Sulphite ammonia caramel
The dark caramel colour used in cola and many brown foods. Its by-product 4-MEI is classed as possibly carcinogenic, so the amount in the colour is capped.
4-MEI, a by-product formed when this colour is made. It is classed possibly carcinogenic (animal lung tumours). The colour itself is the carrier; the by-product is the flagged part.
What is it?
A dark brown food colour made by heating sugars with both ammonium and sulphite compounds. It is one of four caramel colour classes and is the type used in cola.
What does it do?
Colours food and drink a deep brown and gives cola and similar drinks their characteristic colour.
Where you will see it
Colas and many soft drinks, soy sauce, dark beers and some whiskies, gravies, sauces, vinegars and confectionery. On a UK label it reads as E150d or 'colour: sulphite ammonia caramel' / 'caramel colour'.
What the science says
4-MEI by-product
Making class III and IV caramel colours creates 4-methylimidazole (4-MEI) as an unintended by-product of the browning reaction. IARC classed 4-MEI as Group 2B, possibly carcinogenic to humans, based on lung tumours in mice (not seen in rats). EU rules cap how much 4-MEI E150d may contain, and EFSA judged that the highest realistic intake of 4-MEI from E150c and E150d did not raise a concern at the levels it assessed.
4-MEI is classified Group 2B, possibly carcinogenic to humans, based on lung tumours in mice.
4-MEI is formed as an unintended by-product during manufacture of class III and IV caramel colours.
A study of commercial products found 4-MEI in class IV caramel colours ranging from 112 to 1276 mg/kg.
Genotoxicity tests (Ames, micronucleus) for 4-MEI were negative, supporting a non-genotoxic mode of action.
California Prop 65 and cola exposure
California lists 4-MEI under Proposition 65 as a chemical known to cause cancer. A Prop 65 warning is required only when daily exposure exceeds the no-significant-risk level of 29 micrograms of 4-MEI per day. Testing found a 12oz can of cola could contain roughly 130 micrograms of 4-MEI, well above that threshold, which led several makers to reformulate their caramel colour to lower 4-MEI and stay below the warning level.
OEHHA set the no-significant-risk level for 4-MEI at 29 micrograms per day, effective February 2012; a Prop 65 warning is required only above this level.
A 12oz can of cola was found to contain about 130 micrograms of 4-MEI.
EFSA re-evaluation
EFSA re-evaluated all four caramel colours in 2011 and set a group acceptable daily intake of 300mg/kg body weight/day, with a tighter ADI of 100mg/kg for E150c. It did not find the caramel colours themselves to be genotoxic or carcinogenic, and concluded the highest realistic 4-MEI exposure from E150c and E150d did not give rise to concern at the levels assessed. It recommended EU specifications be updated to cap by-products of toxicological interest.
EFSA established a group ADI of 300mg/kg bw/day for caramel colours E150a-d, with a more restrictive 100mg/kg bw/day for E150c.
EFSA concluded the highest exposure to 4-MEI from E150c and E150d did not give rise to concern at the levels assessed.
Where it stands with the regulators
Who should be careful
Anyone avoiding sulphites should note the sulphite-process origin, though the finished colour is not a declared allergen. If you want to limit 4-MEI exposure, the main dietary source is regular cola and other heavily caramel-coloured drinks; check labels for E150d or 'caramel colour' and moderate intake.
The honest read
The flagged issue is the by-product 4-MEI, not the caramel colour acting as sugar. 4-MEI is classed possibly carcinogenic on the strength of animal lung tumours, and California requires a Prop 65 warning only when daily 4-MEI intake tops 29 micrograms. A can of cola can sit above that, which is why many makers cut their 4-MEI. The colour itself was not found genotoxic by EFSA; the open question is the by-product and how much of it you take in from regular cola drinking.
Related additives
Common questions
Is E150d banned in the UK?
No. E150d is authorised as a food colour in Great Britain under assimilated Regulation (EC) No 1333/2008, with a specification limit on its 4-MEI by-product.
Is the caramel colour in cola carcinogenic?
The caramel colour itself was not found carcinogenic by EFSA. Its by-product 4-MEI is classed by IARC as Group 2B, possibly carcinogenic to humans, based on lung tumours in mice. California requires a cancer warning only when 4-MEI intake exceeds 29 micrograms a day, a level a can of cola can exceed.
What foods contain E150d?
Colas and many soft drinks, soy sauce, dark beers and some whiskies, gravies, sauces, vinegars and confectionery. It appears on labels as E150d or 'caramel colour'.
Is E150d vegan?
E150d is made from sugars heated with ammonium and sulphite compounds, with no animal-derived ingredients, so it is plant-based. Confirm the finished product if strict, as cross-use varies by manufacturer.
Sources
- IARC Monograph 101 - 4-Methylimidazole (Group 2B)
- CA OEHHA Prop 65 - No Significant Risk Level for 4-MEI (29 microgram/day findings)
- EFSA - Scientific Opinion on the re-evaluation of caramel colours (E150a,b,c,d), 2011
- UK FSA regulated-products - Sulphite ammonia caramel (E150d)
- Commission Regulation (EU) No 231/2012 - additive specifications
- Caramel Color in Soft Drinks and Exposure to 4-MEI: A Quantitative Risk Assessment (PLOS One)
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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