E-numbers / Preservatives / E238
also: Calcium methanoate · Formic acid calcium salt
The calcium salt of formic acid. Not authorised as a food additive for human consumption in the UK or EU. Approved only for animal feed.
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E238 is not a permitted food additive for human food in the UK or EU.
Why it’s worth knowing. E238 is not a permitted food additive for human food in the UK or EU. If you see it on a label of food intended for people, that food should not be on sale. Its parent compound, formic acid, inhibits a key cellular energy enzyme at high concentrations.
Calcium formate is the calcium salt of formic acid, a simple organic acid that occurs naturally in ant venom and some plant tissues. It forms white crystalline granules. Under the E238 designation it is authorised in Great Britain as a preservative in animal feed, but it does not appear on the UK or EU positive list of approved food additives for human consumption.
As a preservative it works by acidifying its environment, lowering pH enough to inhibit the growth of bacteria, moulds and yeasts. In animal feed it is used to reduce microbial load and stabilise feed during storage. In the body, formate ions (released when formic acid or its salts are metabolised) are cleared by folate-dependent pathways in the liver. At very high concentrations, formate inhibits cytochrome c oxidase, the key enzyme driving cellular energy production.
E238 should not appear in any food product intended for human consumption sold in the UK or EU. Its main legitimate uses are in animal feed (pig and poultry feed acidification, stabilisation of silage and total mixed rations), concrete and cement as a setting accelerator, de-icing formulations, and leather processing. On a human food label, the presence of E238 would indicate a non-compliant product.
EU Regulation 1333/2008 operates on a positive-list principle: only additives explicitly listed in Annex II may be used in food for human consumption. E238 does not appear in Annex II. The list jumps from E235 (natamycin) to E239 (hexamethylene tetramine), with no entry for E236, E237 or E238. The UK FSA approved-additives list, which mirrors this regulation as retained law, similarly contains no authorisation for calcium formate in human food. Its only UK regulatory status is as an authorised animal feed additive (FSA feedadd-48, Article 10 authorisation for all animal species).
E238 calcium formate does not appear in Annex II of EU Regulation 1333/2008 or on the UK FSA approved-additives list for human food.
E238 is authorised in Great Britain as a technological feed additive (preservative) for all animal species under Commission Directive 85/429/EEC as retained and updated.
Calcium formate releases formate ions when dissolved. In the body, formate is a normal metabolic intermediate, present in blood at low levels. At very high concentrations, as seen in acute methanol poisoning, accumulated formate inhibits cytochrome c oxidase (the enzyme driving mitochondrial energy production), causing metabolic acidosis, optic nerve damage and, in severe cases, death. These effects occur at blood formate concentrations far above anything produced by ordinary dietary sources. JECFA set a group ADI of 0 to 3 milligrams per kilogram bodyweight for formic acid and its ethyl ester when used as a flavouring, maintained at the 49th meeting in 1997.
Formate inhibits cytochrome c oxidase, the terminal enzyme of the mitochondrial electron transport chain, contributing to metabolic acidosis and optic nerve injury in methanol poisoning.
JECFA established a group ADI of 0 to 3 mg/kg bodyweight for formic acid and ethyl formate, maintained at the 49th JECFA meeting; the context is use as a flavouring agent at low levels.
EFSA's FEEDAP Panel evaluated calcium formate as a feed preservative in 2015 and again in 2020. The 2015 opinion found no discernible effect on microbial numbers in feed. The 2020 reassessment, based on new in vitro data, concluded it has potential efficacy as a preservative in feedingstuffs. Both opinions found no safety concern for consumers eating food from animals given the additive at approved feed levels. EFSA noted it is non-irritant to skin but mildly irritant to eyes and a respiratory sensitiser for farm workers handling it.
EFSA FEEDAP Panel concluded calcium formate has potential to be efficacious as a preservative in animal feedingstuffs; no consumer safety concern was identified at the approved inclusion levels.
Because E238 is not an authorised food additive in the UK or EU, no person should encounter it in a legally sold human food product. If you see E238 or 'calcium formate' listed in the ingredients of a food product, that product may not comply with food law and you can report it to the UK FSA. There is no specific population group singled out as more sensitive, because the substance should not be present at all.
E238 occupies an unusual position: it has an E-number, which many people associate with approved food additives, but in the UK and EU the number was assigned in the context of animal feed regulation, not human food. No safety evaluation for use in human food has been completed by EFSA or the UK FSA for the preservative function. The toxicological concern with formate at very high concentrations, principally from methanol poisoning studies, was part of the backdrop to the substance never making the positive list. Whether the exclusion was driven primarily by toxicological caution, lack of industry application dossiers, or simply the availability of alternative approved preservatives is not publicly documented in regulatory records. The position of the science is that formate is a normal metabolite at low levels, and toxic at high acute concentrations, but the gap between normal metabolism and harmful levels is large. What is clear is that the regulatory gatekeeping worked as intended: the substance is simply not on the list of permitted human food additives.
E238 calcium formate is not on the UK FSA approved-additives list for human food. Under UK food law, which operates on a positive-list principle, only additives explicitly authorised may be used. E238 is not authorised for any human food category, so its use in food for people is not permitted. It is authorised separately as an animal feed additive.
E-numbers are used in both human food regulation and animal feed regulation in the UK and EU. E238 received its designation in the context of animal feed legislation, where it is an authorised preservative. Having an E-number does not automatically mean an additive is approved for human consumption.
No human food product sold legally in the UK or EU should contain E238. Its authorised uses are in animal feed, concrete production, de-icing formulations and leather processing. If you see E238 on the label of a food intended for human consumption, that product may not comply with UK food law.
Calcium formate is a synthetic inorganic salt and does not contain animal-derived ingredients. However, because E238 is not an authorised food additive for human food in the UK or EU, the vegan status question is largely academic: it should not appear in any food product on UK shelves.
Last reviewed: 20 June 2026
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