Negative ions are exceedingly beneficial for a person's metabolism as a means of enhancing human behavior.  They act in a complex mechanism to bring about hormone and biochemical reactions in the body and brain.  Negative ions act like pure water in washing away dirty poison.  Generally, the more negative ions you are exposed to, the better and more uplifted you feel.

You see, electricity puts into the tired body just what it most needs-life force, nerve force.  It’s a great doctor, I can tell you perhaps the greatest of all doctors.
Nikola Tesla New York Hearld March 14, 1895
(Inventor of Alternating Current)