E-numbers / Flavour enhancers / E626

Guanylic acid

also: 5'-Guanylic acid · Guanosine 5'-monophosphate · GMP · 5'-GMP

A purine nucleotide added to boost umami flavour. Typically derived from yeast, fish or meat. People with gout should watch for it.

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E626Flavour enhancer

Guanylic acid

Purines are broken down to uric acid in the body.

What guanylic acid is, what it does and where you will see it

Why it’s worth knowing. Purines are broken down to uric acid in the body. Regular intake from multiple nucleotide enhancers can raise uric acid levels, which may trigger gout attacks in people who are already prone.

What is it?

Guanylic acid (also called guanosine-5'-monophosphate or GMP) is a naturally occurring purine nucleotide. In food production it is isolated from yeast extract, dried fish (especially sardines and anchovies), or meat. It is one of four related nucleotide flavour enhancers listed under E626 to E629, which share the same active compound in different salt forms.

What does it do?

GMP binds to umami taste receptors on the tongue and dramatically amplifies the savoury signal, particularly when combined with glutamates such as monosodium glutamate (E621). Used together, the two compounds have a synergistic effect: the perceived flavour intensity is far greater than either produces alone. This allows manufacturers to use less total flavouring to hit a target taste profile.

Where you will see it

Instant noodles and cup soups, stock cubes and bouillon powders, flavoured crisps and snack seasonings, ready meals with savoury sauces, processed meat products, and Asian condiments such as oyster sauce and soy-based seasoning blends. On a label it appears as 'guanylic acid', 'E626', or grouped under 'flavour enhancers (E626, E627, E631)' in the ingredients list.

What the science says

Purines and uric acid

Guanylic acid is a purine compound. When digested, purines are converted to uric acid. People whose kidneys clear uric acid slowly can accumulate high blood levels, a condition called hyperuricaemia, which can crystallise in joints and trigger gout. Nucleotide additives from food contribute to total purine load alongside purines from meat, offal, and beer. UK and international dietary guidance for gout advises limiting high-purine foods and additives.

Dietary purine intake, including from nucleotide flavour enhancers, raises serum uric acid levels. High serum uric acid is the primary driver of gout and urate crystal deposition in joints.

EstablishedNHS UK: Gout dietary guidance

The EFSA Panel on Food Additives and Nutrient Sources (ANS) evaluated guanylic acid and its salts (E626-E629) and concluded they are metabolised as purines. No numerical ADI was set because the compounds are endogenous nucleotides handled by normal purine metabolism.

2016Regulatory reviewEFSA ANS Panel, re-evaluation of nucleotide flavour enhancers E626-E629

Dietary source and allergen risk

Most commercial guanylic acid is produced by fermenting yeast or by hydrolysis of fish (particularly sardines and anchovies) or meat. This means the additive is rarely vegan or vegetarian. It may also carry trace fish proteins. People with fish allergies should treat E626 with caution unless the label confirms a plant or yeast-only source.

Guanylic acid and its salts are commonly derived from fish or animal tissues. Fish is a declarable allergen under UK food labelling law (UK Food Information Regulation, assimilated from EU 1169/2011). Where the additive is fish-derived, the source allergen must be declared.

2014RegulatoryUK Food Information Regulations 2014 (assimilated EU Regulation 1169/2011, Annex II)

No evidence of toxicity at food-use levels

Outside the purine-metabolism pathway, guanylic acid has not been linked to toxic effects at the quantities found in food. Regulatory bodies have not set a numerical ADI on safety grounds; the absence of an ADI reflects that the compound is treated as a normal metabolite rather than a foreign chemical, not that concerns were set aside.

EFSA found no evidence of genotoxicity, carcinogenicity or reproductive toxicity for guanylic acid and its salts at typical food use levels.

2016Regulatory reviewEFSA ANS Panel opinion on E626-E629

Where it stands with the regulators

Approved for use in the UK and EU

Legal basis: UK FSA approved-additives list (authorised in England, Scotland and Wales as of 31 December 2020) and assimilated EU Regulation 1333/2008, Annex II
Permitted foods: Seasonings and condiments; Soups and broths; Sauces; Processed and canned meat and fish products; Flavoured snack products; Instant noodle and dried soup mixes; Ready meals
Maximum levels: Varies by food category; typically used at quantum satis (as much as needed) within permitted categories
Safe-intake limit (ADI): No numerical ADI set (metabolised via normal purine pathways)
History: E626 and its salt forms E627-E629 have been permitted in the EU and UK for decades as part of the nucleotide flavour enhancer group. EFSA re-evaluated the group in 2016 and maintained their authorisation, concluding that available data did not raise a safety concern at current use levels, while noting the compounds are metabolised as purines. No restrictions or bans have been applied.

Who should be careful

People with gout, hyperuricaemia (high uric acid), or kidney stones made of urate crystals should limit intake of all purine-rich additives. Look for 'guanylic acid', 'E626', or the broader flavour enhancer cluster 'E626-E631' in the ingredients list. People with fish allergies should check whether the source is fish-derived; where it is, the label must declare 'fish' in the allergen information. Strict vegetarians and vegans should avoid it unless the label or manufacturer confirms a plant or fermentation source.

The honest read

E626 is a well-established additive that has been in processed food since the mid-twentieth century, when Japanese food scientists identified nucleotides as the molecules behind the umami taste of fermented and dried fish. The regulatory science is straightforward: no toxicity signals, no carcinogen classification, no bans. The one real and well-documented issue is purine load. For most people eating it occasionally this does not register, but for the roughly 1 in 40 UK adults who have gout or are prone to it, every source of dietary purines matters and nucleotide additives are a legitimate thing to watch. The fish-allergen and vegan questions are also real and not always easy to resolve from a short ingredients list alone.

Common questions about guanylic acid

Is E626 banned in the UK?

No. E626 is approved for use in the UK. It is authorised under the UK FSA approved-additives list, which assimilated EU Regulation 1333/2008, and has been continuously permitted since the UK left the EU.

Can E626 trigger a gout attack?

It can contribute to one. E626 is a purine compound, and purines are broken down to uric acid in the body. People with gout are advised to limit all dietary purines, including those from additives such as E626, E627, E628, E629 and E630. If you have gout, check ingredient lists for any of these E numbers.

What foods contain E626?

Instant noodles, cup soups, stock cubes, flavoured crisps, ready meals, processed meat, and Asian sauces are the most common sources. It almost always appears alongside glutamates and the related nucleotides E627 or E631, so look for the full flavour-enhancer cluster in the ingredients.

Is E626 vegan?

Usually not. Most commercial guanylic acid is produced from yeast extract, dried fish such as sardines or anchovies, or meat tissue. Vegan products exist but they are the exception. If the packaging carries no vegan certification, contact the manufacturer to confirm the production source before consuming.