I really believe in it as a mouth wash, though I do not usually need it. I also sometimes take sodium bicarb down if I feel gout coming on, and it stops it dead. As I understand it, the key parts of our body regulate their own pH, so the blood, for example, takes care of itself, stays neutral, and is unaffected by changes in the pH of body fluids; the stomach maintains quite an acidic pH in order to break food down. I do think sodium bicarb is useful for lowering uric acid levels, which in my case I believe can cause gout and kidney issues, etc. But one does need to be careful. In the old days, people used to get stomach ulcers from overuse of antacids, because the stomach needs acidity.

Did your hygienist just measure mouth pH or something else? I am pretty sure mouth pH is localised, which is why I can have a neutral saliva and an acidic urine. I have these little pH strips that I can suck, and they go certain colours, like the litmus paper in school experiments. Not that I bother any more, because I am certain my diet takes care of all that.