On Tue, 27 Aug 2002, Jeff Keller wrote:

> > I've heard from several random sources in the past week that a
> > "high protein diet is bad for the kidneys."
> >
> Cordain said that a 6 month study was done on a high protein diet and kidney
> function with no degradation in
> kidney function. I took little comfort in this statement or the fact that so
> little concern was placed on perhaps,
> the most sensitive organs to high protein intake.

This opinion, that high protein is "bad for the kidneys," appears
to be based on the fact that a high protein diet is in fact bad
for *diseased* kidneys, because of their weakened state.  But it
is a fallacy to think that if protein is bad for diseases kidneys
it must cause healthy kidneys to become diseased.  There is
simply no evidence for the latter claim.

My favorite analogy is this: Ice skating is bad for people with
weak ankles, because of the danger of a sprain.  It certainly
doesn't follow that ice skating causes weak ankles.  Vigorous
exercise may be bad for people with advanced heart disease, but
it doesn't cause heart disease.  And so on.

The general form of the fallacy is X is bad for people with
condition Y, therefore X is bad for everyone, or therefore X
causes condition Y.  It just doesn't follow.

A similar fallacy is involved in the inference from X is *good*
for people with condition Y, therefore X is good for everyone.

Todd Moody
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