From Randy Sharpe, Director of Testing at H2 Analytics and President/CEO at H2 Sciences Inc
“A crucial concept to understand about alkaline hydrogen water usually produced by ionizers (unlike new devices that primarily use PEM membranes that don't raise the pH) is the difference between its alkaline pH and its "alkalinity”.
Just because particular water has an alkaline pH (above 7), this does not mean that it has the capacity to have any significant influence on the pH of another system into which it might be introduced, especially if the system has multiple pH-regulatory mechanisms designed to prevent that from occurring (e.g. the human body).
That ability depends on the water's "alkalinity" (buffering capacity), not its pH.
While most drinking water does have some limited buffering capacity (depending on the number of carbonates & bicarbonates present), it will not have enough alkalinity to have a significant impact on the human body, where it will be overwhelmed by the extremely low pH of the stomach, which has the ability to produce acid on-demand to maintain its low pH (proton pumps).
On the other hand, it would be possible to produce alkaline-pH water using a buffering compound (e.g. baking soda), whose alkalinity was so high that, if you drank enough, it could overwhelm the blood's ability to maintain its critical 7.4 pH, possibly resulting in death (never try this!).
If you have any questions about your water's alkalinity, it can be measured using water test strips used for swimming pools & hot tubs.
With regards to hydrogen water and its negative ORP (oxidation or reduction potential), it is the dissolved hydrogen gas that produces the negative ORP reading. There is no "ideal" ORP because it is a measurement influenced slightly by the dissolved H2 but greatly by pH.
Therefore, depending on the water's pH, a -700 ORP can easily have less dissolved hydrogen than a -400 ORP. This is why, in order to measure dissolved H2, sophisticated methods (H2-specific probes or gas chromatography) that are not influenced by pH are required.
Comment: It’s increasingly obvious that most owners of electric (electrolysis) water ionizers have believed they are getting water with an alkalinity level equal to the pH reading their machine says - or the reagent they get with the machine says.
Randy’s article explodes this myth, and in particular, his comment about not enough alkalinity to have a significant impact on the human body. If you think you are drinking pH 8.5 water but its actual alkalinity is pH7.5, that means your expensive ionizer has had its way with you. :) It’s artificially boosted the pH reading but has NOT increased true alkalinity.
Of course, drinking true natural alkaline water does replenish our alkaline buffers. It’s just amazing that so many people bought hugely expensive water ionizers that only concentrate the alkaline minerals already in their tap water.
If you hear your salesperson equating high negative ORP with H2 levels.. beware.