I have no personal opinion on the validity of the acid/alkaline theory but here is a contrary position by an MD:
http://www.quackwatch.org/01Quackery...SH/coral2.html
Acid/Alkaline Theory of Disease Is Nonsense
I also read somewhere in the distant past that the theory of the acidic environment as enhancing cancer progression was based on the wrong assessment of the cause & effect in the fact that cancer cells release lactic acid ( not the acid causing cancer).