Caramel (general)
Brown colouring made by heating sugars, sometimes with ammonia or sulphite compounds. Found in cola, beer, sauces, and spirits.
The ammonia-process versions (E150c and E150d) contain a byproduct called THI that reduced white blood cell counts in animal studies, and another byproduct, 4-methylimidazole, that caused lung tumours in mice and is classified by IARC as a possible carcinogen. Products containing E150b or E150d may also carry residual sulphites, which can trigger breathing difficulties in people with sulphite sensitivity.
What is it?
Caramel colour is a complex dark-brown mixture produced by controlled heat treatment of food-grade carbohydrates such as glucose, fructose, sucrose, or dextrose. Depending on the manufacturing reactants used, it is divided into four classes: E150a (plain, no added chemicals), E150b (made with sulphite compounds), E150c (made with ammonium compounds), and E150d (made with both sulphite and ammonium compounds). Class IV (E150d) accounts for approximately 70% of caramel colouring produced worldwide; Class III (E150c) accounts for around 20-25% of use in the USA and approximately 60% in Europe, making the two ammonia-process classes the dominant commercial forms.
What does it do?
It gives foods and drinks a brown colour ranging from pale straw to near-black. In some applications it also contributes bitter or roasted flavour notes. As a water-soluble liquid or powder it disperses evenly through beverages and sauces without affecting texture.
Where you will see it
Cola and other dark soft drinks (typically E150d), beer and stout, cider, soy sauce, brown sauces, Worcestershire sauce, gravies, dark breads, biscuits, caramel-flavoured confectionery, breakfast cereals, and Scotch whisky (typically E150a). On a UK ingredient label it appears as 'colour (caramel)', 'caramel colour', or 'colour (E150)', sometimes with the specific letter suffix (E150a, E150c, E150d).
What the science says
4-methylimidazole (4-MEI): IARC classification and animal evidence
4-MEI forms as a byproduct when ammonia-based caramel colours (E150c and E150d) are manufactured. The US National Toxicology Program's two-year feeding study found clear evidence of lung tumours in male and female mice, though not in rats. Genotoxicity tests were consistently negative, suggesting a threshold mechanism rather than direct DNA damage. IARC classified 4-MEI as Group 2B, possibly carcinogenic to humans, in 2013, based on the animal data and the absence of human studies.
Two-year NTP feeding study found clear evidence of carcinogenic activity in male and female mice, with increased incidences of alveolar/bronchiolar lung tumours. Results in rats were negative or equivocal.
IARC classified 4-MEI as Group 2B, possibly carcinogenic to humans, based on sufficient animal evidence and no available human data.
Genotoxicity assays for 4-MEI were negative in bacterial mutation tests and micronucleus tests in vivo, suggesting the mouse lung tumours involve a threshold mechanism.
EFSA concluded that the carcinogenic effect of 4-MEI in mice is likely thresholded due to the lack of genotoxicity, and that exposure estimates from caramel colours are not of concern at current use levels.
THI and immune system effects in E150c
Ammonia caramel (E150c) contains a minor constituent called THI (2-acetyl-4-tetrahydroxybutylimidazole). Multiple animal studies found that THI reduces circulating lymphocytes, which are white blood cells central to immune defence. The effect was reversible and appeared dose-dependent. EFSA set a more restrictive acceptable daily intake for E150c specifically because of remaining uncertainties about this immune effect in humans.
THI caused lymphopenia (reduced lymphocyte counts) in mice and rats in a dose-dependent manner, with marked effects at higher doses. The effect was reversible on withdrawal.
THI sequestrates recirculating T lymphocytes in non-lymphoid tissues including liver, lungs and kidneys, suppressing T cell responses in vitro.
EFSA set a separate individual acceptable daily intake of 100 mg per kilogram of body weight per day for E150c, compared to 300 mg/kg bw/day for the group, because of uncertainties around THI's immune effects in animals and the absence of human data.
Sulphite residues in E150b and E150d
E150b (caustic sulphite caramel) and E150d (sulphite ammonia caramel) are manufactured using sulphite compounds. Residual sulphur dioxide can remain in the finished colourant. Under UK and EU allergen law, products must declare sulphites on the label if they are present above 10 mg per kg or per litre in the finished food, whether or not the sulphites serve a technological function in the final product. Sulphite sensitivity can provoke asthma-like symptoms and is recognised as one of the 14 major allergens in UK food law.
E150b and E150d are manufactured with sulphite compounds and may carry residual sulphur dioxide in the finished colourant. EU specification limits set a maximum of 0.2% (2000 ppm) sulphur dioxide in the caramel colourant itself.
Sulphur dioxide and sulphites are declarable allergens in UK food law when present above 10 mg/kg or 10 mg/litre in the finished product. This applies regardless of whether they remain technologically active.
Exposure and ADI exceedance in toddlers
When EFSA first set the acceptable daily intake levels in 2011 it found that toddlers and adults who consume large amounts of foods coloured with E150c could exceed the more restrictive 100 mg/kg/day limit for that class. A refined 2012 assessment using actual use levels rather than maximum permitted levels found overall group exposure was below the 300 mg/kg/day group limit, but toddlers remained a population that could still exceed the E150c individual limit.
In the 2011 assessment, estimated dietary exposure for toddlers and high-consuming adults to E150c exceeded its individual ADI of 100 mg/kg bw/day when maximum permitted use levels were assumed.
A 2012 refined exposure assessment using actual use levels found the group ADI of 300 mg/kg bw/day was not exceeded for any population group, but toddlers could still exceed the E150c-specific ADI of 100 mg/kg bw/day.
Where it stands with the regulators
Who should be careful
People with sulphite sensitivity or sulphite-triggered asthma should check for E150b or E150d specifically, and look for 'sulphites' or 'sulphur dioxide' in the allergen declaration. If only 'colour (caramel)' or 'E150' appears with no letter suffix and no sulphite declaration, the class cannot be determined from the label alone. There is no established human safe limit for THI or 4-MEI from dietary caramel colour exposure, so people who want to reduce exposure to ammonia-process caramel colours should look for E150a (plain caramel) as the only class manufactured without ammonia or sulphite.
The honest read
E150 is one of the most widely consumed food colourings in the world, present in cola, dark beer, sauces, and spirits for decades. The general 'caramel colour' grouping covers four distinct substances made by meaningfully different processes with different byproduct profiles. E150a, plain caramel, has the longest history and the fewest process-related concerns. E150c and E150d are the dominant commercial classes and carry two distinct signals: a byproduct (THI) that suppresses immune cells in animal studies, and another byproduct (4-MEI) that caused lung tumours in mice and earned an IARC Group 2B classification. EFSA reviewed both and concluded the carcinogenic effect is thresholded (not a direct DNA mutation mechanism) and that real-world exposure from food is below the level that caused effects in animals. California's regulators reached a different conclusion on the threshold question and require a Prop 65 warning on products where 4-MEI intake exceeds 29 micrograms per day. The animal immune data on THI were strong enough that EFSA set a more restrictive daily intake limit for E150c than for the other three classes. The science on both THI and 4-MEI is real, peer-reviewed, and contested in regulatory circles. The gap between EFSA's position and California's on 4-MEI reflects a genuine scientific disagreement about mechanism, not a simple difference of opinion on risk tolerance.
Related additives
Common questions
Is E150 banned in the UK?
No. All four classes of caramel colour (E150a, E150b, E150c, E150d) are approved food additives in the UK under the retained version of EU Regulation 1333/2008. They appear on the UK FSA's authorised additives list.
Is the 4-MEI in caramel colour a cancer risk?
4-MEI is found only in E150c and E150d, the two ammonia-process classes. IARC classified it as Group 2B (possibly carcinogenic to humans) in 2013, based on lung tumours in mice. EFSA and FDA both concluded the mouse tumours involve a threshold mechanism and that typical dietary exposure from food is well below the doses that caused animal effects. California's food safety agency reached a different conclusion and requires a warning label on products where daily 4-MEI intake from a single serving exceeds 29 micrograms. These are genuinely different regulatory calls on the same animal data.
What foods contain E150?
Cola and other dark soft drinks (mostly E150d), stout and dark beer (E150c), soy sauce, brown sauce, Worcestershire sauce, gravies, dark breads, some biscuits and breakfast cereals, caramel confectionery, and many blended Scotch whiskies (E150a). It appears on labels as 'colour (caramel)', 'caramel colour', or 'colour (E150)', sometimes with an 'a', 'b', 'c', or 'd' suffix.
Is E150 vegan?
Yes. All four classes are produced from plant-derived sugars. The ammonium and sulphite compounds used as processing aids in E150b, E150c, and E150d are inorganic, not animal-derived. E150 is considered vegan.
Sources
- EFSA ANS Panel: Scientific Opinion on the re-evaluation of caramel colours (E150a-d) as food additives, EFSA Journal 2011, 9(3):2004
- EFSA ANS Panel: Refined exposure assessment for caramel colours (E150a, c, d), EFSA Journal 2012, 10(12):3030
- IARC Monographs Volume 101: Some Chemicals Present in Industrial and Consumer Products, Food and Drinking-Water (4-MEI classified Group 2B)
- NTP Technical Report 535: Toxicology and Carcinogenesis Studies of 4-Methylimidazole in F344/N Rats and B6C3F1 Mice
- Pham et al., Genotoxicity assessment of 4-methylimidazole: regulatory perspectives, Genes and Environment 2016 (PMC5088675)
- Meredith et al., Lymphopenic effects on mice of a component of ammonia caramel (THI), PubMed 3147240
- Whitfield et al., The immunomodulatory compound 2-acetyl-4-tetrahydroxybutyl imidazole causes sequestration of lymphocytes in non-lymphoid tissues, PubMed 9429899
- UK FSA Approved Additives and E Numbers
- UK FSA Regulated Products: E150a (plain caramel) authorisation record
- EU Commission Regulation 505/2014 amending Annex II to Regulation 1333/2008 on use of caramel colours in beer and malt beverages
- NCBI Bookshelf: 4-Methylimidazole chapter from IARC Monographs Vol 101
- CA OEHHA Proposition 65: 4-Methylimidazole - No Significant Risk Level (NSRL) 29 µg/day
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