Water in food can cause microorganisms to grow, which makes the food more likely to spoil. Using natural preserving agents such as sugar and salt, the water available can be chemically reduced and, as such, prevent the spread of microorganisms. People have used salt to preserve meat, fish and vegetables since agriculture first began.
Essential to life, but in minute quantities, mankind has been consuming salt since Neolithic times. It is used both as a preservative and a condiment. Until the 19th century, salt was a rare resource, as it was geographically poorly distributed. In the 20th century, it became an inexpensive industrial product, added to most foodstuffs in the food industry. Nowadays, it is consumed in excess and widely criticised because of health risks.