Salt

Salt is a mineral made mostly of sodium chloride (NaCl). In its granulated form used for cooking, it is often called table salt, while the natural crystalline version is known as rock salt or halite. It is vital for life because it supplies the essential minerals sodium and chlorine, and the taste of saltiness is one of the five basic human flavors. As one of the oldest and most widespread seasonings, salt is known to consistently enhance how food tastes. Methods like salting, brining, and pickling have been crucial for preserving food for centuries.

The earliest known salt processing dates back to around 6000 BC, when people in what is now Romania boiled spring water to extract salt, and a similar operation appeared in China at roughly the same time. Salt was highly valued by many ancient cultures, including the Hebrews, Greeks, Romans, Byzantines, Hittites, Egyptians, and Indians. It became a major trade item, moved by boat across the Mediterranean, along specially built salt roads, and by camel caravans across the Sahara. Because it was scarce and universally needed, salt sparked wars and was used to generate tax revenue—for example, the El Paso Salt War in the late 1860s. It also holds a place in religious ceremonies and other cultural traditions.

Salt is obtained from salt mines or by evaporating seawater or mineral-rich spring water in shallow pools. Its largest industrial use is as a raw material for making chemicals, such as caustic soda and chlorine, which go into products like polyvinyl chloride, plastics, and paper pulp. Of the roughly 300 million tonnes produced globally each year, only a small portion is for human consumption. Other uses include water treatment, de-icing roads, and agriculture. Edible salt comes in forms like sea salt and table salt, the latter often containing an anti-caking agent and sometimes iodine to prevent deficiency. Besides cooking and table use, salt appears in many processed foods.

Sodium is essential for human health, acting as an electrolyte and helping regulate fluid balance. However, too much salt raises the risk of cardiovascular diseases like hypertension. These health effects have been studied for a long time, and many global health organizations and experts in developed countries advise cutting back on salty foods. The World Health Organization recommends adults consume less than 2,000 mg of sodium per day, which equals about 5 grams of salt.

Throughout history, salt availability has shaped civilizations. The first known city in Europe, Solnitsata in Bulgaria, was a salt mine that supplied the Balkans from around 5400 BC. For thousands of years, salt was the best way to preserve food, especially meat. At the Poiana Slatinei site in Romania, evidence shows Neolithic people of the Precucuteni Culture boiled salt-laden spring water using briquetage as early as 6050 BC, and the salt they produced may have fueled a rapid population increase. In China, salt harvesting from Xiechi Lake near Yuncheng dates back to at least 6000 BC, making it one of the oldest verified saltworks.

Animal tissues—like meat, blood, and milk—contain more salt than plant tissues do. Nomads who live on their herds often don’t add salt to their food, but farmers who eat mostly grains and vegetables need to supplement their diet with it. As civilization spread, salt became a key trade commodity. It was highly prized by the ancient Hebrews, Greeks, Romans, Byzantines, Hittites, and others. In the Middle East, salt was used to seal agreements ceremonially, and the ancient Hebrews made a “covenant of salt” with God, sprinkling it on offerings as a sign of trust. An ancient wartime practice was salting the earth—scattering salt over a defeated city to symbolically prevent crops from growing. The Bible recounts King Abimelech doing this at Shechem, and Roman general Scipio Aemilianus Africanus was said to have plowed Carthage and sown it with salt after the Third Punic War, though this story is now considered false.

Salt may have been used as barter in the Neolithic obsidian trade in Anatolia. It was found among funeral offerings in Egyptian tombs from the third millennium BC, along with salted birds and fish. Around 2800 BC, Egyptians began exporting salted fish to the Phoenicians in exchange for cedar, glass, and Tyrian purple dye. The Phoenicians then traded Egyptian salted fish and North African salt across their Mediterranean empire. Herodotus wrote about salt trading routes across Libya in the 5th century BC. During the early Roman Empire, roads were built to transport salt from Ostia to Rome. In Africa, salt served as currency south of the Sahara, with slabs of rock salt used as coins in Abyssinia. The Tuareg have long maintained Saharan routes for salt caravans, known as Azalai, which still cross from southern Niger to Bilma, though much of that trade now continues in reduced form.