What is E621? Monosodium Glutamate Explained

The discovery of umami

MSG's story starts in 1908 with Kikunae Ikeda, a chemistry professor at Tokyo Imperial University. Ikeda noticed that dashi broth made with kombu seaweed had a savoury depth that didn't fit any of the four recognised tastes of the time — sweet, sour, salty, bitter. Investigating the broth, he isolated glutamic acid as the compound responsible and named the taste umami, from the Japanese umai (delicious). He then found that the sodium salt of glutamic acid — monosodium glutamate — carried the same taste in a stable, water-soluble crystalline form, and patented the production process the same year. Ikeda co-founded Ajinomoto to manufacture it commercially; the company is still the world's largest MSG producer today. Umami wasn't formally accepted by Western food science as a fifth basic taste until the 1980s and 90s, when researchers identified the specific glutamate receptors (T1R1/T1R3) on the tongue that Ikeda's chemistry had predicted eight decades earlier.

How MSG actually works on your tongue

MSG is the sodium salt of glutamic acid, a naturally occurring amino acid. Once dissolved — in saliva, in a broth, in any watery food — it separates into a sodium ion and a free glutamate ion. The free glutamate ion is the active part: it binds to umami receptors on the tongue in the same way sugar binds to sweet receptors, producing a savoury, mouth-filling taste that intensifies and rounds out other flavours rather than adding a taste of its own. This is why MSG is used as a flavour enhancer rather than a primary seasoning — it doesn't taste of much on its own, but it makes stocks, sauces and processed foods taste more ‘full’ and less flat.

The Chinese Restaurant Syndrome myth

MSG's reputation problem traces back to a single 1968 letter published in the New England Journal of Medicine, in which a physician described symptoms — numbness, weakness, palpitations — he'd experienced after eating at Chinese restaurants, speculating MSG might be the cause. The letter coined the term ‘Chinese Restaurant Syndrome’, and the idea spread through media coverage far faster than any actual research could test it. Decades of controlled trials followed. In properly designed double-blind, placebo-controlled studies — where neither the participant nor the researcher knows who received MSG and who received a placebo — researchers have not found a consistent, reproducible link between MSG at normal dietary doses and the symptoms originally described. The US FDA classifies MSG as Generally Recognized As Safe (GRAS), the same category as ordinary table salt and baking powder. Food historians and public health researchers have also increasingly pointed out that the panic specifically targeted Chinese cuisine while ignoring that MSG's flavour molecule, glutamate, is naturally abundant in many Western staples — parmesan cheese, tomatoes, mushrooms — eaten without concern. A small number of people do report subjective sensitivity to large single doses of MSG taken without food, but this hasn't been reliably reproduced under blind test conditions in the way food-safety science requires to establish a genuine causal effect.

What EFSA's 2017 review actually found

In 2017, the European Food Safety Authority completed a comprehensive re-evaluation of glutamates (E620–E625) as a group — the first time this had been done since their original 1970s-era approval. Unlike many additive reviews, this one changed the rules: EFSA set a group Acceptable Daily Intake (ADI) of 30mg per kg of body weight per day, where previously glutamates were classed as ‘acceptable, not specified’ (effectively unlimited). This wasn't a safety scare — it was EFSA applying modern risk-assessment standards to older approvals, based on animal studies showing effects only at very high doses, well above what's realistic through diet. For a 70kg adult, the new ADI works out to around 2,100mg of glutamate a day — several times what a typical diet delivers even with regular use of MSG-seasoned food. The takeaway from EFSA's own findings is reassurance with a boundary attached, not a reason to avoid E621 at normal cooking and eating levels.

MSG isn't the only source of glutamate in your diet

One of the more overlooked facts about MSG is that the compound responsible for its taste — free glutamate — occurs naturally in many everyday foods, often at higher concentrations than a typical seasoned dish would contain from added E621. Parmesan cheese carries roughly 1,200mg of free glutamate per 100g; ripe tomatoes around 140mg per 100g; mushrooms, seaweed (including the kombu Ikeda started with), soy sauce and fish sauce are all naturally glutamate-rich. This is why slow-cooked stocks, aged cheeses, and fermented sauces all carry that same savoury depth MSG is added to replicate — the body doesn't distinguish between glutamate from a parmesan rind and glutamate from a sachet of seasoning; the ion is chemically identical either way.

The ‘no MSG added’ label nuance

Products labelled ‘No MSG Added’ can still contain meaningful amounts of free glutamate from other ingredients — hydrolysed vegetable protein, yeast extract, and autolysed yeast all naturally release free glutamate during processing, producing a very similar umami effect without containing MSG in the specific E621 sense. This isn't a loophole exactly — the label is accurate, MSG genuinely wasn't added — but it means ‘MSG-free’ marketing doesn't necessarily mean glutamate-free, which is worth knowing if you're specifically trying to reduce dietary glutamate rather than just avoiding the E621 additive by name.

Where E621 actually turns up

Beyond the obvious — Chinese and other East and Southeast Asian cuisines, where it's a standard pantry seasoning — E621 is widely used in instant noodles and ramen seasoning sachets, potato crisps and savoury snacks, stock cubes and bouillon powder, canned and packet soups, processed and cured meats, ready meals, and savoury seasoning blends. It's popular with manufacturers because a small amount goes a long way: MSG lets a product taste fuller and more savoury while using less actual meat, cheese or stock extract, which is partly a cost-saving measure and partly why heavily processed convenience foods lean on it more than fresh or minimally processed alternatives.

How common is E621, really?

Open Food Facts — the same public database this site's additive information is built on — lists hundreds of specific products carrying E621 in individual categories alone: 953 in sausages and cured meats, 310 with a vegan label, and hundreds more across instant noodles, crisps and ready meals. That's a useful sanity check on how routine E621 actually is in the food supply, rather than the exotic or rare ingredient its reputation sometimes suggests — it's one of the most common flavour enhancers in ordinary packaged food, alongside the other glutamates and ribonucleotides covered below.

Other umami flavour enhancers, if you're comparing

E621 isn't the only additive used to boost umami, and it's often used alongside the others rather than instead of them. E627 (disodium guanylate) and E631 (disodium inosinate) are nucleotide-based enhancers, frequently blended with MSG for a stronger combined effect than either delivers alone — E635 is literally that blend in a single additive. E622 (monopotassium glutamate) is a non-sodium alternative to E621, sometimes used where a lower-sodium label claim matters. If you're checking a label with any of these names on it, you're looking at the same broad umami-enhancer family E621 belongs to.

Who should actually be cautious with E621

Almost everyone can eat MSG without any issue, but two groups genuinely warrant a closer look. People with severe, medically diagnosed sulphite or histamine sensitivities sometimes report cross-reactivity with glutamate-rich foods generally, though this is about the broader food category rather than MSG specifically. And anyone managing overall sodium intake for a medical reason (hypertension, kidney or heart conditions under medical supervision) should note that MSG itself is roughly one-third the sodium of table salt by weight for the same seasoning effect — often a net reduction if it replaces added salt, but worth mentioning to a GP or dietitian managing a strict sodium target rather than assuming it's automatically fine. Outside of these two specific cases, there's no general population group current guidance asks to avoid E621.

Is MSG safe during pregnancy?

Yes — there's no pregnancy-specific restriction on MSG in EU, UK or US food safety guidance. EFSA's Acceptable Daily Intake for glutamates applies across the general population, pregnant women included, and neither the NHS nor the FSA lists MSG among the ingredients to avoid or limit during pregnancy — a list that does include things like unpasteurised soft cheese, raw shellfish and high-mercury fish. The lingering worry many people have about MSG in pregnancy traces back to the same debunked ‘Chinese Restaurant Syndrome’ myth covered above, rather than to any pregnancy-specific evidence. If you're pregnant and cutting back on processed or heavily seasoned food for other reasons — salt intake, calorie tracking, general dietary caution — that's a reasonable personal choice, but it isn't something current food safety guidance asks specifically of MSG.

Common myths about E621, checked against the evidence

Further reading

• EFSA's 2017 re-evaluation (the source of the ADI figure)
• FDA: Questions and Answers on Monosodium Glutamate (MSG)