nepas provided this very informative article about MSG.

Monosodium Glutamate (MSG)

Many People are concerned about the possible health impact of MSG, a widley used and safe food additive that is derived from a naturally occuring amino acid.  This fact sheet explains what MSG is, where it comes from, and who needs to limit MSG in their diet.

What is MSG?
MSG is a food additive.  Its full name is monosodium glutamate and it comes from the amino acid glutamic acid.  Amino acids are the building blocks of protein; our food and bodies contain protein that, in turn, contains glutamate.  Glutamate is therefore found in a wide variety of foods.

Why is it used?
Glutamate helps enhance the flavor of food, and therefore glutamate is often deliberately added to foods - either as MSG, hydrolyzed protein, or a variety of food ingredients rich in glutamates, such as cheese, tomato pastes, stocks, and sauces.
MSG cannot improve inferior quality food or make up for poor cooking practices.  It does not allow a cook to substitute low-quality for high-quality ingredients in a recipe, and does not tenderize meat.  MSG simply enhances the savory flavors already present in food.

Where does it come from?
Glutamate is found in abundance in virtually all natural foods - from meat, poultry, fish, cheese, and milk (including human breast milk) to tomatoes, mushrooms, and many other vegetables.  Glutamate is the most commonly found amino acid in nature, the average diet provides between 10 grams to 20 grams of bound glutamate (bound in protein) and 1 gram of free glutamate (not bound in protein).  Glutamate can also be manufactured as MSG.

How is it Made?
Japanese cooks for the past 1000 years have known that certain foods taste better when prepared with a soup stock made from a type of seaweed - Laminaria japonica.  But it was only in 1908 that Japanese scientists identified what it was in the seaweed that was enhancing the flavor, creating monosodium glutamate or MSG.  Like many foods today monosodium glutamate is produced through fermentation, a process used in making beer, vinegar, soy sauce, and yogurt.  The process begins with natural products such as molasses from sugar cane or sugar beets and food starch from tapioca or cereals, which are fermented in a controlled environment.

Is MSG different from glutamate?
The human body treats MSG the same as natural glutamate found in food.  For instance, the body does not distinguish between free glutamate from tomatoes, cheese, or mushrooms and the glutamate from MSG added to foods.  Glutamate is glutamate, whether naturally present or from MSG.

Is it high in sodium?
No, MSG contains only one-third the amount of sodium as table salt (13% vs 40%) and is used in much smaller amounts.  That said, the sodium in MSG needs to be taken into account when sodium levels in food are considered.

Is it safe?
Yes.  MSG is one of the most extensively researched substances in the food supply and has been studied for more than forty years.  Numerous international scientific assessments have been conducted involving hundreds of studies.  None of these have conclusively linked MSG to asthma or the infamous 'Chinese Restaurant Syndrome'.
Even though there is no convincing evidence that MSG is a significant factor in causing systemic reactions resulting in severe illness or mortality, a very small number of people who are sensitive to a range of foods, especially those with asthma, may be sensitive to glutamate.

How do I know if MSG is in a food?
If MSG is used in food or meat products, it must be declared on the label within the ingredient statement.  It is typically declared as "MSG" or "monosodium glutamate" in the ingredient statement.
There is no requirement in restaurants to declare the presence of MSG in the products sold.  If you believe you are sensitive to them you should ask if they are being used.  The restaurant should be able to tell you whether they are used.  Sensitive individuals should also be aware that high amounts of glutamates may be present naturally in certain food.

MSG Is An Ingredient That May Cause Allergen-Like Reactions
Certain food intolerances can cause reactions which do not involve the immune system.  These problems are caused by an abnormality in the metabolism of a particular food component.  Lactose intollerance is an example where susceptible individuals do not metabolize lactose normally.  In this case, there is no immune system response, thus it is not an allergic reaction.
In January, 2006, the U.S. Food and Drug Administration (FDA) implemented the Food Allergen Labeling and Consumer Protection Act (FALCPA), requiring food labels to indicate if the product contains any of the "Big 8" allergens.  The FALCPA identified the eight major food ingredients as allergens that account for 90% or more of food allergies.  The "Big 8" allergens include:
  • Milk
  • Eggs
  • Fish(such as bass, flounder, or cod)
  • Crustacean shellfish(such as crab, lobster, or shrimp)
  • Peanuts
  • Tree Nuts(such as almonds, pecans, or walnuts)
  • Wheat
  • Soybeans
It is known that there are many foods and food ingredients to which some individuals may have some degree of intolerance or possible allergic reaction.  If you recall, FSIS Notice 45-05 (Verification ofActivities Related to an Establishment's Controls for the Use of Ingredients of Public Health Concern) directed FSIS inspection program personnell to be aware of the "Big 8" allergen food ingredients, as well as other ingredients.
These other ingredients that may cause potential adverse reactions in sensitive individuals were identified as monosodium glutamate(MSG), sulfites, lactose, and Yellow 5(tartrazine).  The adverse reactions to these substances are due to the ingredient itself or its chemical composition.  Therefore, although MSG is not declared a true allergen, it is highly recommended that MSG be handled in the same fashion as an allergen ingredient.

Commercial Form of MSG
MSG is commercial retailed in grocery stores with the product name "Accent" and it is sold in the spice aisle.  Another retail product name is mei yen.