Those who are sensitive to monosodium glutamate or trying to avoid it in their food should also be familiar with disodium guanylate. While this food additive doesn't have the same potential adverse effects, it's found in many of the same foods, so it's a good indicator that a food may contain MSG.
Disodium guanylate and MSG are both used to add a meaty or savory flavor to foods. Disodium guanylate is produced by fermentation, usually of tapioca starch, although it can come from other vegetable sources as well. It can be classified under "natural flavors" on a food label, so it isn't always easy to determine if a food contains this additive.
MSG can also give foods a salty flavor without adding as much sodium as would otherwise be necessary. It can be extracted from protein-rich foods, including seaweed, but is usually made through fermentation, like disodium guanylate. It can be made from molasses, starch or sugars. MSG that isn't naturally occurring must be listed as monosodium glutamate on foods labels, but that's not the case when it occurs naturally in ingredients like soy protein isolate or hydrolyzed yeast.
Potential Side Effects
Some people experience adverse effects, such as nausea and headache, after eating foods that contain MSG. The U.S. Food and Drug Administration notes, however, that it hasn't been able to prove that these effects are due to the MSG. Sensitive individuals may experience flushing, palpitations, drowsiness, numbness and tingling when consuming very large amounts of MSG, especially if it is consumed without food. These types of adverse effects aren't typically associated with disodium guanylate.
Disodium guanylate can be used in pasta products, processed vegetables, dairy products, processed fruits, candies, breakfast cereals, processed meat or poultry, fish products, egg products, condiments, alcoholic beverages, energy or sports drinks, soups and sauces.
MSG is often used in Asian food, spice mixes, meat or fish products, salad dressings, dry or canned soups and frozen foods. It's sometimes hidden under another name. Any ingredient containing the words "glutamate," "hydrolyzed," "protein," "protease," "enzymes" or "enzyme modified" is likely to contain hidden MSG, and "yeast extract," "autolyzed yeast," "soy sauce," "Ajinomoto," "calcium caseinate" and "sodium caseinate" also indicate the potential presence of MSG.
As disodium guanylate is relatively expensive, it's usually used in combination with MSG, which is much cheaper to produce. Thus, any foods containing disodium guanylate most likely also have MSG. These two flavor enhancers have a synergistic relationship, and each enhances the action of the other to allow manufacturers to increase the flavor of a food while decreasing the sodium it contains.