Monosodium glutamate, or MSG, is a flavor-enhancing food additive used in Asian cooking and also commonly found in fast foods as well as commercially packaged food products such as chips, crackers, soups and soup mixes, lunch meats, salad dressings and many others.
Some people find that consuming MSG in food can trigger side effects and symptoms including headaches, nausea and others. We'll talk more about MSG side effects in a moment.
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. And basically, 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 — indeed, Asian grocery stores sell sacks of pure MSG, in the form of 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 is almost pure MSG.
MSG in Food
MSG is present in many of the items on the menu at fast-food restaurants, particularly the chicken items. In addition, MSG is also added to commercially packaged food products including:
- Flavored (especially cheese-flavored) chips and crackers
- Canned soups
- Instant noodles
- Soup and dip mixes
- 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.
MSG Side Effects
Some people find that consuming MSG, especially in large quantities, can trigger various side effects and symptoms, including (but not limited to):
- Rapid or irregular heartbeat
- Flushing or excessive sweating
- Skin rash
- Intense thirst
- Lethargy or sleepiness
- Ringing ears
- Tingling in the mouth
What constitutes a large quantity? Per the FDA, it's anything exceeding 3 grams of MSG — or less than a teaspoonful. That's the amount recommended for seasoning up to 5 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.
MSG Safety Concerns
Is MSG safe? That depends, in part, on how you define safe. If your idea of safe doesn't include any of the symptoms described above, then the answer may be no.
Suffer from asthma? The FDA admits that people with asthma may have trouble breathing after consuming MSG (scroll to 4th paragraph from the end). Is that safe? Maybe, maybe not — depending on how high a priority one sets on breathing.
There's more. A 2008 study showed a connection between MSG consumption and obesity. Safe? Again, you decide. But whatever you decide, it surely can't hurt to pay attention to what you're eating, what's in the food you're eating — and how it makes you feel.