Monosodium Glutamate (MSG) is a food additive used as a flavor enhancer. It is common in fast foods, snacks, canned, and frozen foods where it restores or enhances flavors that processing has damaged or destroyed. It is also used in non-processed food, often in its naturally occurring form, to heighten flavor. MSG is based on an amino acid called glutamate, which is stabilized with salt (the monosodium part of the name). It was first isolated in Japan about a century ago and was introduced into the United States after the Second World War. American soldiers had noticed how much tastier Japanese military rations were than their own.