> I've heard from several random sources in the past week that a
> "high protein diet is bad for the kidneys."

"Fitness fats [aka essential fatty acids] are also
anti-catabolic. They're part of protein metabolism, and
prevent muscle break-down. Without fitness fats, protein can
become toxic (a warning for those who eat lots of protein to
build muscle, and avoid fats because they have been
misinformed by rampant fat phobia). Protein toxicity
on a fat-less diet was shown around the turn of the century
in studies done with starved dogs. Lack of fitness fats
causes weakness and clumsiness (motor incoordination)."
NOTE: the guy sells EFA supplements.
http://www.maxsportsmag.com/fatloss/issue22/22fl2.htm

Some web searching and asking both physicians and vets
resulted in the information that many such health care
persons feel that too much protein MAY put strain on the
kidneys from their having to excrete too much nitrogen and
this causes the body to be too acidic (another reason we
were all told to drink lots of water when dieting).  Or they
confuse what they call "protein toxicity" with "Rabbit
starvation."

See also:
http://www.mercola.com/article/Diet/carbohydrates/scientific_evidence_low_grains2.htm
""Rabbit Starvation" (a term coined by V. Stefansson to
describe the phenomenon of excessive dietary protein) often
occurred among explorers who would live for long periods of
time on extremely low fat small game animals (i.e. rabbits).
The condition was marked by nausea, vomiting, weight loss
and fatigue. "Rabbit Starvation" was reversible when the
percentage of daily calories from protein began to drop.
Although the "Rabbit Starvation" phenomenon could effect an
individual consuming a ketogenic diet, it is highly
improbable.
"In general, if one is consuming commercially available
meats (even chicken), the percentage of calories from fat
would be too high to induce this condition. In the modified
low carbohydrate diets, due to the varied food sources, the
risk of protein toxicity, for all practical purposes, is
non-existent."
Note: the gist of this article seems to be you get sick when
you eat too much protein without enough fat, especially if
you don't have the proper 6:3 balance.
--
   Elisi Tsayonah, AniWodi, ghigau,
   St Francis River Band of Cherokee