics of protium; substituting deuterium changes reaction rates (the kinetic isotope effect), since bonds to the heavier D atom are typically stronger and break more slowly than corresponding O–H/N–H/C–H bonds.
• This slows down or disrupts many essential enzyme-catalysed and cell-division processes when D2O replaces a significant fraction of the water in an organism.
• In sufficient concentration, D2O is actually toxic to living cells/organisms — aquatic organisms cannot survive in pure D2O, and mammals show physiological disturbances if a large fraction of their body water is replaced by D2O. …

Note the chemical similarity but physiological difference between D2O and H2O, citing the kinetic isotope effect (D bonds break more slowly) as the reason …

• Assuming that because D2O is chemically almost identical to H2O it must also be safe to drink — biological/kinetic effects make this false. …