Fumaric acid
A naturally occurring organic acid used in small amounts to sharpen sourness and stabilise acidity in food and drinks.
What is it?
Fumaric acid is a simple four-carbon dicarboxylic acid found naturally in many plants, particularly fumitory (Fumaria officinalis, which gives the acid its name), as well as in bolete mushrooms, lichen, and some fruits. The body also produces it as part of the Krebs cycle, the metabolic pathway cells use to generate energy. For food use it is manufactured synthetically via catalytic isomerisation of maleic acid. It appears as a white crystalline powder with a sharp, fruity-sour taste.
What does it do?
Fumaric acid lowers the pH of food, acting as an acidulant and acidity regulator. Because it is the strongest food acid by weight (more acidic per gram than citric or tartaric acid), only small quantities are needed to achieve a tart flavour or to bring a product into an acidic pH range that inhibits microbial growth and oxidation. It also acts as a dough conditioner in baked goods, improving gluten strength, and as a leavening acid that reacts slowly with sodium bicarbonate to produce carbon dioxide during baking.
Where you will see it
Found mainly in baked goods such as tortillas, flatbreads, biscuits, and cake mixes; in fruit-flavoured drinks and powdered soft-drink mixes; in gelatin desserts; in some wines as an acidulant or tartrate-stabilising agent; and in certain sweets and confectionery. On UK ingredient labels it appears as 'fumaric acid' or 'E297'.
What the science says
Body's own metabolite: ordinary exposure context
Fumaric acid is an endogenous compound produced continuously by every human cell as part of normal energy metabolism. Dietary intake from food use adds a small amount on top of what the body makes internally. Because the compound is metabolised through normal pathways, it does not accumulate in tissue under normal dietary exposure.
Fumaric acid is an intermediate of the citric acid (Krebs) cycle and is present in all aerobic organisms, including the human body, where it is continuously synthesised and metabolised.
High-dose animal studies: kidney effects at extreme levels
Rat studies feeding very high doses of fumaric acid, far above any realistic dietary exposure, found kidney changes including nephrocalcinosis (calcium deposits in the kidney). These effects were dose-dependent and were not observed at lower doses more in keeping with food-use levels. Regulatory bodies have used these findings to derive ADI estimates but have not flagged them as a concern at actual food use.
High dietary doses of fumaric acid in long-term rat studies produced nephrocalcinosis and growth retardation; no-observed-adverse-effect levels were established well above typical human dietary exposure from food additives.
Re-evaluation: EFSA called for new data
EFSA issued a call for data on fumaric acid as part of its systematic re-evaluation programme for all previously authorised food additives. This is a routine process required for every approved additive and does not indicate a specific new safety concern. The re-evaluation had not concluded at the time this record was compiled.
EFSA opened a call for data on fumaric acid (E297) and succinic acid (E363) as part of the mandatory re-evaluation programme under Regulation (EU) No 257/2010.
Medical use at much higher doses: a separate context
Fumaric acid esters, particularly dimethyl fumarate, are used as pharmaceutical treatments for psoriasis and multiple sclerosis at doses many times higher than any food additive use. Side effects at therapeutic doses, including flushing and gastrointestinal upset, are not relevant to trace food additive use, but the medical literature sometimes creates confusion between the two contexts.
Dimethyl fumarate (a fumaric acid ester, not fumaric acid itself) is approved as a pharmaceutical for relapsing-remitting multiple sclerosis; side effects at therapeutic doses include flushing and gastrointestinal effects, occurring at exposures far above food-use levels.
Where it stands with the regulators
Who should be careful
No specific population needs to avoid fumaric acid at food-additive levels. People with rare metabolic disorders affecting the citric acid cycle (such as fumarase deficiency) should seek individual medical advice about organic acid intake. Look for 'fumaric acid' or 'E297' in the ingredients list.
The honest read
Fumaric acid is one of the more straightforward food additives. It is a compound the body makes itself, found in many plants, and used in food in small quantities. The animal studies that raised kidney effects used doses far beyond anything a person would encounter through food. The EFSA re-evaluation is routine rather than a response to any new concern. The main scientific uncertainty is simply the completion of the formal re-evaluation, which will either confirm the current status or propose revised conditions. There are no contested population studies, no IARC classification, and no ban or restriction anywhere the additive is used.
Related additives
Common questions
Is E297 banned in the UK?
No. Fumaric acid is an approved food additive in both the UK and the EU. It appears on the UK FSA approved-additives list and is permitted under assimilated EU Regulation 1333/2008.
Is E297 the same as the MS drug dimethyl fumarate?
No. Dimethyl fumarate is a chemical ester of fumaric acid used as a pharmaceutical at high therapeutic doses for multiple sclerosis and psoriasis. Fumaric acid itself (E297) is a different compound used in tiny food quantities as an acidulant. The two are related in name and chemistry but are not interchangeable, and the side effects of the drug do not apply to the food additive.
What foods contain E297?
Most commonly found in tortillas, flatbreads, biscuits, cake mixes, powdered fruit-drink mixes, gelatin desserts, some confectionery, and wine. Check the ingredients list for 'fumaric acid' or 'E297'.
Is E297 vegan?
Yes. Fumaric acid is produced synthetically from maleic acid and contains no animal-derived ingredients. It is also found naturally in many plants. It is suitable for vegan and vegetarian diets.
Sources
- UK FSA Approved Additives and E Numbers
- EFSA Call for Data: Re-evaluation of fumaric acid (E297) and succinic acid (E363) as food additives
- EU Regulation 1333/2008 on food additives (Annex II: Authorised food additives)
- JECFA evaluation of fumaric acid
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