Glutamate (MSG)

Glutamate and monosodium glutamate: what are we talking about?

Theglutamate(or glutamic acid) is an amino acid, one of the building blocks of proteins. Our bodies make it themselves, and it is found in many foods. It is what gives rise to the savoury taste ofumami, often described as a rich, savoury taste, close to broth.

Themonosodium glutamate(MSG in English) is the sodium salt of this acid. Today it is produced by fermenting sugary or starchy plant materials (starch, beet, sugar cane, molasses), then added to foods to enhance flavour. In the European Union, it is one of the additives classed asflavour enhancers.

The family of glutamate additives covers the numbersE620 to E625: glutamic acid (E620), sodium glutamate (E621), potassium glutamate (E622), calcium glutamate (E623), ammonium glutamate (E624) and magnesium glutamate (E625). For general context on additives, see our articleAdditives: are they all a real danger?.

A taste already present in many foods

Glutamate is not a foreign body in our diet. It occurs in free form in common foods:

• thetomatoes, especially ripe ones;
• certaincheeses, especially matured ones;
• thesoy sauceand soy extracts;
• thebreast milk, where glutamate and glutamine together make up nearly 70% of free amino acids, according to a review published in Frontiers in Immunology.

The US FDA estimates that an adult consumes on average around 13 grams of glutamate a day through the proteins in their diet, compared with about 0.55 gram a day from added monosodium glutamate. The body makes no chemical distinction between the glutamate in a cheese and that in an additive: it is the same ion. What changes is the context: in a raw food it comes with the rest of the food matrix, in an industrial product it is there to boost a taste.

The "Chinese restaurant syndrome": origin of a reputation

It all started with a short letter published in April 1968 in the New England Journal of Medicine. An American doctor, Robert Ho Man Kwok, described numbness, palpitations and weakness felt after meals in Chinese restaurants. He suggested three possible causes: salt, cooking wine, or perhaps monosodium glutamate. The journal named the phenomenon "Chinese restaurant syndrome", and other doctors reported similar experiences in the following weeks.

Glutamate then became the prime suspect, even though the letter proved nothing: it was just one hypothesis among others. The term, now considered stigmatising, durably linked a cuisine to an additive.

What controlled studies show

Since then, trials have given monosodium glutamate or a placebo to people who said they were sensitive. According to the FDA, scientistshave not consistently managed to trigger reactions. A 2000 review published in the Journal of Nutrition (Walker and Lupien) likewise concluded that human studies did not confirm glutamate's involvement in this syndrome.

This does not mean nobody feels anything. The report commissioned by the FDA in the 1990s (FASEB) found that sensitive people could have brief, mild symptoms, such as headaches, numbness or hot flushes, after3 grams or moretaken without food. By comparison, the FDA states that a typical serving of a dish containing added glutamate contains less than 0.5 gram.

EFSA's 2017 re-evaluation

In July 2017, EFSA, the European Food Safety Authority, re-evaluated glutamates E620 to E625. For the first time it set agroup acceptable daily intake (ADI) of 30 mg per kilo of body weight per day, expressed as glutamic acid. It was based on animal studies, as human data did not allow a reference value to be set, for lack of dose-response data.

The panel identified no genotoxicity concern for this group. However, EFSA noted that estimated exposure couldexceed the ADIin some groups:

• people of all ages who eat large amounts of foods containing these additives;
• young children and children with average exposure;
• adding natural sources and nutrients worsens the exceedance in several groups with average or high exposure.

For infants, children and adolescents with very high exposure, intake could also exceed doses linked in humans to certain effects, such as the glutamate symptom complex (from 42.9 mg/kg/day) or headaches (85.8 mg/kg/day). The agency recommendedreviewing the maximum permitted levels, notably for fine bakery products, soups and broths, sauces, meat and meat products, seasonings and food supplements. The general rule today is 10 g per kilo of food, with no numerical ceiling for salt substitutes, seasonings and condiments. We have not checked whether these limits have since been changed.

In other words, the picture is more nuanced than "dangerous" or "risk-free": EFSA does not describe a poison at low doses, but it considers that, for the heaviest consumers, the margin may be exceeded.

Where is it found?

EFSA cites soups and broths, sauces, processed meats, seasonings and condiments among the relevant categories. In practice, added glutamate is often found in:

• stock cubes and dehydrated soups;
• flavoured crisps and snacks;
• ready meals and industrial sauces;
• spice blends and seasonings;
• some charcuterie and meat preparations.

These examples reflect common industry uses and the categories cited by EFSA, and are not an exhaustive list: only the ingredient list of each product is authoritative.

Spotting it on the label: watch out for yeast extracts

Added glutamate as an additive must appear on the label, as "flavour enhancer: monosodium glutamate" orE621(or another number from E620 to E625).

The catch:yeast extracts, hydrolysed vegetable proteins or soy extracts also contain free glutamate, without an E number. According to the FDA, including such ingredients prevents a product from being labelled "no added glutamate" in the United States. In Europe, a "no flavour enhancers" claim only means that no glutamate salt has been added, not that the product is free of glutamate (source: trade press, to be taken as commentary rather than regulatory text). We have not been able to consult the exact European legal text on this point.

A marker of a heavily seasoned product, in Yumiq

A flavour enhancer is used to make a recipe tastier, often with bland base ingredients or a shorter cooking time. Its presence is therefore anindicator of a heavily seasoned, processed product, more than proof of danger: at usual doses, the agencies have not shown a risk for the general population, but EFSA recommends caution with high exposures.

In Yumiq, the product page shows the number of additives detected and sorts them into harmless, to watch and high risk. The Yumiq-Score penalises controversial additives assessed by EFSA and ANSES, and the Yumiq star requires the absence of high-risk additives. The most useful thing is still to look at the whole ingredient list, and to ask how often you eat this type of product.

Sources

• EFSA - Glutamates added to food: re-evaluation (press release, 12 July 2017)
• EFSA - Re-evaluation of glutamic acid (E 620) and its salts (E 621-625) as food additives (EFSA Journal, 2017)
• FDA - Questions and Answers on Monosodium glutamate (MSG)
• van Sadelhoff et al. - Free Amino Acids in Human Milk (Frontiers in Immunology, 2020)
• Walker and Lupien - The safety evaluation of monosodium glutamate (Journal of Nutrition, 2000)
• Food News International - Yeast extracts and labelling (trade press, supplementary)
• Science History Institute - Mass psychosis in food science (trade press, supplementary on the 1968 letter)