MSG, or monosodium glutamate, is one of the most fascinating substances on earth. It occurs throughout nature and is an essential ingredient in almost all the foods we eat. But it’s also the subject of enormous controversy, boycotts and bans. The story of its invention and discovery is remarkable enough, but its subsequent history is even more eventful. It’s difficult to think of a substance that has been more unfairly vilified, and yet it also feels like it’s on the verge of a revival.

This series of four articles traces the story of this humble amino acid, from its discovery in early twentieth-century Japan, through its adoption throughout Asia, to its brush with controversy in mid-century America, and finally up to its twenty-first-century renaissance.