Mahesh wrote:
<<Is it not true that excess acidity of the blood is caused by high protein
and calcium has to be leached out of the bones to buffer the blood and so
that the kidneys can eliminate the excess protein?>>

Here's a different perspective:  A high-protein diet can lead to excessively
alkaline blood.  Seriously.

Here are some excerpts from the paper "Differences in Intermediary
Metabolism in Mental Illness," by Dr. George Watson [I don't have an exact
reference at the moment; it was published in _Psychological Reports_
sometime during the '60s, and is reprinted in Watson's book "Nutrition and
Your Mind" (1972)]:

<<Under conditions of normal pH, the volume of carbon dioxide produced
divided by the volume of oxygen consumed in a given period allows the
calculation of the respiratory quotient (R.Q.), which provides a clue to the
type of food being oxidized.  For example, the R.Q. of carbohydrate is 6/6
or 1 [...].  The average respiratory quotients for fat and protein are 0.71
and 0.80, respectively [...]>>

<<The volume of carbon dioxide expired during normal respiration is related
to the partial pressure of CO2 in the alveolar air.  Since the blood volume
of dissolved CO2 + H2CO2 is in the equilibrium with the pCO2 of the alveolar
air, the higher the blood level of dissolved CO2 plus carbonic acid, the
larger is the percentage of carbohydrate being oxidized.>>

If most of your energy comes from the oxidation of protein and fat, the
amount of dissolved CO2 + H2CO3 in your blood plasma is lower than if you
depended on carbohydrates.  In other words, a low-carb diet makes the blood
more alkaline, and a high-carb diet makes it more acidic.  This phenomenon
has been empirically verified by Dr. Watson and Rudolf Wiley, as well as a
friend of mine.  Purines, salt, and fat all decrease the acidity of the
blood.

I'm not sure how elevated uric acid levels affect the equation; Mahesh's
question is a good one.  I can only suggest that (1) the people who thrive
on meat-based diets aren't susceptible to high uric acid levels, because
they metabolize purines efficiently; and (2) the contribution of uric acid
to blood pH may be small (does anyone know?).

Pretending to be a biochemist,
-- Aaron Wieland