Carmel Coloring in Soda May Contain Potential Carcinogen

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The dark-brown coloring of many soft drinks contains a chemical that Consumer Reports warns may contain a potential carcinogen.

Glass cola

On January 23rd, Consumer Reports published findings showing that many dark colored soft drinks contain the chemical 4-methylimidazole (4-MeI). In the United States, product labels refer to the chemical as “caramel coloring,” and although that sounds good it actually has nothing to do with real carmel.

In 2007, a study concluded that 4-MeI caused cancer in mice [1]. Three years later in 2010, the International Agency for Research on Cancer determined the 4-MeI to be “possibly carcinogenic to humans” [2]. Although there’s no federal limit for levels of 4-MeI in foods and beverages, since January 2012 the state of California requires manufacturers to label a product sold in the state with a cancer warning if it exposes consumers to more than 29 micrograms of 4-MeI per day.

Consumer Reports tested 81 cans and bottles of various popular brands of soft drinks from stores in California and New York between April and September 2013. If the brand tested above 29 micrograms, it was tested again from the same areas in December 2013.

Both rounds of testing found that the level of 4-MeI in the samples of Pepsi One and Malta Goya purchased from both locations exceeded 29 micrograms per can or bottle:

  • California Pepsi One average: 41.5 micrograms
  • New York Pepsi One average: 178.05 micrograms
  • California Malta Goya average: 334.3 micrograms
  • New York Malta Goya average: 325.1 micrograms

In testing, three brands — Coke, Diet Coke and Coke Zero — came in under 5 micrograms per can. Sprite, which was tested as a control (since it’s a clear soda), showed no significant levels of 4-MeI.

Consumer Reports is petitioning the Food and Drug Administration (FDA) to set a federal standard for 4-MeI. In a statement, the FDA said it does not believe that 4-MeI from caramel coloring at levels currently in food pose a risk. The FDA are currently doing their own tests of foods, including sodas, for 4-MeI. In addition, they are reviewing new safety data on 4-MeI to determine what, if any, regulatory action needs to be taken.

Source: Consumer Reports


  1. National Toxicity Program. Toxicology and carcinogenesis studies of 4-methylimidazole (Cas No. 822-36-6) in F344/N rats and B6C3F1 mice (feed studies). Natl Toxicol Program Tech Rep Ser. 2007 Jan;(535):1-274.
    View abstract
  2. IARC Monograph on 4-methylimidazole. International Agency for Research on Cancer. 2010 Dec 27.
About the Author

Jenny Jessen is a senior writer at Highlight HEALTH.