All From a Bowl of Broth

MSG (monosodium glutamate) was discovered in 1908 by Kikunae Ikeda, a scientist who initially wanted to figure out what made his favorite soups, flavored with Laminaria japonica kelp and its stock, so delicious.

He noticed that kelp stock had a distinctly savory taste that couldn’t be categorized into any of the tastes he was familiar with: sweet, salty, bitter, and sour.

He called this new taste umami.

He was eventually able to isolate crystals of the compound responsible for this flavor: monosodium glutamate. His ultimate goal was to start a business to produce it and sell it, to help cooks improve their dishes with an easy-to-add source of umami flavor.

He figured out how to extract MSG from wheat and soybean at a larger scale, and started a food products company called Ajinomoto to sell it.¹ Ajinomoto is still around today.

In the 1950’s, MSG entered the American market. For a while, it was widely accepted as a food additive that helped enhance savory flavors.² It was accepted by the FDA in 1958 as “generally safe”, on the same level as basil, ginger, lavender, and other herbs.³

It was also well-used in Chinese restaurants to help bring a tasty, savory touch to their dishes and appeal to the average American diner. 

The Downfall of MSG and Rise of “Chinese Restaurant Syndrome”

In 1968, Dr. Robert Ho Man Kwok of the National Biomedical Research Foundation wrote to the New England Journal of Medicine reporting that he experienced some palpitations and numbness from eating food from Chinese restaurants.

From this correspondence, the term “Chinese Restaurant Syndrome” was established,⁴ and other news outlets like the New York Times reported on this.⁵

This term quickly caught on as more doctors reported similar symptoms, and MSG began to be linked to various adverse effects by scientific studies starting in 1969. Many diners who experienced discomfort after eating Chinese food began to blame it on MSG, the relatively new and unknown seasoning.

This was the beginning of a long era of misinformation around MSG, which still exists today.

For readers curious about the story of Dr. Robert Ho Man Kwok, there’s an entire saga about another man, Dr. Howard Steel, who came out in January 2018 saying he wrote the original letter and made up the names “Dr. Robert Ho Man Kwok” and “National Biomedical Research Foundation”. Apparently, that was debunked as a prank when Dr. Kwok was identified as a real person who apparently did write the letter.

If you’re curious to learn more about it, you can look into that on The Colgate Magazine’s article “The Strange Case of Dr. Ho Man Kwok”, and the transcript of This American Life Episode 668.

What is MSG?

If you don’t have a scientific background, “monosodium glutamate” might sound like a gnarly chemical and you might be convinced into thinking it’s not something you want in your food.

If you have a scientific education, you’d know it is way simpler than it sounds. 

First, let’s familiarize ourselves with glutamic acid.

If you remember your high school biology, you might recall glutamic acid – it’s one of the 20 amino acids, the building blocks of proteins. It’s categorized as “non-essential”, which means it’s not something that we have to eat to gain; our bodies can synthesize it.

No, it doesn’t mean it’s not essential (I know, terrible name)!

We definitely need it for our bodies to function. Glutamate, its anion form, is an important neurotransmitter, and also forms another neurotransmitter called GABA.⁶

Glutamic acid has 2 carboxyl groups.

In neutral solutions, it exists as an anion, which means it has a negative charge. In the case of glutamic acid, it is called glutamate, and has a charge of -1. This is because both of the carboxyl groups lose their hydrogens, become negatively charged, and the amine group takes on a hydrogen and becomes positively charged.

Depending on how acidic or basic the environment is, the molecule can take on different charges.

The “monosodium” portion of “monosodium glutamate” refers to the presence of 1 sodium (Na+) atom bonded to the glutamate. At physiological pH and in water, MSG dissolves and separates into the two components: Na⁺ and glutamate.

What Foods Contain Glutamate?

Glutamate is found in more foods than you’d think, including:

• Processed foods (meats, salty snacks, bouillon cubes, canned vegetables),⁷
• Vegetables and fruits (tomato, onion, green peas, cabbage, avocado)
• Meats and seafood (chicken, beef, pork, salmon, scallop, crab, shrimp)
• Cheeses (parmesan, emmenthaler, cheddar)⁸
• Many Asian condiments, like soy sauce

According to the FDA, the glutamate in our foods is indistinguishable from the glutamate in MSG, and our bodies metabolize (break down) the glutamates in the same way, mainly in the liver and small intestines.⁹

They report that the average adult consumes about 13g of glutamate from proteins in their food every day, and the glutamate from MSG is about 0.5g per day on top of that.¹⁰ 

Sure, glutamic acid (the amino acid, produced in our bodies) and MSG (monosodium glutamate) are different molecules when undissolved.

However, as soon as it hits any aqueous environment and our physiological pH, they dissolve, and are indistinguishable.

In addition, it’s impossible to be “allergic” to MSG, because as mentioned above, it dissolves as soon as we ingest it, and neither sodium nor glutamate trigger the immune response in a way that true allergens do.

As for the amazing umami taste that’s gained a ton of popularity as the cool, desired 5th taste in various cuisines, even burgers? It’s glutamate binding to a few types of umami receptors on our tongue.¹¹

Initial Studies

A few studies from around the 1960’s and 1970’s linked exposure to MSG to all sorts of adverse effects, such as stunted skeletal development, reproductive issues, brain damage, and obesity.^12,13

However, the general consensus is that those studies were not well-designed.⁷

The main issues with those studies were the techniques used to deliver MSG to the animals, and the doses they tested far exceeding what people are exposed to in food on a regular basis (about 0.5g per day).

One of the more well-known studies was by Olney, published in Nature in 1970, and used a dose of 0.5g/kg of body weight in the mice used.¹³

Let’s get that straight. 0.5g/kg is half a gram of MSG for every kilogram of body weight. That equates to 40g of MSG for an 80kg adult (the weight of an average adult in the U.S. between 2015-2018 was 77.5kg for women, and 90.6kg for men).¹⁴ 

That’s a lot of MSG!

In addition, this massive amount of MSG was injected into the brains of the infant mice tested, which does not replicate the way MSG is introduced to the average human consumer.

Correcting the Course

Decades of research has shown that MSG consumption is not linked to any adverse health outcomes related to “Chinese Restaurant Syndrome”.¹⁵ 

Well-Designed Studies Testing MSG and “Chinese Restaurant Syndrome”

The studies above were questioned as early as 1971.

A single and double blind study found no correlation with MSG and symptoms of “Chinese Restaurant Syndrome”.¹⁶

A randomized, double-blind, crossover study done in 1993 studied 71 people and if they experienced any symptoms previously associated with consumption of MSG. A crossover study exposes the participants to the placebo and the experimental treatment at different stages of the study, so each participant can act as their own control. MSG consumption did not elicit any adverse effects of symptoms more than the controls did.¹⁷ 

Another study from 2000, which was double-blind and placebo-controlled, found that there were no persistent or serious effects observed with MSG, and the frequency of any responses to MSG were very low, and mostly in people who knew they were ingesting MSG and already believe that they react adversely to it. When MSG was supplied in food, there were no responses and no differences compared to controls.¹⁸

MSG and the Brain

There’s no compelling evidence that MSG consumption adversely affects the brain and its functions.^19,20

Glutamate does not cross the blood-brain barrier to enter the brain; therefore, glutamate cannot go from the bloodstream to the brain.

As mentioned above, glutamate is a very commonly found neurotransmitter already in the brain, and if it’s in excess, it is able to enter the endothelial cells from the extracellular space in the brain, and then be dumped into the bloodstream as needed.

This is explained by the existence of transporters that have a very steep sodium ion gradient that makes it virtually impossible to move glutamate into the brain, even though it can be moved out of the brain.²⁰

MSG and Obesity/Weight

When it comes to obesity and other metabolic disorders, more research would be really interesting.

One study showed that consumption of MSG was linked to overweight development, and suggested that more research is necessary to establish a mechanism behind that link.²¹

Some studies show that MSG consumption is linked to anti-obesity effects, due to the MSG making food taste pleasant and reducing the amount of salt needed to season it.^22,23

However, other studies show no real links between MSG consumption and body weight.²⁴

Federation of American Societies for Experimental Biology (FASEB) has established that MSG is safe.

They observed short-term, mild symptoms such as flushing, tingling, numbness, and headaches in sensitive individuals who consumed 3 grams or more of pure MSG,²⁵ but that is a lot higher than the typical daily intake level (0.5g/day) of MSG recommended by the FDA.

In addition, comparing table salt (NaCl) and MSG, it’s been shown that if you have 100 grams of either compound, there’s 39.34 grams of sodium in table salt, and only 12.28 grams of sodium in MSG.

When you’re cooking and want to season 500 grams of a food item (such as rice, meat, or veggies), you can add 1/2 teaspoon of MSG instead of 1/2 teaspoon of salt, and that reduces the sodium content of what you used to season it by about 37%.²⁶

Pervasive Symptoms

The concept of “Chinese Restaurant Syndrome” stemming from exposure to MSG has fed into the general belief that Chinese food is unhealthy.

In 2019, health and lifestyle blogger Arielle Haspel opened Lucky Lee’s, a restaurant in New York City that advertised “clean” Chinese-American food that “will actually make [diners] feel good”.

She used advertising such as “We heard you’re obsessed with lo mein but rarely eat it. You said it makes you feel bloated and icky the next day? Well, wait until you slurp up our HIGH lo mein. Not too oily. Or salty.”²⁷ 

Her restaurant was shut down less than 1 year after opening, due to massive backlash related to racism and cultural appropriation. Not only was her restaurant a major example of cultural appropriation, but her marketing dripped with negative and racist stereotypes of Chinese food.

Even today, major corporations like Campbell’s Soup Company, Frito Lay, and General Mills advertise the lack of MSG in their products. In addition, you can find plenty of magazine articles listing top local restaurants and Yelp reviews raving about the lack of MSG at certain establishments, not to mention restaurant websites proclaiming they don’t use any MSG in their dishes.

The reality is, businesses of all sizes are finding it easier to appease a population’s misinformed biases, rather than try to educate them or be the change-maker.

It’s unfortunate that a 53-year-old trending topic, debunked by scientists over decades, is still affecting businesses today.

There’s no data out there that establishes “Chinese Restaurant Syndrome” as a real set of physiological symptoms by unbiased, double-blinded, controlled studies using foods that contain MSG.

Conclusion

Today, various scientific and health organizations such as the World Health Organization, FDA, and European Food Safety Association (EFSA) consider MSG to be generally recognized as safe (GRAS).⁷

It’s been well-established that it’s totally fine to consume MSG at reasonable levels.

We are not necessarily done studying MSG and the effects that it can have on our bodies. Science is always evolving, and that’s why it takes so much work: we have to keep up, and we’re always curious to learn more.

It’s important to continue to study MSG, or any other food additive or ingredient we’re interested in knowing more about, in an unbiased fashion through more well-designed, double-blind, placebo-controlled studies. 

In addition, it’s important to interpret these well-designed studies for what they are, without forcing illogical extrapolations.

Importantly, we report what’s known and not known all along the way.

In the meantime, if you’re feeling sick after eating Chinese food but you feel fine after eating Doritos, you can rest assured that the effects aren’t from MSG.