What is MSG? (Monosodium Glutamate)

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Monosodium glutamate, or MSG, is a flavor-enhancing food additive used in Asian cooking. It's also commonly found in fast foods and commercially packaged food products like chips. Some people find that consuming MSG in food can trigger side effects and symptoms including headaches, nausea, and others. 

MSG is derived from an amino acid called glutamic acid, which occurs naturally in foods such as mushrooms, aged parmesan cheese and fermented soybean products like soy sauce. Glutamic acid belongs to a broad category of compounds called glutamates, which are the source of a flavor called umami.

MSG and Umami

Variously described as "savory," "meaty" or "earthy," umami has come to be recognized as the fifth taste, in addition to sweet, salty, sour and bitter. Glutamates such as MSG taste like umami, or more accurately (just as sugar is sweet and lemons are sour), glutamates are umami.

In addition to its own distinctive taste, umami also has the property of enhancing other flavors by imparting a depth and fullness to them. Therefore, since MSG is a synthetic glutamate, adding MSG to food does two things: It adds umaminess, while also enhancing and intensifying other tastes, in particular, the salty and sour ones.

Cooking with MSG

MSG was invented by isolating the glutamic acid in the seaweed used in making the traditional Japanese broth kombu dashi. And while glutamates occur naturally in everything from meat and milk to corn and wheat, MSG is strictly a food additive.

In Asian cuisines, MSG is used as a seasoning during cooking this is why Asian grocery stores sell sacks of pure MSG. It comes as a crystalline white powder, which is then sprinkled into stir-frys and other preparations. Latin American and Caribbean cuisines also incorporate MSG, particularly in spice rubs. And in the U.S., accent flavor enhancer are almost always pure MSG.

MSG in Food

MSG is present in many of the items on the menu at fast-food restaurants, particularly in chicken dishes. MSG is also added to many commercially packaged food products including:

  • Flavored (especially cheese-flavored) chips and crackers
  • Canned soups
  • Instant noodles
  • Soup and dip mix
  • Seasoning salt
  • Bouillon cubes
  • Salad dressings
  • Gravy mixes or pre-made gravies
  • Cold cuts and hot dogs, including soy-based (i.e. vegetarian) varieties

Also, note that not all packaged foods containing MSG will explicitly say so on the label. Ingredients like hydrolyzed protein, autolyzed yeast, and sodium caseinate are all pseudonyms for MSG. People who have an allergy or sensitivity to MSG should be vigilant for these kinds of naming conventions.

MSG Side Effects

MSG is "generally recognized as safe" or GRAS by the FDA but that doesn't mean it's safe for everyone. Some people have a sensitivity to it in large quantities while other people have a full allergy to it. If you can not consume glutamate then you should avoid MSG as well. It's believed that most people do not have a reaction to MSG.

Some people find that consuming MSG, especially in large quantities, can trigger various side effects and symptoms, including (but not limited to):

  • Headaches
  • Nausea
  • Dizziness
  • Rapid or irregular heartbeat
  • Flushing or excessive sweating
  • Skin rash
  • Numbness
  • Intense thirst
  • Lethargy or sleepiness
  • Ringing ears
  • Tingling in the mouth

What constitutes a large quantity? Per the U.S. Food and Drug Administration, it's anything exceeding three grams of MSG or less than a teaspoonful. That's the amount recommended for seasoning up to five servings of fried rice, or about a pound of meat. But with such small measurements, it's easy to see how a busy restaurant cook could accidentally go a little overboard.