MSG: The Science Behind the Most Misunderstood Seasoning

In 1968, a physician named Robert Ho Man Kwok wrote a letter to the New England Journal of Medicine. He described feeling numbness, weakness, and heart palpitations after eating at Chinese restaurants. He speculated several possible causes, including MSG.

That letter (a single physician’s personal speculation, not a study) launched one of the most persistent food myths of the 20th century.

MSG became vilified. “No MSG” became a marketing claim. Chinese restaurants were blamed for causing illness. And the scientific evidence? That came later, and it told a very different story.

What Is MSG?

MSG stands for monosodium glutamate. It’s the sodium salt of glutamic acid, one of the most common amino acids in nature.

When you eat MSG, it dissolves into two components: sodium ions and glutamate ions. The sodium contributes slightly to saltiness. The glutamate does something more interesting: it activates taste receptors specifically tuned for umami, the fifth basic taste.

MSG was first isolated in 1908 by Japanese chemist Kikunae Ikeda, who was trying to understand why certain foods (particularly kombu seaweed) had such an intensely savory flavor. He identified glutamate as the compound responsible, extracted it, and found a way to produce it commercially.

Today, MSG is made through bacterial fermentation of carbohydrates, the same basic process used to make yogurt, vinegar, and amino acid supplements.

The Umami Connection

Umami is often described as savory, meaty, brothy, or mouthwatering. It’s a distinct taste quality separate from sweet, salty, bitter, and sour.

Your tongue has specific taste receptors for glutamate: mGluR1 and T1R1/T1R3 receptor complexes. When glutamate activates these receptors, it signals “protein is present” to your brain. This makes evolutionary sense. Glutamate is abundant in protein-rich foods, so tasting it reliably indicates a nutritionally valuable food source.

Glutamate is found naturally in extremely high concentrations in:

• Parmesan cheese: ~1,200 mg glutamate per 100g
• Soy sauce: ~1,090 mg per 100g
• Anchovies: ~630 mg per 100g
• Tomatoes: ~140 mg per 100g (higher in dried/concentrated form)
• Mushrooms: ~70–180 mg per 100g

When you add MSG to food, you’re adding the same molecule that makes these foods taste great. Your digestive system handles it identically.

The Chinese Restaurant Syndrome Myth

The reaction Kwok described became known as “Chinese Restaurant Syndrome.” It entered medical vocabulary and popular consciousness without being rigorously tested.

When researchers finally ran controlled studies, where participants received either MSG or an identical-tasting placebo without knowing which, the results were consistent and clear: MSG did not reliably produce symptoms.

A landmark 1993 study published in the Journal of Allergy and Clinical Immunology gave self-identified MSG-sensitive subjects either MSG or placebo under double-blind conditions. They couldn’t reliably tell which was which, and reactions occurred in both groups at similar rates.

Multiple subsequent studies confirmed this. A 2000 review in Food and Chemical Toxicology concluded: “There is no consistent evidence in the published literature to support the claim that MSG causes illness in human beings.”

The FDA conducted its own review and found no evidence of serious harm from MSG at normal consumption levels. It maintains MSG’s GRAS (Generally Recognized as Safe) status.

Why Did People Believe They Were Reacting?

If controlled studies show MSG isn’t causing reactions, why do so many people report getting sick from it?

Several mechanisms are likely at work:

The nocebo effect. If you believe a substance will make you sick, your body can produce real physical symptoms. This is the negative version of the placebo effect, and it’s well-documented. Once “Chinese Restaurant Syndrome” became widely known, people eating Chinese food expected to react, and many did.

Other ingredients. Chinese restaurant food often contains high sodium, large portions, alcohol (in cooking wine), high fat, and spicy ingredients. Any of these could cause the symptoms people described, such as headache, flushing, and sweating. MSG rarely gets the chance to be ruled out when so many other potential culprits are present.

Genuine food sensitivities. Some people are sensitive to high-histamine foods, specific spices, or sulfites. These sensitivities are real, but they’re not caused by glutamate.

Confirmation bias. People who believe they’re MSG-sensitive notice symptoms after Chinese food and attribute them to MSG. They don’t notice that they also get headaches after eating parmesan or drinking red wine, both of which contain comparable or higher glutamate levels.

How Much Glutamate Are You Already Eating?

This comparison is worth sitting with: the average person in a Western diet consumes roughly 13 grams of bound glutamate per day from proteins naturally present in food. On top of that, they consume about 1 gram of free glutamate from vegetables, cheeses, fermented foods, and condiments.

A typical serving of MSG-seasoned food might add 0.5–1 gram of glutamate. That’s a small addition to a baseline that’s already substantial.

Your gut treats all dietary glutamate the same way. About 95% of it is metabolized in the intestinal wall before it even reaches the bloodstream. The small amount that enters circulation is handled by the liver. Glutamate doesn’t readily cross the blood-brain barrier under normal conditions.

MSG and Sodium Intake

One legitimate reason to think about MSG: it contains sodium. MSG is about 12% sodium by weight, compared to table salt at 39% sodium.

This actually means MSG can reduce total sodium intake. Using MSG in place of some salt achieves equivalent perceived saltiness with less sodium overall, because glutamate enhances saltiness perception. Studies on MSG as a sodium-reduction strategy are generally favorable. You can cut sodium by 25–40% in some dishes by substituting MSG without a perceived flavor loss (Yamaguchi & Ninomiya, 2000, Journal of Nutrition).

For people managing sodium intake for blood pressure reasons, MSG isn’t a danger. It might actually help.

The Bottom Line

MSG has been consumed by hundreds of millions of people for over a century, studied intensively for decades, and consistently found safe. The fears around it trace to a single anecdotal letter and a cultural bias that associated Chinese food with illness.

Parmesan cheese has higher glutamate concentrations than MSG-seasoned dishes. Soy sauce contains comparable amounts. Nobody suggests avoiding those foods.

Use MSG if you want to. Avoid it if you prefer. But avoid it because of personal preference, not because of safety concerns that don’t hold up to scientific scrutiny.