E-numbers / Flavour enhancers / E621
also: sodium glutamate · monosodium L-glutamate
A flavour enhancer made by fermentation that gives food a savoury, umami taste. The same substance occurs naturally in tomatoes, cheese and mushrooms.
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Soybean Oil [45%], Chilli [25%], Onion [15%], Fermented Soybeans [ Soybeans, Water], Flavour Enhancer: [E621], Salt, Sugar, Sichuan Pepper Powder
European reviewers found that in the UK and EU, infants, toddlers and children can go over the daily limit.
739
of the 43,325 UK supermarket foods we checked declare E621 in their ingredients
That is 1.7%, counted by its code or its name.
Counted by NutraSafe from UK supermarket ingredient lists, September 2026. How we counted
Why it’s worth knowing. European reviewers found that in the UK and EU, infants, toddlers and children can go over the daily limit. Large single doses taken without food have brought on short-lived headaches in some people.
Monosodium glutamate (MSG) is the sodium salt of glutamic acid, an amino acid. It is made by fermenting starch, sugar beet, sugar cane or molasses with bacteria, then drying it into white crystals. The glutamate it adds is the same as the glutamate found naturally in many foods.
It adds umami, the savoury fifth taste. Glutamate switches on taste receptors on the tongue and deepens the meaty, brothy flavour of a dish, so makers can make food more savoury without adding more meat, salt or stock.
Crisps, stock cubes, instant noodles, gravy granules, ready meals, savoury snacks, soy and seasoning sauces, and takeaways. UK labels call it flavour enhancer (E621), monosodium glutamate or MSG.
In 2017 European reviewers set a shared daily limit for glutamic acid and glutamates of 30mg per kg of body weight, about 2g a day for an average adult, based on animal studies. They then found that real intakes can go over it, and at high intakes can reach doses linked to effects in people, for some groups, particularly infants, toddlers and children. This is about how much, not a claim that it is dangerous at normal use.
European reviewers set the daily limit at 30mg per kg of body weight, roughly 2g a day for an average adult, shared across E620 to E625. That is 100 times lower than the smallest dose that affected anything in the animal studies they reviewed.
Average intakes went over the limit in infants, toddlers, children and teenagers. Among the people with the highest intakes, every age group went over it.
Doses above the limit have been linked to effects in people: the cluster of MSG symptoms above 42.9mg per kg a day, headache at around 85.8mg per kg, a rise in blood pressure at 150mg per kg, and higher insulin above 143mg per kg. All sit above the daily limit and far above the amount in a single meal.
The idea that MSG causes headaches, flushing and a racing heart began with a letter in 1968 and became known as Chinese restaurant syndrome. When tested with neither the person nor the researcher knowing who had MSG, the reactions did not show up consistently, especially when MSG was eaten with food rather than as a big dose on an empty stomach. In people who believed they were sensitive, reactions were inconsistent, mild and not reliably set off.
Blinded studies with a dummy comparison did not consistently reproduce a pattern of symptoms at realistic amounts. Reactions in people who said they were sensitive were inconsistent and not serious.
A US review found short-lived, generally mild symptoms (headache, numbness, flushing, tingling, a racing heart, drowsiness) in some sensitive people only after 3g or more of MSG taken without food, far more than a normal meal provides.
Glutamate is one of the most common amino acids in the diet, and it occurs free in many everyday foods. The body handles glutamate from MSG and glutamate from those foods in the same way.
Free glutamate occurs naturally in tomatoes, Parmesan and other aged cheeses, mushrooms, peas, walnuts and meat. The body does not tell added and natural glutamate apart.
Daily limit. 30mg per kg of body weight a day, measured as glutamic acid, shared across the glutamates (European reviewers, 2017).
Parents keeping an eye on how many heavily seasoned processed snacks young children eat, and anyone who has noticed a reaction after large MSG-heavy meals, can limit it by checking for flavour enhancer (E621), monosodium glutamate or MSG on the label.
MSG carries one of the longest-running food scares. The Chinese restaurant syndrome story came from a single 1968 letter, and when researchers tested it blind, at amounts people actually eat, the symptoms did not reliably appear. The separate, evidenced point is how much people eat: the 2017 European review found intake can go over its proposed daily limit for infants and children, which is why it set a numerical limit and asked for lower permitted levels. The headline scare and the real regulatory point are two different things.
No. E621 is an approved flavour enhancer in Great Britain and the EU, and it is approved in the US too. The 2017 European review kept it allowed but set a daily limit and recommended lower maximum levels in food.
Blinded trials have not consistently linked normal amounts of MSG in food to headaches. European reviewers noted headache in studies at around 85.8mg per kg of body weight a day, and a US review found short-lived symptoms in some sensitive people only after 3g or more taken without food, far more than a typical meal.
Crisps, stock cubes, instant noodles, gravy granules, ready meals, savoury snacks, soy and seasoning sauces, and many takeaways. Glutamate also occurs naturally in tomatoes, aged cheese, mushrooms and meat, where it is not labelled as MSG.
Yes. It is made by fermenting plant sources such as starch, sugar beet, sugar cane or molasses with bacteria, with nothing from animals.
Last reviewed: 20 June 2026
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