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Re: Sodium Homestasis
J. Moore (j#d#.moore@canrem.com)
Wed, 8 Nov 95 13:43:00 -0500
Hu> If humans did not actively harvest salt and did not put it into food and
Hu> only drank fresh water (i.e. from streams) or fresh water lakes, could
Hu> we get enough salt from vegetables or do we need to eat animal flesh?
We could (and can) get enough salt from vegetable sources, however,
our ancestors probably also ate termites, ants, and small animals,
as do chimpanzees. These sources would provide more salt than
vegetable foods alone. Like many animals, including chimpanzees,
gorillas, orang utans, and modern humans, our ancestors probably
sometimes ate mineral-laden soils as well.
Hu> Do shellfish have much salt?
Shellfish and sea plants contain an enormous amount of salt, which
is why the marine mammals which eat them have kidneys which are
extremely large and heavily lobulated to deal with this massive salt
load. To maintain the required sodium to water balance in their
bodies, they need to be able to excrete not only a hypertonic
urine, but one which is saltier than seawater, since shellfish and
marine plants have a salt content approximately the same as seawater.
Humans, on the other hand, cannot produce urine that salty (and
human tears and sweat are not even hypertonic, as I've pointed out
before); human have salt mechanisms -- including both salt appetite
and renal systems -- which indicate a non-marine ancestry.
Jim Moore (j#d#.moore@canrem.com)
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