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Carbonic Acid and Health
Name: Nick S.
Status: student
Age: 13
Location: N/A
Country: N/A
Date: 2001
Question:
While on vacation at Mammoth Cave the park ranger shared that
the caves were formed by carbonic acid and that the carbonic acid is soda
pop is 150 times greater than the acid that carved out the caves. If that
is true why doesn't the carbonic acid in pop cause damage to our teeth and
soft tissue?
Replies:
Most soda pop is quite acidic; I think Coke is about pH 3. Fortunately, our
bodies are able to handle acidic solutions to an extent. Our stomachs, for
example, are well-adapted to a mildly acidic environment since our own cells
pump out acid to aid in digestion. On the other hand, acid will react quite
nicely with bone. If you soak a chicken bone in acid long enough, and replace
the acid as it is neutralized by reacting with the bone, you will eventually
be able to bend the bone like one of those rubber doggy toys. (When people do
this for a demonstration, they usually use an acid stronger than Coke; I
do not know how long it will take with Coke...... try it). So why don't your
bones dissolve when you drink Coke? Lucky for you, your body fluids have a
wonderful capacity to buffer, meaning they can keep a stable pH under a
variety of conditions.
Paul Mahoney, Ph.D.
It does.
Chris Murphy
When comparing acids or more accurately hydrogen ion concentration [H+],
150X is not that much! E.g. going from the blood to the stomach, the [H+]
is around a million-fold increase! All cells/tissues have a variety of
buffers that neutralize excess H+. The stomach has mucus and other barriers
too that protect soft tissue. GI secretions (pancreas) also neutralize with
bicarbonates.
Without buffers a researcher cannot maintain cells in tissue culture - they
will quickly die!
Lou Harnisch
The acidity of soda is caused by the dissolved CO2 (carbonation) and the
presence of phosphoric acid, used as a buffer to keep the pH low. Given long
enough exposure, soda can attack tooth enamel; however, the dominant attack
is the acid formed by the growth of bacteria that feed on the sugar present
in soda. Also remember that acidity is usually measured on a logarithmic
scale (pH = - log[H+] ), so the "large" difference in the acidity means that
if the pH of soda is about 2, then the pH of the cave water is about 3.5. In
addition, the residence time of soda in the mouth is short and the tissue in
the stomach is already resistant to acid. In a healthy stomach the pH is (if
I recall correctly between pH = 1 or 2).
Vince Calder
Several reasons. The major one is that people only live for about 100
years, and Nature had millions of years to make Mammoth cave. Another is
that teeth are made of hydroxyapatite, a calcium phosphate mineral; caves
are usually carved from limestone rock, which is a calcium carbonate
mineral. Hydroxyapatite is more resistant to acid decomposition.
Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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Update: February 2012
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