According to the Merck Manual the human body uses buffers to balance the pH.
Likewise the blood will produce more carbon dioxide and less bicarbonate if an alkaline substance is consumed.
Blood will produce more bicarbonate and less carbon dioxide to neutralize the acidity, So if a person consumes something acid. Sources.
Anyways, while concerning deionized and demineralized water, Should you know of any other interesting or more recent book, report, article or publication.