FYI: Some information about urinary pH and cranberry juice consumption and 
its anti-bacterial effect. It's possible that it may not in fact increase 
blood pH. Apparenlty in the study ordinary water also increased urinary pH.

Marilyn

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http://www.blackwell-synergy.com/links/doi/10.1046/j.1464-410X.2003.04472.x/full/?cookieSet=1

Early studies claimed that cranberry juice caused a decrease in urinary pH 
[29,30]. Quinic and benzoic acids in cranberries are presumably precursors 
of the hippuric acid that is excreted by the kidneys, and thereby acidify 
the urine [30]. Recently, claims about the ability of cranberry juice to 
acidify urine have been disputed [13,17]. A study of the effect of cranberry 
juice on bacteriuria and pyuria found that a group drinking cranberry juice 
had a higher urinary pH than the placebo group [13], while there were no 
significant changes in urinary pH in the study with cranberry tablets [17]. 
In the present study, the pH increased after drinking cranberry juice 
(relative to the control) but drinking water also caused an increase in 
urinary pH. Similarly, calcium excretion decreased relative to the control 
after drinking juice or water. These results are puzzling but may have 
arisen as a result of subtle dietary changes when subjects were drinking the 
fluids.

http://grants.nih.gov/grants/guide/rfa-files/RFA-AT-03-004.html

Mechanism of Action for UTI

The mechanism of action of cranberry in treatment of UTI has not been
clearly elucidated, but several potential hypotheses have been
proposed.

High levels of benzoic acid have been detected in cranberry juice, and
until recently, it was suggested that the bacteriostatic effect of
cranberry juice was due to acidification of the urine.  Several
studies, however, have cast doubt on this mechanism.

Current belief is that the prevention of UTI is achieved by inhibiting
adhesion of the infecting bacteria, E. coli, to uroepithelial cells.
Bacterial adherence to these cells is a critical step in the
development of infection.  It is facilitated by fimbriae (proteinaceous
fibers on the bacterial cell well).  Fimbriae produce adhesins which
attach to receptors on uroepithelial cells.  It is hypothesized that
cranberry constituents act by preventing adhesion.  Thus, the causative
bacteria are flushed, preventing their colonization of the urinary
tract.  In addition, there has been a report of the potential of
cranberry juice to weaken attachment of E. coli to inert (nonliving)
surfaces for control of biofilm formation on urinary catheters.

Two components of cranberry juice have been shown to inhibit the
adherence of E. coli to uroepithelial cells in vitro.  The first is
fructose which may not survive absorption and metabolism intact to
reach the urinary bladder.  The second is a group of polymeric
proanthocyanidins; the chemical structures of three have been
elucidated.  Fructose inhibits the adherence of type-1 fimbriated E.
coli and proanthocyanidins inhibit the adherence of P-fimbriated E.
coli to uroepithelial cells.