Salt
From Memory Alpha, the free Star Trek reference.
Salt, known chemically as sodium chloride (NaCl), is an essential chemical compound, vital for Earthly life. It is responsible for the salinity of bodily fluids, and is important for the balance of electrolytes. It is also the most common spice in the galaxy. (VOY: "Prototype")
In 2266, the USS Enterprise visited M-113 for routine medical examinations of the scientists working there. Ultimately, one of the scientists was revealed to be a species native to that arid world, a creature that required large quantities of salt to survive. This creature could draw the body salts from other beings to sustain itself, a process that was fatal to its victims. (TOS: "The Man Trap")
Salt is a popular addition to food and is used by Humans, Bolians and other species. Starfleet ration packs carry salt. (DS9: "Nor the Battle to the Strong", "Waltz")
In 2369, Commander Benjamin Sisko and Ilon Tandro compared the Trill and their symbionts to salt added to water. (DS9: "Dax")
In 2374, B'Elanna Torres said that with a little sodium chloride, the silver blood would probably taste a lot like Neelix' soup. (VOY: "Demon")
