Dr Mirkin:
> http://www.drmirkin.com/nutrition/1603.html
> 
> "Your stomach is so acidic that no food can change its acidity. ...

Marilyn Harris:
> If what he (Dr. Mirkin) says is true that no food can change the
> acidity of
> the stomach, then how can alkaline-rich foods be a factor to urine pH?

The acidity of foods is different from the effect that acidifying foods have
on the pH of bodily fluids like urine (before it reaches the kidneys). Milk
is an alkaline food but it has an acidifying effect on urine, whereas citrus
fruits are acidic but have an alkalizing effect on urine. I was confused by
the difference between "acidic" and "acidifying" myself at first too. When
Cordain writes that "all foods upon digestion ultimately must report to the
kidney as either acid or base" the key words are "*upon digestion*" and
"*report to the kidney*." In other words, foods that are alkaline in the
stomach can become acidic after digestion and vice-versa. To make things
more clear, Cordain and other experts should probably talk about
"acidifying" and "alkalizing" foods rather than "acidic" and "alkaline."

> Wouldn't the usual state of a normally healthy person's food that
> leaves the
> stomach be a certain pH which is fairly high and doesn't really change
> much?

Not by the time it gets to the kidneys.

> Buffering of pH is a normal human condition and utilizes calcium - but
> the
> question is does it rise and fall tremendously based on the
> alkalinity/acidity of your food intake (not your antacid intake [an
> abnormal
> factor).

As Cordain explained, when the urine pH gets below 5 and insufficient
bioavailable calcium is present, the body leaches calcium from the bones,
which is a possible contributor to osteoporosis. This is a normal response
by the kidneys, but if you keep hammering them with acid you run the risk of
potentially damaging your bones (and I would assume the kidneys as well).

Marilyn Harris:
> I have done some research which indicates that stomach pH can be
> changed if
> one were to eat antacids such as Tums or Rolaids. But that might
> indicate an
> unhealthy individual. I did not find reference to normal food changing
> the
> pH... I guess that is the question. One wants a good acid somach for
> proper
> digestion.

Again, the acid level in the stomach is a different topic than the
acidifying effect of certain foods on urine. You want your stomach fluid to
be highly acidic for digestion, but not your urine or other bodily fluids.
Think *after* the stomach (namely: kidneys). You have hydrochloric acid in
your stomach for digestion, but you wouldn't want hydrochloric acid going
into your kidneys.

> Research:
> 
> * * *
> 
> http://www.newton.dep.anl.gov/askasci/mole00/mole00091.htm
> So, in conclusion, pH is of crucial importance to our body. Should we
> worry about it, then?
> Not at all, because we can not control it. Biology has worked out an
> infinitive sensitive and effective way to do control the pH, and we
> can't
> overrule it even if we tried. 

This misses the point. When the bodily fluid reaches the kidneys it can be
too acidic for the kidneys to process, so the urine is buffered with calcium
to alkalize it. If not enough calcium is available, it is leached from the
bones. The result is urine that has a pH within the "narrow" range that the
critics talk about, but at the expense of bone density. The final objective
of balancing acidifying and alkalizing foods is not to control the urine's
pH, it's too stop the calcium leaching (and perhaps other potential harmful
effects yet to be discovered).

Jay from http://www.newton.dep.anl.gov/askasci/mole00/mole00091.htm:
> The only exception is the pH in the
> stomach,
> which can be turned to less acidic (taking anti-acids) during stomach
> complaints. 

Again, we're talking about acid levels *after* digestion (particularly in
the kidneys) here--not stomach acid.

> Even so, the 'signal' sent by such complaints should not be
> overlooked: when a 'healthy' stomach pH is suddenly causing trouble one
> should look for the underlying reason and not just treat the symptoms.

True, but a different topic than what we're discussing.

J. Stein Carter from http://biology.clc.uc.edu/courses/bio104/atom-h2o.htm:
> However, antacids such as TumsR or RolaidsR are so "strong" that they
> overwhelm the person's stomach's buffers' ability to function properly,
> drastically changing the pH of the stomach contents, and therefore,
> pepsin's
> ability to digest the protein in one's diet. Calcium, by the way, is
> absorbed better into one's body if the stomach contents are acidic,
> thus
> antacids also interfere with our bodies' ability to properly absorb
> calcium.
> To properly absorb dietary calcium, it should be consumed along with
> acidic
> or slightly acidic substances (such as milk or orange juice), and not
> mixed
> in with antacids.

Again, this excerpt is on stomach acid, not acid in the kidneys.

Hope this clears up a rather confusing subject.