Kathleen Holton is a professor in the School of Education, Teaching and Health and the Center for Behavioral Neuroscience at American University in Washington, D.C. Her research examines the negative effects of food additives on neurological symptoms, as well as the positive, protective effects of certain micronutrients on the brain. She is working on a book about how people can avoid consuming food additives and test themselves for sensitivity. She contributed this article to Live Science's Expert Voices: Op-Ed & Insights.
A recent video from the American Chemical Society purporting to debunk myths about the food additive monosodium glutamate (MSG) led to a slew of news stories — but that coverage failed to recognize that a subset of the population should avoid MSG.
The video contains two misleading facts. The first suggests MSG is considered "Generally Recognized as Safe," or GRAS. The GRAS label for additives gives the appearance of safety; yet the term GRAS was simply given to food additives that were in use when the Food Additives Amendment of 1958 was established. The label effectively "grandfathered in" the additives so they could bypass premarket approval by the FDA (i.e., safety testing). Secondly, the video states that free glutamate occurs naturally in some foods. This is true; however, it does not mean that MSG is safe for everyone. People who are sensitive to MSG must also avoid foods with high amounts of naturally occurring free glutamate, such as soy sauce and Parmesan cheese.
How MSG works
MSG is a flavor enhancer that has been used in processed foods in the United States since after World War II. Though many associate MSG with Chinese food, people are more likely to encounter MSG in foods like soup, broth, chips, snacks, sauces, salad dressings and seasoning packets. The active part of MSG, which imparts its "umami" flavor, comes from the glutamate portion of the compound. Glutamate is an amino acid commonly found in the diet in bound form (connected to other amino acids to form a full protein, like meat) and free form (where glutamate is no longer bound to a protein). It is this free form of glutamate (like that found in MSG) which has the ability to act as a flavor enhancer in food by exciting the neurons in your tongue.
Glutamate can always be considered a "natural flavor" because it is produced by dissociating a naturally occurring protein into its individual amino acids. Additives containing free glutamate are created by simply disrupting any protein's structure through hydrolyzation, which frees glutamate (and other amino acids), allowing glutamate to enhance the flavor of food by stimulating the neurons on your tongue.
Who needs to avoid MSG?
As researchers, we don't yet know what percentage of the population is sensitive to MSG. But we do know enough to confirm that the amino acid glutamate, when in its free form (i.e., when it is not bound to a full protein like meat) causes negative reactions in certain people. An individual's reaction to MSG is not limited to Chinese Restaurant Syndrome (CRS), which is characterized by symptoms like headache, sweating, rapid heartbeat and tightness in the chest. These symptoms usually occur within minutes of eating the compound, often while the diner is still in the restaurant.
In my research on the effects of MSG in individuals with irritable bowel syndrome and the chronic pain condition fibromyalgia, I observed headache (including migraine), diarrhea, gastrointestinal pain and bloating, extreme fatigue, muscle pain and cognitive dysfunction — all of which improved when subjects were put on a diet low in free glutamate, and which returned with re-introduction of MSG. (This was a double-blind, placebo-controlled study). In contrast to CRS, symptoms in fibromyalgia patients tend to begin somewhat later, hours after ingestion, making it more difficult for these people to identify the food-related trigger.
Other researchers are studying the potential effects of MSG on conditions like migraine, temporomandibular joint disorder (TMD/TMJ), obesity and Type 2 diabetes. Researchers from the University of North Carolina at Chapel Hill recently found an association between high consumption of MSG and the prevalence of overweight adults in China. Understandably, the glutamate industry is hotly contesting these and other findings related to MSG and obesity. Consumers should know that the glutamate industry funded the majority of studies "proving" the safety of MSG. Independent scientists have not always agreed with those findings.
In addition to MSG, free glutamate can also be found in other food additives, including any hydrolyzed protein, protein isolate, protein extract and autolyzed yeast extract, just to name a few. Food manufacturers can use these additives in a product, and still label the food as not containing MSG, since the chemical structure is different. That is, the structure does not contain the sodium part to form monosodium glutamate. However, the effect of the free glutamate is the same as that of MSG (both in its flavor-enhancing ability as well as its ability to cause symptoms in sensitive individuals).
Glutamate is not only an amino acid in the diet, it is also an important neurotransmitter essential for the optimal functioning of our nervous systems. However, too much of this chemical can cause things in our bodies to go awry. It is well established that high amounts of glutamate can cause "excitotoxicity," where neurons get over-excited to the point that they die.
For example, because of the consistent research on the excitotoxic effects of MSG on the brains of young animals in the 1960s, researchers testified before the U.S. Congress about the danger of using MSG in baby food. As a result, MSG was voluntarily removed from baby foods in 1969.
The million-dollar question is: Does everyone react to these additives? No, some people can consume relatively high amounts of free glutamate without any symptoms. However, research shows that a subset of the population is sensitive and can benefit from avoiding MSG (and other sources of free glutamate) in food.
If a person is suffering from unexplained symptoms like headache, bowel disturbance, fatigue, cognitive dysfunction, or pain that lacks a structural explanation, they may want to try avoiding free glutamate in all its forms. The only way to test for sensitivity is by avoiding excess free glutamate for a period ranging from two weeks to a month. One can do this by eating whole, non-processed foods, using whole herbs and spices, making marinades and salad dressings from scratch, and avoiding foods which naturally have higher amounts of free glutamate, like soy sauce, fish sauces, Parmesan and other aged cheeses, and large amounts of tomato sauce.
The moral of the story is simple: Blanket statements like "MSG isn't bad for you" are misguided — they give a false perception of safety to a compound that not everyone should be consuming.
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