Studies from as far back as 1991 show that salt activates the same neurological pathways that narcotics do, triggering the brain's "pleasure center."

Unlike sugar, which all babies love from birth, salt is an acquired taste. Kids who are exposed to salty foods before six months start to prefer salted over unsalted foods, while kids who aren't exposed don't. Today, more than three-quarters of Americans' weekly salt intake comes from processed foods.

And to manufacturers, salt isn't just salt; food producer Cargill sells 40 different types with different chemical structures. Each one is optimized for certain uses, and they have fun names like "Special Flake," "Fine Flake Improved," and "Shur-Flo Fine Flour Salt."