Monosodium glutamate (MSG) - Questions and Answers - Canada.ca Monosodium glutamate (MSG) is the sodium salt of the naturally occurring amino acid, glutamic acid which makes up 10 to 25 % of all food protein, from both animal and vegetable sources. In addition to being an ingredient intentionally added to foods, glutamate occurs as a natural part of proteins, including vegetable and animal proteins.