Salt was the first seasoning used by our ancestors. They got it by evaporating seawater, or by mining it. The origin of salt deposits in the ground can also be traced back to oceans which no longer exist so that basically all salt is "sea salt." Salt was mined near Salzburg ("City of Salt") in Austria as early as 6500 BC and the ancient Romans built large evaporation ponds by the sea to collect salt. In fact, the Romans prized salt so much that soldiers were given a special allowance, known as the "salarium" to purchase it. (Fun fact: the word “salary”, of course, derives from this Latin expression.)
It wasn't only for its taste that salt was so prized. It was also for its preservative value. When the salt concentration outside a bacterial or fungal cell is higher than inside it, water is drawn out of the cell to reduce the outside salt concentration. This process of "osmosis" dehydrates the cell and eventually destroys it. Meat used to be preserved by soaking it in a brine solution or by covering the surface with whole grains of salt which were known as "corn," hence the origin of corned beef.
Whether we are talking about table salt, kosher salt, sea salt or Himalayan salt, we are talking about a substance that is at least 98% sodium chloride. The differences lie in the size and shape of the grains and the trace impurities they contain. (To see the different sizes of salt grains, check out Ada McVean’s article on our website showing microscopic photos of sea salt vs table salt). Sea salt is made by evaporating seawater, table salt is refined from salt mined around the world, Himalayan salt is mined in the Punjab region of Pakistan, and kosher salt may come from seawater or from mines.
Let’s deal with kosher salt first. This is not salt that has been specially blessed in any way or has undergone any sort of ritualistic processing. The name comes from its use in draining blood from meat. According to Jewish dietary laws, based on Leviticus 7:26 ("You shall not eat any blood, whether that of fowl or of beast, in any of your dwellings"), blood has to be removed from butchered meat before it can be consumed. Rubbing the surface of the meat with salt draws moisture to the surface and large coarse grains do this better than small grains which tend to dissolve into the meat. The shape of the salt crystals is determined by how the salt is processed, for example, the rate at which water is allowed to evaporate from a salt solution. In general sea salt tends to have larger grains. Because there is more air space between large crystals, it takes fewer to fill a teaspoon. A teaspoon of kosher salt actually has a little less salt than a spoonful of table salt, so that in cooking, more will have to be used to achieve the same taste. However, when sprinkled on dry foods, such as French fries, you need less kosher or sea salt because the larger crystals make better contact with taste buds.
These differences, though, are hardly significant in terms of monitoring sodium intake which is very important because excess sodium is linked with high blood pressure. A quarter teaspoon of table salt has about 590 mg of sodium, coarse sea salt 580 mg, and kosher salt around 480 mg. In the context of the overall diet, which should have no more than 2300 mg of sodium, the difference in sodium content of the different salts is irrelevant.
“Himalayan salt,” which is composed of large grains of rock salt mined in Pakistan, is touted as a healthier version because it contains traces of potassium, silicon, phosphorus, vanadium, and iron. The amounts are enough to add colour to the crystals, giving them a more “natural” appearance, but are nutritionally irrelevant. Some promoters make claims that are laughable. Himalayan salt, they say, contains stored sunlight, will remove phlegm from the lungs, clear sinus congestion, prevent varicose veins, stabilize irregular heartbeats, regulate blood pressure and balance excess acidity in brain cells. To delve further into these unsubstantiated (and quite frankly ridiculous) claims, feel free to check out our “Is Himalayan Pink Salt Better For You?” piece on our website.
Another line of attack vilifies table salt for its additives and for being dried at a temperature that “radically and detrimentally alters the chemical structure of the salt.” Salt is composed of sodium and chloride ions and once dissolved has no “chemical structure.” As far as additives go, small amounts of ferrocyanide, phosphates or silicates are used to ensure easy pouring, and potassium iodide is added to supply the body with the iodine the thyroid gland needs to synthesize its hormones. Indeed, in North America, goiter due to iodine deficiency has been virtually eliminated. Although potassium iodide is relatively stable, it does slowly react with oxygen to yield iodate. A small dose of sugar added to salt serves to protect the iodide by reacting with oxygen and in a sense sacrificing itself to prevent iodide from being oxidized.
The bottom line here is that the type of salt used is not important but the amount used is. And remember that the salt added from a salt shaker makes up only about 15% of our total intake. Processed foods, like salami, is the real problem. Indeed, the word salami derives from the Latin meaning "salted things." And we eat way too many salted things.