While there are many different chemicals falling into the
category termed "salts" by chemists, to laypeople "salt"
means sodium chloride. That's the salt that we crave, season our food with,
consume too much of, and get sick from. Today, salt comes from a salt-shaker on
every dining table and ultimately from a supermarket, is cheap, and is
available in essentially unlimited quantities. Our bodies' main problem with salt
is to get rid of it, which we do copiously in our urine and in our sweat. The
average daily salt consumption around the world is about 9 to 12 grams, with a
range mostly between 6 and 20 grams (higher in Asia than elsewhere).
Traditionally, though, salt didn't come from salt-shakers
but had somehow to be extracted from the environment. Imagine what the world
used to be like before salt-shakers became ubiquitous. Our main problem with salt
then was to acquire it rather than to get rid of it. That's because most plants
contain very little sodium, yet animals require sodium at high concentrations in
all their extracellular fluids. As a result, while carnivores readily obtain
their needed sodium by eating herbivores full of extracellular sodium,
herbivores themselves face problems in obtaining that sodium. That's why the
animals that you see coming to salt licks are deer and antelope, not lions and
tigers. Human hunter-gatherers who consumed much meat, such as the Inuit and
San, thus met their salt requirement readily, though even their total salt
intake was only 1 or 2 grams per day because much of their prey's sodium-rich
blood and other extracellular fluids became lost in the course of butchering
and and cooking. Among traditional hunter-gatherers and farmers consuming a
diet high in plant food and with limited meat, those living on the seacoast or
near inland salt deposits also have easy access to salt. For instance, average
daily salt consumption is around 10 grams among the Lau people of the Solomon Islands,
who live on the coast and use salt water for cooking, and also among Iran's
Qashqa'i nomadic herders, whose homeland has natural salt deposits on the
surface.
However, for dozens of other traditional hunter-gatherers and farmers whose daily salt intake has been calculated, it falls below 3 grams. The lowest recorded value is for Brazil's Yanomamo Indians, whose staple food is low-sodium bananas, and who excrete on the average only 50 grams of salt daily: about 1/200 of the salt excretion of the typical Americans. A single Big Mac hamburger analyzed by Consumer Reports contained 1.5 grams (1,500 milligrams) of salt, representing one month's salt intake for a Yanomamo, while one can of chicken noodle soup (containing 2.8 grams of salt) represents nearly two months of Yanomamo salt consumption. A possible record was set by a Chinese-American restaurant near my home in Los Angeles. Its double pan-fried noodles combo dish was reportedly analyzed as containing one year and three days' worth of Yanomamo salt intake: 18.4 grams.
Hence traditional peoples crave salt and go to great lengths
to obtain it. (We, too, crave salt: just try eating nothing but fresh,
unprocessed, unsalted food for one day, and then see how wonderful salt tastes
when you finally sprinkle some on your food.) New Guinea Eastern Highlanders with
whom I have worked, and whose diet consists up to 90% of low-sodium sweet potatoes,
told me of the efforts to which they used to go to make salt a few decades ago,
before Europeans brought it as trade goods. They gathered leaves of certain
plant species, burned them, scraped up the ash, percolated water through it to
dissolve the solids, and finally evaporated the water to obtain small amounts
of bitter salt. The Dugum Dani people of the Western New Guinea Highlands made
salt from the only two natural brine pools in their valley, by plunging a spongy
piece of banana trunk into a pool to soak up brine, removing the piece and
drying it in the sun, burning it to ash, and then sprinkling water on the ash
and kneading the moist mass into cakes to be consumed or traded. After all that
traditional effort to obtain small quantities of impure bitter-tasting salt,
it's no wonder that New Guineans eating in Western-style cafeterias can't
resist grabbing the salt-shaker on the dining table and letting the stream of
pure salt run out onto their steaks and salads at every meal.
With the rise of state governments, salt became widely
available and produced on an industrial scale (as it still is today) from
salt-water drying pans, salt mines, or surface deposits. To its use as a
seasoning was added its use, reportedly discovered in China around 5,000 years
ago, to preserve food for storage over the winter. Salt cod and salt herring
became fixtures of the European diet, and salt became the most traded and most
taxed commodity in the world. Roman soldiers were paid in salt, so that our
word "salary" for pay is derived not from the Latin root for
"money" or "coins" but from the Latin root for
"salt" (sal). Wars were fought over salt revolutions; revolutions
broke out over salt taxes; and Mahatma Gandhi rallied Indians against the
perceived injustice of British colonial rule by walking for one month to the
ocean, violating British laws by illegally making salt for himself on the beach
from the freely available salt water, and refusing to pay the British salt tax.
As a result of the relatively recent adoption of a high-salt
diet by our still largely traditional bodies adapted to a low-salt diet, high
salt intake is a risk factor for almost all of our modern non-communicable
diseases. Many of these damaging effects of salt are mediated by its role in
raising blood pressure. High blood pressure (alias hypertension) is among the
major risk factors for cardiovascular diseases in general, and for strokes,
congestive heart disease, coronary artery disease, and myocardial infarcts in
particular, as well as for Type-2 diabetes and kidney disease. Salt intake also
has unhealthy effects independent of its role in raising blood pressure, by
thickening and stiffening our arteries, increasing platelet aggregation, and
increasing the mass of the heart's left ventricle, all of which contribute to
the risk of cardiovascular diseases. Still other effects of salt intake
independent of blood pressure are on the risks of stroke and stomach cancer.
Finally, salt intake contributes indirectly but significantly to obesity (in
turn a further risk factor for many non-communicable diseases) by increasing
our thirst, which many people satisfy in part by consuming sugary high-calorie
soft drinks.
(Jared Diamond, ‘The World until Yesterday)
