Monosodium Glutamate (MSG, E621)

What is MSG and what is it used for?

Glutamate is one of the amino acids that make up proteins, and our bodies also produce it themselves. MSG is the readily water-soluble sodium salt of this amino acid; today it is produced by fermenting raw materials such as starch or sugar beet.

Its job in food is flavour: it boosts umami, considered the fifth basic taste after salty, sweet, sour and bitter. This gives a full flavour to products that use less meat or stock. During digestion, the body does not distinguish between glutamate from MSG and glutamate from tomatoes or cheese.

Which products contain it?

• Instant soups, bouillon and stock cubes
• Crisps, snacks and flavoured crackers
• Ready-made seasoning and sauce mixes, soy sauce
• Instant noodles, frozen meals and processed meat products
• Restaurant and fast-food dishes

On the label it appears as “flavour enhancer (monosodium glutamate)” or “flavour enhancer (E621)”. Ingredients such as yeast extract and hydrolysed vegetable protein also naturally contain glutamate but do not carry a separate E number.

Is it harmful? The scientific assessment

MSG is one of the most studied food additives. In its 2017 re-evaluation, EFSA set a group acceptable daily intake (ADI) for glutamates and pointed out that some consumer groups may exceed this value at high intakes. In a normal diet, however, it is hard to come close to this limit.

The headaches, flushing and palpitations popularly known as “Chinese restaurant syndrome” have not been consistently reproduced in controlled studies in which people did not know what they were eating. Some people may report temporary, mild symptoms after taking large amounts of MSG on an empty stomach; however, this is not an allergy and there is no evidence that it causes lasting harm.

MSG contains sodium, but only about a third as much by weight as table salt. It is even thought that using it to replace part of the salt in food could reduce total sodium. The problem is that most products containing MSG are already high in salt.

Who should be careful?

• People on a salt-restricted diet: Those limiting sodium because of high blood pressure, heart or kidney disease should check the total sodium content of convenience products containing MSG.
• People who feel sensitive to it: If you think you have recurring complaints after MSG, cutting down on these products and discussing it with your doctor is a sensible approach.
• Young children: The real issue is not MSG but how often they eat salty snacks such as crisps and instant soup.

What to do when you see it on a label

E621 on its own does not make a product one to avoid. A more useful question is: how much salt does this product contain, and how often do I eat it? If you want to add umami flavour to dishes at home, you can use natural sources of glutamate such as tomatoes, mushrooms, aged cheese or bone broth.