Answer
Carnivores get enough salt (sodium chloride) from the meat they consume, but herbivores don't get and adequate amount of salt from their diet because plant food contains very little salt. Therefore, humans must ingest salt in their food.
Originally, in early evolutionary times, humans were carnivores; later they became half carnivores and half herbivores as ecological conditions changed.
In time, by experimentation men became successful agriculturists, and came to depend on plants for most of their food. One result of this change in diet was that man/woman needed to take supplemental salt with his/her food. This imperative need for salt made salt very valuable, and it became not only a valuable food item, but was used as an economic instrument that embodied economic/monetary value, and could be utilized as a means of exchange
in commerce/business. The word "salary" comes from "salt" and in the ancient past salt was used to pay salaries/wages, and to redeem debts.
Salt ( Na+ CL-) is of great physiological importance, but it is hard to get from a vegetarian diet. This physiological need for salt and the relative difficulty of obtaining enough from a vegetarian diet results in our strong desire and craving for salt.
Salt or "salty" is one of the five basic/primary tastes and we have special taste buds for this flavor. If humans are raised on food with little salt, they can enjoy food with very little or no salty taste. But people in western societies, who have been raised on food seasoned with salt, find food without salt to be tasteless and unenjoyable. There is, however, a salt consumption problem in the US society-- and probably in most of western countries. We consume too much salt, and this has several negative health consequences.
Work Step by Step
The RDA for salt (NaCL) is 1.1 mg/day, but the typical US diet contains about 4.5 mg/day. This consumption of excess salt is due to the large amount of processed foods eaten by Americans. In processed foods like soy sauce, monosodium glutamate (MSG), baking soda, baking powder, and tomato ketchup, many canned foods, the salt is hidden, and we scarcely realize how much salt gets into our food when we use these preparations.
