Is MSG bad for you? What double-blind trials actually found
When people did not know if they got MSG or a placebo, reactions were few, did not repeat, and vanished with food. What JECFA, FASEB and FSANZ found, and sodium vs salt.
- The largest double-blind trial, 130 people, found 5 g of MSG on an empty stomach caused slightly more symptoms than placebo, but they did not repeat and did not appear when MSG was taken with food.
- JECFA set no limit ("ADI not specified"). FASEB in 1995 found brief symptoms in some people given 3 g or more without food.
- MSG is about 12% sodium by weight; table salt is about 39%. Fish sauce itself is high in free glutamate.
- If you think you react to MSG, see a doctor. The cause may be something else in the meal.
MSG is monosodium glutamate, the sodium salt of glutamic acid, an amino acid already present in almost every food. The best-designed trials, where neither participants nor researchers knew whether each dose was MSG or a placebo, found that a large dose on an empty stomach can give some people brief symptoms, but the symptoms did not repeat and did not appear when MSG was eaten with food. The major food safety bodies do not consider MSG a hazard for the general population.
This article does not push anyone to add more MSG, and it does not tell anyone whether they personally react. It sums up what the studies found, the actual numbers, and how to use that when ordering.
What MSG is and where glutamate comes from
Glutamate is one of the most abundant amino acids in nature, making up 10-40% of the weight of most proteins. In its free form, not bound into protein, it gives the savoury taste called umami. MSG is made by fermentation from sugar cane or beet molasses or from starch.
A 2003 report by FSANZ (Food Standards Australia New Zealand) collected free glutamate figures for foods. A few close to Thai cooking:
| Food | Free glutamate (mg per 100 g) |
|---|---|
| Fish sauce (nam pla) | 950 |
| Oyster sauce | 900 |
| Soy sauce (China) | 926 |
| Parmesan cheese | 1,200 |
| Tomatoes | 140 |
| Corn | 130 |
Glutamate from fish sauce, from tomatoes or from MSG is the same compound to the body.
It started with “Chinese restaurant syndrome”
In 1968 a letter in the New England Journal of Medicine described symptoms after eating at Chinese restaurants, and MSG was suggested as the cause. Many reports followed, but most were anecdotes from people who knew what they had eaten. Someone who believes they react to MSG is likely to notice symptoms. The fix for that is a double-blind, placebo-controlled trial.
The 130-person trial
A multicentre study led by Geha, published in 2000, enrolled 130 people who said they reacted to MSG. They were given 5 g of MSG or a placebo in a 200 ml citrus drink, without food, and did not know which they got on which day.
Walk through the results step by step:
- In the first round of 130 people, 50 (38.5%) reacted to MSG only, 17 (13.1%) to placebo only, and 19 (14.6%) to both.
- Of the 37 who reacted to 5 g of MSG but not to placebo, only 19, about half, reacted the same way when retested.
- In a further round, 2 people reacted to MSG and not placebo both times, but their symptoms differed from round to round.
- Those two were then tested with food: three MSG challenges and three placebo. Each reacted to only 1 of the 3 MSG challenges, and not with the same symptoms as before.
The authors concluded that large doses of MSG without food may cause more symptoms than a placebo in people who believe they react, but the responses were infrequent, inconsistent, not reproducible, and not seen when MSG was given with food.
Of 130 people sure they reacted to MSG, none produced the same reaction consistently across repeated blinded tests.
What the main bodies concluded
| Body | Conclusion |
|---|---|
| JECFA (FAO/WHO Expert Committee on Food Additives), 1987 evaluation | No numerical limit needed: “ADI not specified”. Blinded trials did not show a clear link. |
| FASEB (for the US FDA), 1995 | A small group may get brief symptoms within 1 hour after 3 g or more without food. A small group with severe asthma might react to 1.5-2.5 g. |
| FSANZ, 2003 | No convincing evidence of serious illness. Lab-provoked symptoms were inconsistent and mild, and likely reduced when eaten with food. |
| US FDA | Classed as GRAS (generally recognised as safe); must be named on the label. |
The first two differ slightly. JECFA found the trials did not show a clear relationship; FASEB accepted that a small group may react to a large dose on an empty stomach. FSANZ, reviewing later, agreed with FASEB on the 3 g-without-food point.
Putting the numbers next to a real plate
Example 1: how much is 3 g?
- The US FDA says a typical serving of food with added MSG contains less than 0.5 g.
- UK data put average intake at 590 mg a day, with the highest consumers around 2,330 mg.
- A highly seasoned restaurant meal might reach 5,000 mg or more.
Getting 3 g in one go with no other food is hard, because MSG always comes with food.
Example 2: sodium in MSG versus salt
- The FSANZ report gives MSG a molecular weight of 187.13, with one sodium atom weighing 22.99.
- 22.99 ÷ 187.13 ≈ 0.123, so 1 g of MSG contains about 123 mg of sodium.
- Table salt (NaCl): 22.99 ÷ 58.44 ≈ 0.393, so 1 g of salt contains about 393 mg of sodium.
Gram for gram, MSG has roughly a third of the sodium of salt, but it still counts. If you are cutting salt, most of the sodium in a Thai dish usually comes from fish sauce, soy sauce and broth. See Ordering Thai food with less salt and sugar for what to ask.
Common mistakes
- Thinking “no MSG” means no glutamate. 100 g of fish sauce carries 950 mg of free glutamate.
- Blaming MSG for every after-meal headache. The FSANZ report notes most people who suspect MSG do not react in blinded tests. Something else in the food may be the cause.
- Citing unblinded studies. If people know they got MSG, the results lean towards what they already believe.
- Deciding it is safe, so more is fine. MSG still contains sodium, and too much flattens the taste of a dish.
- Self-diagnosing. If symptoms keep coming back after meals, see a doctor to find the actual cause instead of cutting foods one after another.
Summary
Double-blind trials found that a large dose of MSG on an empty stomach may give some people brief symptoms, but they are inconsistent, not reproducible, and not seen when MSG is eaten with food. That is why the major bodies do not regard it as a hazard for the general population. If you prefer milder food, order without MSG; just know the plate still has glutamate from fish sauce and sauces. If you suspect a reaction to anything, see a doctor.
Sources
FAQ
If I order "mai sai phong chu rot" (no MSG), will the dish have no glutamate?
No. Fish sauce, soy sauce, oyster sauce, tomatoes and meat all contain glutamate naturally, and the body treats glutamate from MSG and from fish sauce as the same thing. If you prefer a milder taste, ask for no MSG, but the dish will still contain glutamate.
I get a headache after MSG. Does that mean I am sensitive?
Not necessarily. In trials where participants did not know what they were given, most people who believed they reacted did not react consistently on repeat tests. The cause may be another part of the meal. If it happens often, see a doctor to find the real cause.
Should people with asthma avoid MSG?
FASEB (1995) found a small group with severe, poorly controlled asthma might react to 1.5-2.5 g taken without food. The 2003 FSANZ report concluded that newer studies do not show MSG to be a significant trigger. If you have asthma, ask the doctor who treats you.
Ingredients and heat vary by kitchen and recipe. If you have a food allergy, ask before you order, every time.