Re: Sodium Homestasis

J. Moore (
Sun, 12 Nov 95 17:59:00 -0500 (J. Moore) writes:

JM> >We could (and can) get enough salt from vegetable sources, however,

HH> Has any human actually been put on absolute no salt diet?
HH> (I know about hypertensives, but they are allowed potassium
HH> salts,and they probably get sodium from other foods so it's
HH> probably a low sodim diet rather than no-sodium diet.)

Given the ubiquity of sodium, it would indeed be extremely
difficult to have an absolutely no-salt diet.

JM> >human tears and sweat are not even hypertonic, as I've pointed out
JM> >before); human have salt mechanisms -- including both salt appetite
JM> >and renal systems -- which indicate a non-marine ancestry.

HH> This 'salt appetite', business should indicate, if anything
HH> that we are somehow used to more salt than we get via
HH> vegetables and not non-marine ancestry. On the other hand
HH> salt is given to cattle and sheep too, so maybe it has nothing
HH> to do with anything.

You've put forward two possibilities there, and neither is correct.
Animals which exhibit "salt appetite" are those for whom such a
mechanism has had important survival value during their evolution.
Marine animals, for instance, have never had a need to search for
or crave salt -- quite the opposite. On the other hand, animals
such as humans, sheep, rats, rabbits -- and indeed most all
terrestrial non-carnivores (Carnivores get plenty of salt from meat)
-- have evolved in environments in which this salt appetite was a
crucial need, and consequently they typically exhibit such an appetite.

HH> It seems to be a learned response but how would we measure
HH> the amount of salt (sodium) we really need. It would seem
HH> to depend on the amount that's flushed out, and that in
HH> turn could depend on the amount we have in the body. There
HH> doesn't seem to be something like the glucose-insulin
HH> mechanism for regulation-- or is there some chemical that's
HH> somehow connected with salt?

A) Typically behavior due to innate mechanisms is modified by
B) There are a number of hormones involved in the regulation of
sodium regulation -- both salt appetite and sodium retention and
excretion. If you want to learn more on this and don't mind 600+
pages of science, Derek Denton's *The Hunger for Salt* (1982,
Springer-Verlag) is a good source.

Jim Moore (

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