Monosodium Glutamate: Flavor, Industry, and Controversy

Monosodium glutamate (MSG) is one of the most ubiquitous food additives in the modern world. It is a sodium salt of glutamic acid, an amino acid naturally present in foods like tomatoes and seaweed. In isolation, MSG delivers the savory quality known as umami, which food scientists and chefs alike recognize as the “fifth taste.” While it was first isolated in Japan in the early 20th century, its widespread adoption truly accelerated after World War II, when American food manufacturers, the military, and the burgeoning fast-food industry recognized its ability to cheaply enhance flavor in otherwise bland, mass-produced food.

The Molecule and the Brain

At its core, MSG is simply glutamic acid (an amino acid) bound to a sodium ion, which makes it soluble and easy to sprinkle into foods. The problem arises not from sodium itself, but from the glutamate. Glutamate is one of the brain’s most important neurotransmitters—it excites neurons, allowing them to send signals. To regulate this, the brain uses glutamate receptors (including NMDA and AMPA receptors), which act as “gates” for communication.

When too much glutamate overstimulates these receptors, neurons can become damaged or even die. This process is called excitotoxicity. MSG, when consumed in significant amounts, can raise glutamate levels in the blood and—according to critics like Dr. Russell Blaylock—may overwhelm the brain’s natural protective barriers. This overstimulation can lead to neurological stress and may be linked to headaches and migraines, dizziness, visual disturbances, or even difficulties in speech such as stuttering. The same mechanism that makes MSG enhance flavor on the tongue—its ability to strongly activate glutamate receptors—can, in sensitive individuals, become a double-edged sword for the nervous system.

Widespread Adoption by Industry

The commercial and fast-food industries quickly embraced MSG because it was inexpensive, easy to use, and dramatically improved the palatability of processed foods. By the 1950s and 1960s, MSG was found in soups, frozen dinners, canned vegetables, potato chips, ketchup, salad dressings, seasoning packets, and nearly every corner of the emerging fast-food sector. Its use became so ubiquitous that it was virtually invisible to the public—listed on labels but rarely questioned. To further obscure its presence, MSG was often hidden behind terms like hydrolyzed protein or yeast extract, as well as other seemingly harmless labels such as natural flavoring, spices, autolyzed yeast, and textured protein. These umbrella terms allowed manufacturers to include MSG or related glutamate compounds without openly naming them, making it difficult for consumers to know when they were actually eating it.

Behind this expansion was a strategic push. After World War II, the U.S. Army reportedly held closed-door meetings with representatives of the food industry to discuss how to improve the appeal of military rations and mass-produced foods for both soldiers and civilians. MSG, with its uncanny ability to stimulate the palate and make otherwise bland rations taste rich and meaty, was promoted as a solution. This collaboration between the military and food corporations seeded the broader use of MSG in the postwar American diet, paving the way for its integration into mainstream food production.

Excitotoxins and Health Concerns

Despite its usefulness to manufacturers, MSG has long been controversial. The term excitotoxins refers to a class of chemicals—including MSG—that overstimulate nerve cells, leading to damage or death. Neurosurgeon Dr. Russell Blaylock’s 1994 book Excitotoxins: The Taste That Kills brought this issue into public consciousness. Blaylock argued that MSG, along with aspartame and other excitotoxins, can overstimulate brain cells to the point of toxicity. He warned that regular exposure may contribute to neurodegenerative diseases, impaired brain function, and long-term cellular damage.

MSG Symptom Complex

Even before Blaylock’s warnings, consumers reported acute reactions to MSG. Popularly referred to as “Chinese Restaurant Syndrome” in the 1960s (a problematic label that unfairly singled out Chinese cuisine), these symptoms included headaches, flushing, sweating, chest tightness, palpitations, dizziness, nausea, and weakness. Today, the condition is often described more neutrally as MSG Symptom Complex. While some studies have downplayed these complaints, anecdotal evidence remains abundant, and many individuals experience reproducible symptoms when consuming MSG-laden foods. According to Blaylock and other critics, these are not simply unpleasant side effects but signals of underlying cytotoxic and neurotoxic processes.

A Contested Legacy

The scientific establishment has often defended MSG, pointing to studies that suggest it is safe in moderate amounts. Yet critics argue that much of the research downplaying risks has been industry-funded, echoing patterns seen in the sugar, tobacco, and trans-fat industries. MSG’s ability to alter how the brain perceives flavor has also raised questions about its role in food addiction and overeating—making calorie-dense processed foods far more palatable than their natural ingredients would otherwise allow. This has likely contributed to rising rates of obesity and diet-related chronic diseases in the second half of the 20th century.

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