TBHQ
A synthetic antioxidant added to fats and oils to delay rancidity. Animal studies linked it to tumours; genotoxicity tests are mixed.
Animal studies found stomach tumours at higher doses and DNA-damaging effects in cell tests. The EU and UK retain a low acceptable daily intake, and EFSA noted data gaps in its 2016 review.
What is it?
Tertiary-butyl hydroquinone (TBHQ) is a white crystalline powder synthesised from hydroquinone and isobutylene. It belongs to the same family as BHA (E320) and BHT (E321) and is used as a fat-soluble antioxidant in food processing.
What does it do?
TBHQ interrupts the chain reaction of lipid oxidation by donating a hydrogen atom to free radicals, neutralising them before they can degrade fats and oils. This slows rancidity, extends shelf life, and preserves flavour and colour in fatty foods.
Where you will see it
Most commonly used in frying oils, fast-food cooking oils, instant noodles, microwave popcorn, crackers, crisps, peanut butter, and some margarines and shortenings. It also appears in some dried meats and fish products. On a UK label it appears as E319 or tertiary-butyl hydroquinone.
What the science says
Animal tumour findings
In long-term rodent feeding studies, TBHQ was associated with the development of stomach tumours (forestomach squamous-cell carcinomas) in rats and mice at high doses. Regulatory agencies consider these findings relevant to the hazard assessment but note the doses far exceeded typical human dietary exposure. The forestomach is not a direct analogue of the human stomach, which complicates direct extrapolation, but the findings were sufficient for regulators to retain a strict ADI.
Long-term rat and mouse studies found forestomach tumours at high dietary concentrations of TBHQ, leading EFSA to retain a conservative acceptable daily intake.
Genotoxicity: mixed picture
In laboratory tests, TBHQ has shown both positive and negative results for genotoxicity depending on the test system and dose. Some in-vitro cell studies have found DNA strand breaks and chromosomal damage at concentrations above those expected from normal food intake. In-vivo animal genotoxicity tests have generally been negative. EFSA concluded the overall genotoxicity profile was unclear and flagged it as a concern requiring further data.
EFSA's 2016 re-evaluation identified genotoxicity data gaps and could not fully rule out genotoxic potential, noting positive results in some in-vitro assays.
A 2024 cell-study review found cytotoxic and genotoxic effects of TBHQ and related synthetic antioxidants at doses absorbed via the gastrointestinal tract, though in-vivo data remain limited.
Neurological effects in high-dose animal studies
At doses substantially above estimated human intake, some rodent studies reported neurological effects including convulsions. These findings contributed to the basis for the ADI. No equivalent human data exist at dietary exposure levels.
High-dose animal studies reported neurotoxic effects including convulsions, providing additional input to the ADI calculation for TBHQ.
Human exposure vs. ADI
Estimated dietary exposure to TBHQ in UK and EU populations sits well below the ADI at average intakes, but high consumers of fried and processed snack foods, particularly children, may approach the ADI more closely. EFSA's 2016 review could not fully rule out exceedance in high-intake children due to data gaps in use levels.
EFSA dietary exposure estimates for high-consuming children could not exclude ADI exceedance, partly due to incomplete use-level data from industry.
Where it stands with the regulators
Who should be careful
People who regularly eat large quantities of fried snacks, instant noodles, or processed crackers should be aware that TBHQ accumulates across those products. Children who eat a lot of processed snack foods may be closer to the intake limit than the average adult. Look for E319 or tertiary-butyl hydroquinone in the ingredients list.
The honest read
TBHQ sits in an uncomfortable middle ground. It is approved, but the science supporting that approval has acknowledged holes. The main animal evidence, stomach tumours in rodents, is real and the basis for the strict ADI. The genotoxicity picture is genuinely unsettled: some cell tests are positive, in-vivo tests less so. Regulators allowed it to stay on the market at restricted levels, with EFSA explicitly noting it could not fully close the genotoxic question in 2016. The additive is far more prevalent in US food than in UK or EU food, so UK shoppers see it mainly in imported snacks, fast-food oils, and some instant noodles. The science here is live, not settled.
Related additives
Common questions
Is E319 banned in the UK?
No. E319 is permitted in the UK under the assimilated EU Regulation 1333/2008 and is on the FSA's approved-additives list. It is subject to specific maximum levels by food category and is not permitted in foods for infants and young children.
Did EFSA find any safety concerns when it re-evaluated TBHQ?
Yes. In its 2016 re-evaluation, EFSA flagged animal tumour data and could not fully rule out genotoxic potential based on some positive in-vitro results. It set a conservative acceptable daily intake of 0.7mg/kg body weight per day and noted that high-consuming children could not be confirmed to stay within it due to incomplete data.
What foods contain E319?
In the UK you are most likely to find E319 in imported processed snacks, instant noodles, crackers, and frying oils used in fast food. It is more common in US-origin products. Check the ingredients list for E319 or tertiary-butyl hydroquinone.
Is E319 vegan?
Yes. TBHQ is synthesised from petrochemical-derived compounds and does not involve animal products or animal testing in its production. It is considered vegan.
Sources
- FSA Approved Additives and E Numbers
- EFSA ANS Panel: Re-evaluation of tertiary-butyl hydroquinone (E 319) as a food additive (EFSA Journal 2016;14(12):4667)
- Esazadeh et al. - Cytotoxic and genotoxic effects of tert-butylhydroquinone, butylated hydroxyanisole and propyl gallate as synthetic food antioxidants (Food Science and Nutrition, 2024)
- EU Regulation 1333/2008 on Food Additives (Annex II)
Aaron Keen is the founder of NutraSafe. He researches and writes every additive entry himself, from the primary sources. About the research →
This is a guide, not medical advice. If an additive affects you, speak to your GP or a dietitian.
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