E-numbers / Preservatives / E280
also: Propanoic acid · E280
A naturally occurring acid used as a mould inhibitor in bread, baked goods and some cheeses. New research links it to metabolic changes that may raise insulin resistance.
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Even at levels found in a single serving of preserved bread, propionate raises glucagon and other hormones that oppose insulin.
Why it’s worth knowing. Even at levels found in a single serving of preserved bread, propionate raises glucagon and other hormones that oppose insulin. Repeated daily intake from processed bread and baked goods may contribute to insulin resistance over time.
Propionic acid is a short-chain fatty acid that occurs naturally in small amounts in some fermented foods, particularly Swiss-type cheeses. As a food additive it is produced by fermentation or chemical synthesis and used in its pure acid form (E280) or as sodium, calcium, or potassium propionate salts (E281, E282, E283). It has a slightly pungent, cheesy odour at high concentrations.
Propionate lowers the pH of baked goods and creates conditions that inhibit the growth of mould and certain bacteria, particularly rope-forming Bacillus species that cause bread to become stringy and inedible. Because it works best at the mildly acidic pH of bread dough, it is well matched to that application. It extends shelf life without significantly altering flavour at the amounts permitted in food.
Most commonly found in pre-packaged bread and rolls, particularly medium-sliced and wholemeal loaves sold in UK supermarkets, wrapped crumpets, malt loaves, and some processed cheeses. It also appears in a small number of prepacked cakes and pastries. On a UK ingredient label it may be listed as 'propionic acid', 'E280', or in the salt forms as 'calcium propionate (E282)' or 'sodium propionate (E281)'.
A randomised, placebo-controlled crossover study gave 28 healthy volunteers a dose of calcium propionate comparable to a typical commercial bread serving and measured hormone levels. Propionate significantly raised glucagon, norepinephrine, and fatty acid binding protein 4 (FABP4), all of which oppose the action of insulin. The same study found parallel effects in mice, including elevated glucose production by the liver. A follow-up study in 2021 found acute impairment of glucose metabolism in humans at dietary exposure levels. Researchers described it as a potential metabolic disruptor.
Propionate at doses comparable to a typical preserved-bread serving raised glucagon, norepinephrine, and FABP4 in healthy humans in a randomised controlled trial, increasing endogenous glucose production in a pattern consistent with insulin resistance.
A follow-up human study found that acute ingestion of propionic acid at food-additive exposure levels impaired glucose metabolism, adding to concerns about chronic dietary exposure in populations eating preserved bread daily.
Mouse studies alongside the human RCT showed that chronic propionate exposure led to weight gain, hyperinsulinemia, and insulin resistance, prompting calls for the FDA and food regulators to re-examine the additive.
The European Food Safety Authority completed a full re-evaluation of propionic acid and the propionate salts in 2014. EFSA found no evidence of genotoxicity or carcinogenicity and established an acceptable daily intake of 3mg per kilogram of body weight per day. The panel noted that typical food exposures fall within this limit for most consumer groups, though high bread consumers may approach it. The 2019 and 2021 human metabolic studies post-date this evaluation and have not yet been incorporated into a formal EFSA or UK FSA regulatory review.
EFSA's re-evaluation found no genotoxic or carcinogenic concern and established an ADI of 3mg per kg body weight per day for propionic acid and its salts combined.
High-level bread consumers, including some children, may have dietary exposures to propionates approaching the ADI when total intake from all sources is combined.
Some researchers have investigated propionate as a gut-derived neuroactive compound, noting that it is produced in large quantities by certain gut bacteria and can cross into the bloodstream and brain. Animal studies have shown that injecting large doses of propionate into rat brains produces repetitive behaviours resembling autism. These are high-dose injection studies, not dietary exposure studies, and the link to dietary propionate from food additives in humans remains speculative and unestablished.
Infusion of propionate directly into rat brains induced repetitive motor behaviours and social deficits in high-dose animal studies, leading some researchers to hypothesise a gut-brain propionate pathway relevant to autism. These findings do not apply directly to oral food-additive exposure.
People managing blood sugar, type 2 diabetes, or insulin resistance who eat large quantities of commercial bread or baked goods daily may wish to note that propionates are present in most wrapped bread. Look for 'propionic acid', 'E280', 'calcium propionate', 'E282', 'sodium propionate', or 'E281' in the ingredients list. Bread baked without these additives will typically have a shorter shelf life.
Propionic acid has been in commercial bread for decades and EFSA's 2014 review found no genotoxic or carcinogenic concern. However, two controlled human studies published after that review, in 2019 and 2021, found that doses comparable to those from a single serving of commercial bread raised hormones that oppose insulin action. These are short-term mechanistic studies and do not establish whether daily bread eating causes diabetes. But they are randomised controlled trials in healthy people, which is a stronger design than most food-additive research. The long-term metabolic implications of chronic low-level propionate intake from preserved bread are genuinely unknown. Regulators have not yet formally revisited the ADI in light of this data.
No. Propionic acid (E280) and its salts (E281, E282, E283) are approved food additives in the UK under the assimilated EU Regulation 1333/2008 and the UK FSA approved-additives list. They are widely used in commercial bread and baked goods.
Two randomised controlled trials, published in 2019 (Science Translational Medicine) and 2021 (BMJ Open Diabetes Research and Care), found that propionate raised glucagon and other insulin-opposing hormones in healthy adults at doses similar to those from a normal portion of commercial bread. Whether this translates into long-term harm from daily exposure has not been established.
Most wrapped and pre-sliced bread sold in UK supermarkets, including wholemeal and seeded varieties. Also crumpets, malt loaves, some cakes and pastries, and processed cheese products. It is typically listed as 'propionic acid (E280)', 'calcium propionate (E282)', or 'sodium propionate (E281)'.
Yes. Commercially produced propionic acid used as a food additive is manufactured by fermentation or chemical synthesis, not derived from animal sources.
Last reviewed: 20 June 2026
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