Pique the Geek 20100613. The Things that We Eat: Salt

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Contrary to some popular opinion, salt is an essential part of the diet.  Unfortunately, it is possible to get too much of a good thing, and that is true in the case of salt.

On the other hand, it is possible to become deficient in salt, although that is quite rare with a modern western diet.  However, vegans and other vegetarians can become deficient, especially when performing strenuous work in hot weather, since sweat is about 0.9% salt.

That 0.9% is not by accident.  By far the most common mineral in the human body, sodium and chloride amount to most of the minerals in blood plasma, with lesser amounts of others, potassium being the next most common metal ion.  The total concentration of minerals in plasma has the same osmotic activity as a 0.9% salt solution, so that is why normal saline solution is used in intravenous situations.  Pure water or water saltier than 0.9% causes irritation.  Think of using eye drops versus plain water in the eyes.  Plain water stings a bit, whilst eye drops do not.  Such solutions are called isotonic.

Salt is a remarkable material.  For one thing, it is the only rock that we eat.  As a matter of fact, it is the only pure inorganic substance, other than water, that we commonly use for nourishment.  Salt is derived from rocks, the minerals in which dissolve over the ages and make their way to the sea.  Most commercial salt deposits are the result of ancient saltwater deposits.

Salt has an extremely long history, and the Latin word for salt, sal, shows up in many modern English words.  “Salary” refers to the practice in Rome of paying the military partly in salt, later replaced with an allowance in money to buy it.  “Salad” refers to a mixture of vegetables, the flavor of which in enhanced with the addition of dressings often fairly high in salt.  “Sauce” is also derived from the same root, and most sauces are indeed salty.

Salt has been regarded as so essential that those that had it often jealously protected their sources because it was a sure income producer.  Throughout history various governments have taxed salt, causing it to be highly adulterated, often with chalk or other light colored mineral substances.  The phrase “as in salt that has lost its savor” from the Bible refers to this highly debased material.

Saltiness is one the five basic tastes recognized by taste buds in humans.  Thus, it obviously is important for survival.  The others are sweetness, sourness, bitterness, and ugami.  All except bitterness are “positive” tastes when not too intense, meaning that we experience pleasure from those tastes.  Bitterness is a negative taste, a defensive mechanism to protect us from eating bitter substances, many of which are bitter because of toxic alkaloids in plants.

Except for the relatively rare situations where we get too little salt, such as dehydration (with electrolyte loss) from vomiting and diarrhea, excessive sweating from hard word in hot conditions, or other similar situations, we run into trouble by getting too much salt.  Our bodies try very hard to keep the 0.9% concentration in the plasma.  By the way, symptoms of too little salt include muscle cramps which can also be caused by too little potassium.  The reason is that both of those ions are essential for nerve impulses to be transmitted, and lack of them cause misfires.

Most estimates indicate that a healthy adult requires around one gram of salt per day from all sources of intake.  That is not very much, a little under a quarter of a teaspoon.  Diets high in processed foods are very much higher, sometimes exceeding 10 grams per day.  Why are processed foods so high in salt?  There are several reasons.

First, salt is now extremely cheap, a relatively recent historical development, so it makes an economical additive to many foods.  Second, since we perceive salt as pleasant, manufacturers add it to sell more product.  Third, salt is a flavor enhancer for other flavors and scents.  Food smells seem stronger in the presence of even low amounts of salt, which is why it is often added in small amounts to things like ice cream and other sweet dishes.  Forth, salt masks the bitter sensation to a fairly large extent.  Dishes containing bitter greens, for example, are quite unpalatable without added salt, becoming delicious when salted.  Finally, consumer demand is the largest factor.  People just like salt in most of their food.  If food processors could not sell their product because of high salt content, they would lower it.

There has been a controversy for many years linking high salt intake to hypertension (high blood pressure).  It turns out that the link is much weaker than previously thought, and only in some people.  A low sodium diet makes no difference in blood pressure levels in most people, but is helpful for a few.  Genetics seems to play a much larger role than sodium intake.

It is possible to wean oneself off of high salt dietary levels, but it takes time.  One of the easiest ways is, and this sounds counterintuitive, to salt food adequately during the preparation phase.  One of my sons is in culinary school and tells me that research shows that people tend to add up to five times more salt at the table if the food is not adequately salted during preparation than they do if it was adequately salted.  Another trick is to taste your food before you salt it.  It is amazing how much salt is added from the habit of loading it up before tasting, when it would be just fine without any more salt.

Salt substitutes are available, some based on potassium chloride, some on citric acid (lemon pepper, for example), and some using larger than usual amounts of herbs to add flavor (remember, salt increases the sensation of scent, so to make up for less salt, you have to use more scent).

Several jurisdictions are proposing limiting the amount of salt in food, especially processed food.  I am not in favor of that proposal for several reasons, not the least of which is a personal freedom argument.  Since the hypertension like is weak, that is not a very good argument, and folks sensitive to salt already know it if they have medical care.  However, I am all for labeling processed foods so it is easy to tell how much salt is in it, so that a person can make an informed decision.

This short post has not even scratched the surface of salt, since 83% of the salt produced is industrial, not food, grade.  Salt is, along with water, coal, oil, gas, and air one of the basic materials for the chemical industry.  Also, many tons are used annually for deicing roadways.

Well, you have done it again.  You have wasted many einsteins of perfectly good photons reading this bland post.  And even though Bill Krystol ceases to be snide when he reads me say it, I always learn much more than I could possibly hope to teach writing this series, so please keep the comments, questions, corrections, and other issues coming.  Remember, no scientific or technical issue is off topic in the comments here.  I will stay around for a while for Comment Time tonight, and be back during Review Time tomorrow around 8:00 PM Eastern.

Warmest regards,

Doc

Crossposted at Dailykos.com