E-numbers / Flavour enhancers / E628
also: Dipotassium 5'-guanylate · Potassium guanylate
A potassium salt of guanylic acid used to amplify savoury umami taste. Always appears alongside other flavour enhancers in processed snacks and soups.
Scan a barcode to check a food for dipotassium guanylate. NutraSafe Pro · £3.99/month · iOS
Guanylates are broken down in the body to purines, which raise uric acid levels.
Why it’s worth knowing. Guanylates are broken down in the body to purines, which raise uric acid levels. People with gout or high uric acid should avoid regular intake of guanylate-containing foods.
Dipotassium guanylate is the dipotassium salt of guanosine 5'-monophosphate (GMP), a naturally occurring nucleotide. It belongs to the guanylate family of flavour enhancers (E626-E629), which also includes disodium guanylate (E627). Commercial production uses yeast extract fermentation or enzymatic hydrolysis of RNA from yeast or dried fish, then treated with potassium hydroxide to form the potassium salt.
GMP is a nucleotide that binds to umami taste receptors (the T1R1/T1R3 heterodimer on the tongue) and dramatically amplifies the umami signal produced by glutamates such as monosodium glutamate (MSG, E621). At typical use levels it has little taste of its own; the effect is synergistic, meaning a small amount of guanylate alongside MSG produces a far stronger umami sensation than either alone. This allows manufacturers to use less MSG while achieving the same flavour impact.
Found primarily in processed savoury products: instant noodles, packet soups, flavoured crisps and snack foods, dry seasonings, bouillon cubes, ready meals, fast-food sauces and gravies. Almost always used in combination with disodium inosinate (E631) or monosodium glutamate (E621). On UK ingredient labels it appears as 'flavour enhancer (628)', 'dipotassium guanylate', or 'E628'.
Guanylates are nucleotides that the body breaks down into purines, ultimately producing uric acid. At food-use concentrations the contribution to dietary purine load is modest, but for people already prone to high uric acid the cumulative effect of regularly eating guanylate-enriched processed foods is relevant. Gout attacks are triggered by uric acid crystals forming in joints, so clinicians advise people with gout to limit all high-purine sources including nucleotide additives.
Dietary purines, including those from guanylate nucleotides, are metabolised to uric acid via xanthine oxidase; elevated serum uric acid is a direct driver of gout and can worsen hyperuricaemia in susceptible individuals.
The European Food Safety Authority notes that guanylates are generally used at low levels and that no numerical ADI has been set; however, they acknowledge that individuals with conditions affecting purine metabolism should treat guanylate-containing foods with caution.
Commercial guanylates can be derived from dried fish (sardines or bonito) as well as from yeast RNA. Fish-derived production means the additive is not vegetarian or vegan unless the manufacturer specifies a yeast or fermentation source. This is not declared on UK labels; the source is not required to be stated alongside the E number.
Guanylates (E626-E629) may be produced from either yeast RNA or from fish-derived sources (sardines, bonito flakes); source is not mandated on the product label under UK/EU food information law.
The synergistic effect between guanylates and glutamates is well-characterised. GMP can amplify the perceived umami intensity several-fold when combined with glutamate, allowing manufacturers to reduce glutamate levels. There is no established health concern arising from this synergistic mechanism itself.
GMP and IMP (inosine 5'-monophosphate) act as positive allosteric modulators of the T1R1/T1R3 umami receptor, amplifying glutamate-induced responses by factors of 5 to 30 depending on concentration.
People with gout, hyperuricaemia, or a history of uric acid kidney stones should limit intake. Look for 'E628', 'dipotassium guanylate', or 'flavour enhancer (628)' on the label. Vegetarians and vegans should note that the fish-derived production route is not disclosed on UK labels; if in doubt, contact the manufacturer.
The purine concern is well-established biochemistry, not a contested fringe claim: nucleotides convert to uric acid, uric acid causes gout. At normal snack-food quantities the guanylate contribution to total dietary purine load is small compared with a serving of red meat or seafood. For most people, the additive registers as an unremarkable processing tool. For the minority who already track purines, it is one more item to count. The source ambiguity (fish versus yeast) is a genuine labelling gap for vegetarians that UK law does not currently require manufacturers to close.
No. Dipotassium guanylate (E628) is approved under the UK FSA's list of permitted food additives, carried over from EU Regulation 1333/2008.
Guanylates are metabolised to purines and then to uric acid, which drives gout. People managing gout or high uric acid are generally advised by clinicians to limit all dietary purine sources, including guanylate-containing processed foods.
Instant noodles, packet soups, flavoured crisps, dry seasoning sachets, bouillon cubes, ready meal sauces, and savoury crackers. It almost always appears alongside E621 (MSG) or E631 (disodium inosinate).
Not reliably. Dipotassium guanylate can be produced from dried fish (such as sardines or bonito) or from yeast RNA fermentation. UK labels are not required to state the production source, so vegan status cannot be confirmed from the ingredient list alone.
Last reviewed: 20 June 2026
It's the only app that does thisUKJaneK
You Need This AppGmac2005
Best AppGK getting skinny UK App Store reviews
NutraSafe reads the label and puts every additive into plain English, with the source, right in the app.
NutraSafe Pro · £3.99/month · iOS
