Sodium benzoate
A synthetic preservative that stops bacteria, yeast and mould growing in acidic foods and drinks. In drinks that also contain vitamin C it can form small amounts of benzene.
In soft drinks it can react with added vitamin C to form benzene, a known carcinogen, especially with heat or light. It can also trigger reactions in some people with asthma, aspirin sensitivity or chronic hives.
What is it?
The sodium salt of benzoic acid, made industrially. It is one of the oldest and most widely used food preservatives, working best in acidic products like fizzy drinks, fruit juices and pickles.
What does it do?
It is bacteriostatic and fungistatic in acidic conditions: as the food's acidity lets it enter microbial cells, it lowers the internal pH and stalls the energy production bacteria, yeasts and moulds need to grow.
Where you will see it
Found in acidic soft drinks and energy drinks, fruit juices and squashes, pickles, sauces, salad dressings, jams and some confectionery. On a label it appears as 'sodium benzoate' or 'E211', usually in the preservative line.
What the science says
Benzene formation with vitamin C in drinks
When sodium benzoate and ascorbic acid (vitamin C) are both present in a drink, they can react to form benzene, which is a known human carcinogen. Heat and light speed the reaction up. Regulators tested this directly in the 2000s: most products were low, but a small number exceeded the drinking-water limit before being reformulated. This is a manufacturing and formulation issue, not a property of the additive eaten on its own.
Benzene can form at low levels in beverages containing both benzoate salts and ascorbic acid; heat and light promote it.
FDA analysed almost 200 beverage samples between 2005 and 2007; 10 contained benzene above 5 ppb (the drinking-water limit). All 10 were reformulated or discontinued, with reformulated products then below 1.5 ppb.
Benzene is classified as carcinogenic to humans (Group 1).
Hyperactivity in children (Southampton study)
In the 2007 Southampton study, children drank mixes that combined artificial colours with sodium benzoate, and showed increased hyperactivity. Because benzoate was always given alongside the colours, the study could not separate out how much, if any, came from the benzoate itself. The FSA warning-label rule that followed applies to the six colours, not to E211.
Mixtures of four artificial colours plus sodium benzoate increased hyperactivity in 3-year-old and 8-9-year-old children in the general population.
EFSA judged the study gave limited evidence of a small effect; effects were not consistent across the two age groups or the two mixtures, and benzoate's individual role could not be isolated.
Asthma, hives and sensitivity
A minority of people react to benzoates. Reported reactions include worsening of asthma and episodes of hives (urticaria) and swelling, more often in people who are also sensitive to aspirin. These are individual sensitivities rather than effects expected across the whole population.
Sodium benzoate provoked repeated episodes of acute urticaria and angio-oedema in sensitive individuals under controlled challenge.
Benzoate can worsen asthma in a subset of asthmatic patients, particularly those sensitive to aspirin.
EFSA 2016 re-evaluation and intake
EFSA re-evaluated the benzoates in 2016 and kept the acceptable daily intake at 5 mg/kg of body weight per day, expressed as benzoic acid. It also flagged that, at current usage, intake could exceed this limit for some higher-consuming groups such as children.
EFSA derived an ADI of 5 mg/kg body weight per day (as benzoic acid), from a 500 mg/kg/day no-effect level in a rat reproductive study and a 100-fold uncertainty factor.
Where it stands with the regulators
Who should be careful
People with diagnosed benzoate sensitivity, aspirin sensitivity, chronic urticaria or asthma that flares after preserved drinks should look for 'sodium benzoate' or 'E211' on the label and discuss avoidance with their doctor.
The honest read
Most online 'sodium benzoate causes cancer' claims compress the benzene story. The benzene risk is real but specific: it needs benzoate and vitamin C together in a drink, plus heat or light, and manufacturers reformulated the products that tested high. The hyperactivity link comes from a study where benzoate was always mixed with artificial colours, so its own contribution is unclear.
Related additives
Common questions
Is E211 banned in the UK?
No. It is an authorised preservative in the UK and EU under retained Regulation 1333/2008 and appears on the FSA approved additives register.
Does sodium benzoate form benzene in drinks?
It can, but only when a drink also contains vitamin C (ascorbic acid); heat and light speed it up. FDA surveys in the 2000s found a small number of drinks above the 5 ppb drinking-water limit, and those products were reformulated or withdrawn.
What foods contain E211?
Mainly acidic products: soft and energy drinks, fruit juices and squashes, pickles, sauces and dressings, jams and some sweets. It shows as 'sodium benzoate' or 'E211' in the ingredients.
Is E211 vegan?
Yes. Sodium benzoate is made synthetically from benzoic acid and contains no animal-derived material.
Sources
- FSA - Approved additives and E numbers
- EFSA (2016) - Re-evaluation of benzoic acid (E210), sodium benzoate (E211), potassium benzoate (E212), calcium benzoate (E213)
- US FDA - Questions and Answers on the Occurrence of Benzene in Soft Drinks and Other Beverages
- McCann et al. (2007), The Lancet - Food additives and hyperactive behaviour in children
- EFSA (2008) - Assessment of the results of the study by McCann et al. (2007)
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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