MSG and flavour enhancers: what the evidence actually shows

Few food ingredients have a reputation this far from the evidence. Monosodium glutamate has been tested for fifty years, cleared repeatedly, and a great many people still believe it makes them ill. The belief started with one letter in 1968.

The 1968 letter

In 1968 a doctor wrote to the New England Journal of Medicine describing numbness and palpitations after eating at Chinese restaurants. He speculated about several possible causes: the cooking wine, the sodium content, and MSG among them.

It was a letter to the editor, with no data behind it. The name "Chinese Restaurant Syndrome" stuck anyway. It survived for decades in medical textbooks and popular writing alike, and its racial framing helped keep it alive.

The many trials that followed found, consistently, that people who report reacting to MSG stop reacting when they cannot tell whether they have eaten it.

What MSG is

Glutamate is an amino acid, present in almost every protein food and manufactured continuously by your own body. MSG is its sodium salt.

It is made by fermenting starch or molasses with bacteria, in the same general way as vinegar or yoghurt. The product is chemically identical to the glutamate in parmesan, ripe tomatoes, soy sauce and human breast milk, which contains more free glutamate than most foods.

Your gut cannot tell them apart, and that is the problem for the sensitivity claim: a reaction to MSG that does not also happen with parmesan has no mechanism to work by.

The full list

Every flavour enhancer in our database, with its E number where it has one. Yeast extract and hydrolysed vegetable protein have none, which is part of why they are used.

Food	Notes
Glutamic acidE620	Glutamic acid (E620) is a flavour enhancer food additive.
Monopotassium glutamateE622	Monopotassium glutamate (E622) is a flavour enhancer food additive.
Disodium ribonucleotidesE635	Disodium ribonucleotides (E635) is a flavour enhancer food additive.
Disodium inosinateE631	Disodium inosinate (E631) is a flavour enhancer food additive.
Hydrolyzed vegetable protein	Hydrolyzed vegetable protein is a flavour enhancer food additive.
Disodium guanylateE627	Disodium guanylate (E627) is a flavour enhancer food additive.
Monosodium glutamateE621	Monosodium glutamate is a flavor enhancer. MSG adds umami taste to foods.
Yeast extract	Yeast extract is a savory flavoring paste. A concentrated umami ingredient made from yeast.

MSG rarely travels alone. Disodium guanylate, E627, and disodium inosinate, E631, are ribonucleotides that make the savoury effect far stronger in combination than any of them manage separately. Yeast extract and hydrolysed vegetable protein do the same job while allowing a label to avoid the three letters.

What the blinded trials found

For the symptom cluster in the original letter, headache, flushing, numbness and palpitations, the blinded evidence does not support MSG as the cause at dietary amounts. The largest multicentre double-blind placebo-controlled study found no consistent, reproducible response even among people who identified themselves as sensitive to it.¹

Two things sit alongside that without contradicting it. Very large doses taken on an empty stomach, well beyond what food delivers, have produced transient symptoms in some studies. And restaurant meals differ from home cooking in salt, fat, portion size, alcohol and histamine all at once, so feeling unwell after one is easy to explain without MSG.

If you are convinced MSG affects you, test it blind.

How to run a blind test

Have someone else cook the same dish twice on separate days, once with a teaspoon of MSG and once without, and not tell you which was which until afterwards. Write down how you felt each time. Three or four rounds gives you something worth reading. It takes more effort than cutting a food. Expectation has been shown to produce the symptoms on its own, so a test where you know what you ate cannot separate the two.

Journal your day in 30 seconds, find your triggers.

Where Triggerbites fits in

This list comes from the food data inside Triggerbites. The app grades every flavour enhancer by name and E number, yeast extract and hydrolysed protein included, and grades ordinary ingredients like parmesan and tomato for their natural glutamate.

Glutamate comes from many directions at once, added and natural, and almost nobody can reconstruct a week of it from memory. You journal your day in plain words or by voice, in about 30 seconds: "toast with Marmite and a coffee for breakfast, instant noodles and a Coke Zero for lunch, spaghetti with parmesan for dinner, headache by nine." The app finds the packaged products in a catalog of over a million and lists the flavour enhancers in each. Scanning the barcode or photographing the label works too.

During a blind test the diary holds the dates and how you felt on each one, ready to match against the list your cook kept. Over a few weeks of ordinary logging the app ranks what your symptoms keep following, including reactions that show up days later, which tells you whether glutamate is on that list at all.

High-glutamate foods covers the natural side of the same question.

Log your day in 30 seconds

Text, voice or photo. Log as you go, or recap it all in the evening.

Your food, broken down

Meals become ingredients and sensitivity profiles: histamine, salicylates, FODMAPs, allergens, and even the additives on packaged food.

Everything in the same journal

Symptoms, supplements, sleep, stress, exercise and mood, beside what you ate.

See what repeats over time

Patterns between what you eat and how you feel, including delayed reactions that show up days later.

Triggerbites Features

• Log your day in 30 seconds: Text, voice or photo. Log as you go, or recap it all in the evening.
• Your food, broken down: Meals become ingredients and sensitivity profiles: histamine, salicylates, FODMAPs, allergens, and even the additives on packaged food.
• Everything in the same journal: Symptoms, supplements, sleep, stress, exercise and mood, beside what you ate.
• See what repeats over time: Patterns between what you eat and how you feel, including delayed reactions that show up days later.

Common questions

What is MSG made of?

Monosodium glutamate is the sodium salt of glutamic acid, an amino acid found in almost all protein. It is produced by fermenting starch or molasses with bacteria, much like vinegar or yoghurt.

Is MSG the same as the glutamate in parmesan?

Chemically yes. Once either reaches your gut it is the same molecule, and your body has no way to tell which one it came from. A ripe tomato, aged parmesan and a spoon of MSG deliver the same amino acid.

Does MSG cause headaches?

Blinded trials have not found a reliable link. The effect tends to disappear once people no longer know whether they are eating it. Reviews of the evidence have consistently concluded that MSG does not cause the symptom cluster attributed to it at normal dietary amounts.

Where did Chinese Restaurant Syndrome come from?

A letter to the New England Journal of Medicine in 1968, in which a doctor described symptoms after eating at Chinese restaurants and speculated about several causes including MSG. It was an anecdote with no data behind it, and the name stuck for decades.

What are disodium inosinate and guanylate?

Ribonucleotides. Disodium guanylate is E627 and disodium inosinate is E631, used alongside MSG because the combination is far more savoury than either alone. They are usually derived from yeast or fish. If a label lists MSG, one of these is often beside it.

How do I test whether MSG affects me?

Properly, which means blinded. Have someone else prepare two versions of the same dish, one with added MSG and one without, on separate days, without telling you which. Expectation does most of the work in this area, so an unblinded test tells you very little.

Live, love, log. 🧡