Monosodium glutamate, or MSG, is a household name. And manufacturers have been adding it to foods for many decades.
Even if you don’t know too much about the compound, you’re probably aware that it’s got a bad reputation. But is this justified?
The story of MSG isn’t just a journey through health and nutrition research.
It’s also an odd tale involving misinformation, scaremongering, and the power of mainstream media to blow things out of proportion.
But before we get tangled up in the details, let’s cover the basics.
What is MSG?
MSG is a flavor enhancer. It beefs up a food’s savory, or umami, taste.
In a nutshell, it’s an amino acid called glutamate combined with regular salt to keep it stable.
Manufacturers add it to a wide range of foods, including canned vegetables, soups, deli meats, restaurant foods, and savory snacks.
MSG also occurs naturally in some foods, like cheese, walnuts, mushrooms, seaweed, peas, broccoli, tomatoes, soy sauce, and breast milk.
Although it’s widespread in manufactured products, you won’t always spot it on food labels. Because it has a bit of a bad reputation — which isn’t necessarily warranted, as we’ll see later — food manufacturers tend to hide it.
Here are some of the other names for MSG that you might find on food labels:
monosodium glutamate monohydrate
monosodium L-glutamate monohydrate
sodium glutamate monohydrate
flavor enhancer E621
How does MSG work?
MSG activates glutamate receptors in your mouth. These receptors send signals to your brain, informing it that you’ve eaten something incredibly savory.
When MSG is broken down in your gut, the amino acid glutamate can provide energy for your gut or help build other important compounds.
Interestingly, glutamate is a neurotransmitter — a compound that your brain and nerves use to communicate.
Although dietary glutamate probably doesn’t make it to your brain, it seems likely that glutamate might be used within your gut’s extensive system of nerves.
We should note that glutamate, not MSG, occurs in all foods that contain protein — so that’s dairy, eggs, meats, nuts, and so on.
MSG and health
According to the United States Food and Drug Administration (FDA), MSG is “generally recognized as safe.”
Similarly, the European Food Information Council says:
“MSG is one of the most extensively studied food ingredients in our food supply. Hundreds of studies and numerous scientific evaluations have concluded that MSG provides a safe and useful taste enhancer for foods.”
Over the years, though, it’s been blamed for headaches, migraine episodes, blindness, convulsions, behavioral problems in children, and more.
But there’s no strong scientific evidence that MSG impacts health.
So, why is MSG associated with negative health outcomes? To answer this and other questions, we’ll go on a short tour through history. Are you sitting comfortably?
A short history of MSG
MSG was first invented in Japan in 1908 by a chemist called Ikeda Kikunae. He hoped that this cheap, easy-to-manufacture condiment might encourage people to eat more bland but nutritious foods.
Eventually, this powdered taste explosion, marketed as Ajinomoto, made it into kitchens and dining tables across Japan. And by 1931, Kikunae’s company was making 1,077 tonnes per year.
In the 1930s, Ajinomoto thoroughly infiltrated Taiwan before making its way to China and other cities in Asia with large Chinese populations.
By the 1930s and 1940s, the U.S. was the largest importer of MSG from Japan. American companies that manufactured canned foods saw the benefits of this cost-effective way to take the blandness out of their products.
However, the tide began to turn in the 1960s. People started losing faith in additives.
In 1968, scientists claimed that saccharin caused cancer. Soon after, the FDA banned a sweetener called cyclamate due to safety concerns. People’s trust in the food industry was shaken.
Then, a seemingly innocuous letter in the hallowed pages of a respected medical journal ruined MSG’s image for good.
‘Chinese restaurant syndrome’
In 1968, a letter written by Dr. Robert Ho Man Kwok from the National Biomedical Research Foundation, in Silver Spring, MD, appeared in The New England Journal of Medicine. It was titled “Chinese-restaurant syndrome.”
In it, Dr. Kwok writes, “For several years since I have been in this country, I have experienced a strange syndrome whenever I have eaten out in a Chinese restaurant.”
He complained of symptoms including numbness, weakness, and an increased heart rate.
Following the publication, the journal received a flurry of letters. Some agreed with Dr. Kwok, others mocked the idea, and others contained fanciful case studies intended to amuse.
Once the mainstream media caught wind of this innocuous scientific chatter, they exploded with related stories from readers and, of course, an unhealthy dose of scaremongering.
With the cyclamate debacle under his watch, then-President Richard Nixon wanted to play it safe. He ordered a thorough examination of current food additives, just to make sure.
Below, we’ll look at some of the more recent research into MSG and health but, suffice it to say, MSG wasn’t banned.
Its online dictionary now explains that there's no scientific evidence to support the term, and that it’s “misleading and potentially offensive.”
An unexpected twist
The tale of a short letter causing a widespread, decades-long panic about a single ingredient is weird enough. But it gets stranger.
In 2017, Prof. Jennifer LeMesurier wrote a paper about how the flames of fear surrounding MSG were fanned by racism.
Following its publication, Prof. LeMeurier received a phone call from a Dr. Howard Steel. And here’s your twist: Dr. Steel told the academic that he had written the fateful letter to The New England Journal of Medicine as part of a bet.
He explained that a colleague had bet him $10 that he couldn’t get published in a medical journal. After a Chinese meal and many beers, he had his lightbulb moment.
Dr. Steel told Prof. LeMesurier how he’d made up the name Dr. Robert Ho Man Kwok and created the fictional institution where he supposedly worked — the National Biomedical Research Foundation, in Silver Spring, MD.
He won the bet but sparked a decades-long health panic … or did he?
What? Another twist?
Researchers at This American Life picked up on the tale of the spoof letter and, in 2019, investigated further.
They found that, unexpectedly, there really had been someone called Dr. Robert Ho Man Kwok — a pediatrician at the very real National Biomedical Research Foundation, in Silver Spring, MD.
By this time, both Dr. Steel and Dr. Kwok had died, so the journalists contacted the real Dr. Kwok’s family. The family members explained that Dr. Kwok had written that fateful letter, and he’d been pleased that it had reached print.
Confused, the team also contacted Dr. Steel’s daughter. She had grown up hearing her father tell this story, so she was initially surprised by the news.
However, as she went on to explain, her father loved a hoax, and you could never really know whether he was telling the truth. She also told the journalists that the buddy had never paid the $10. Perhaps they had both been in on the ruse.
This, it seems, had been the swan song of an aging prankster.
So, tall tales aside, let’s get back to the science, shall we?
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Does MSG cause brain damage?
This rumor started after researchers in 1969 found that if you injected MSG into baby mice, they developed brain damage.
These poor rodents also had obesity, problems with their bones, and a range of other issues.
However, there’s a vast difference between consuming MSG and injecting it. And there’s also a substantial difference between a baby mouse and you.
There’s no evidence from human studies that MSG impacts your brain.
MSG and headaches
One of the most common concerns about MSG is that it might cause headaches. However, to date, little research has investigated whether this effect is real.
A review from 2016 concluded that much of the research wasn’t of good enough quality to make solid conclusions. And those studies that did find an effect tended to use high doses.
What about obesity?
Some people believe that consuming MSG might increase the risk of obesity.
One theory is that if food tastes better, you’re more likely to overeat.
Another is that your body becomes less sensitive to a hormone called leptin, which helps regulate your fat metabolism and weight management. This is an area that scientists are still looking into.
A study from 1987 involving 32 people with asthma concluded that MSG could “provoke asthma.”
Still, the authors of the review explain that the current evidence is limited, especially in children, so it might be worth carrying out more studies.
It may be that some people are more sensitive to MSG than others. A person might sweat or develop a headache in response to the additive, for instance.
Nowadays, this is called “MSG symptom complex.” But there’s still not much evidence that it’s a real concern.
There’s been little research in recent years, but a telling study from more than 20 years ago recruited 130 people who believed they were sensitive to MSG.
In a number of trials, each participant received both MSG and a placebo, either alone in a capsule or in food.
The scientists concluded that these participants with “sensitivities” were more likely to have a response when they had consumed a large dose of MSG alone, rather than in food.
The team adds that any effects weren’t serious and didn’t last. They also explain that even the people who did respond to MSG in some of the trials didn’t respond in all of them.
Either way, if you find yourself experiencing unwanted effects from foods containing MSG, it might be best to avoid them or limit how much you have.
What’s the verdict?
The story of MSG shows how something relatively benign can be dramatically vilified by a very minor event: A single letter in a printed medical journal sparked a rumor that persists to this day.
It also underlines how difficult it is to know what to believe when it comes to nutrition.
That’s why, at ZOE, we focus on keeping it simple: No food is off the table, and nothing is untouchable. Simply focus on eating as many fresh, plant-based foods as possible, and let your body do the rest.
Concentrating on single ingredients is a road to confusion; instead, focus on real foods.
It’s true that some foods that contain MSG aren’t great for you, like ultra-processed and fast foods, for instance. So, limiting your intake of those might be a good idea, whether you trust MSG or not.
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