A nonprofit group is calling for the US Food and Drug Administration (FDA) to ban artificial caramel coloring used in Coca-Cola, Pepsi and other foods because animal tests suggest the additive is contaminated with two cancer-causing chemicals.

The Center for Science in the Public Interest (CSPI) filed a regulatory petition to the FDA on Wednesday, asking for them to ban the use of the artificial brown coloring, which contains two chemicals, 2-methylimidazole and 4-methylimidazole (2-MI and 4-MI also referred to as 2-MEI and 4-MEI), that government-led studies have shown caused liver, lung, leukemia, and thyroid cancer in lab mice and rats.

CSPI executive director Dr Michael F Jacobson told the media that:

“Carcinogenic colorings have no place in the food supply, especially considering that their only function is a cosmetic one.”

He urged the FDA to “act quickly to revoke its approval of caramel colorings made with ammonia”.

The CSPI say the artificial caramel coloring used in the beverage and food industry is “quite different to real caramel” and is not made in the same way as one might make it at home, by melting sugar in a saucepan.

They say manufacturers make the artificial brown coloring by reacting sugars with ammonia and sulfites under high temperature and pressure, and this leads to the formation of the two chemicals.

The current federal regulations allow four types of caramel coloring: two of which are made with ammonia. It is these two that the CSPI want the FDA to ban. One is known as Caramel III and the other as Caramel IV.

Caramel III is made with ammonia but not sulfites, this is used to color beer, soy sauce, and other foods. Caramel IV is made with ammonia and sulfites and is used to color colas and other dark soft drinks.

To make their case the CSPI say chemicals that cause cancer in animals are considered to be potentially carcinogenic to humans and cite animal studies conducted by the National Toxicology Program, a division of the National Institute of Environmental Health Sciences, that showed there is “clear evidence” that 2-MI and 4-MI cause cancer in animals.

They say researchers at the University of California, Davis, found significant levels of 4-MI in five brands of cola.

Some of the scientists who worked at the National Toxicology Program are among the five experts on causes of cancer in animals who have joined with the CSPI on calling for the FDA to ban the use of artificial caramel made with ammonia.

They wrote a letter to Dr Margaret Hamburg Commissioner for Food and Drugs, in which they said:

“The American public should not be exposed to any cancer risk whatsoever as a result of consuming such chemicals, especially when they serve a non-essential, cosmetic purpose.”

The CSPI also argues that the phrase “caramel coloring” is misleading when used to describe those made with ammonia or sulfite, and manufacturers should not be allowed to label products that contain them as “natural”. They maintain it would be more accurate to use phrases like “ammonia process caramel” or “ammonia sulfite process caramel”.

Jacobson said most people would think “caramel coloring” meant “colored with caramel”, but this ingredient is nothing like ordinary caramel as in caramel candy, it’s “a concentrated dark brown mixture of chemicals that simply does not occur in nature”.

He said even though regular caramel isn’t good for your health, “at least it is not tainted with carcinogens”.

The CSPI points out that California has added 4-MI to its list of “chemicals known to cause cancer”, which means, because of California’s Proposition 65 regulation, food or other products that have above a certain level of these carcinogens must carry warning labels. In California the threshold for 4-MI is 16 micrograms per person per day from an individual product.

But popular makes of cola have about 200 micrograms of 4-MI per 20-ounce (0.6 litres) bottle, say the CSPI, which is less than many people consume every day, especially adolescent boys. If California finalizes this legislation, then Coke, Pepsi, and other soft drinks would have to carry labels saying they contain chemicals that can cause cancer.

The CSPI initiative has provoked a strong reaction from manufacturers.

The American Beverage Association (ABA) say it is an “outrageous and egregious attempt to dupe and scare the public”, from a group that “makes its living bashing the food and beverage industry”.

They told the press that the CSPI petition “is not based on sound science and is unnecessarily raising the fears of consumers”.

They accuse the CSPI of conducting a “science-by-press-release” campaign to scare the public into thinking caramel coloring is harmful because of 4-MI, a byproduct of heating, roasting and cooking that they say is found in a wide variety of foods and drinks, from baked goods like breads and cakes to molasses and coffee.

The ABA says caramel color is not a threat to human health “even when it contains minute amounts of 4-MEI [4MI]”, and that studies have confirmed this and the FDA has classed caramel color as generally recognized as safe, as have many regulatory bodies worldwide.

The ABA say even the National Toxicology Program (NTP), which the CSPI has cited in order to make its case, has not classed 4-MI as a cancer causing agent, not even as “reasonably anticipated to be a human carcinogen”.

They told the press that the former director of the Toxicology Research and Testing Program, Dr Ernest McConnell, wrote that “4-MEI [4MI] does not have sufficient evidence of carcinogenicity to be placed on the list”.

They appealed to consumers to use their common sense, and ask whether it is plausible that an industry with companies that have been in business for more than 100 years would ever “put the safety of their consumers at risk”.

Caramel coloring is one of several artificial food colorings that the CSPI is asking the FDA to ban. The others include Yellow 5 and Red 40, which are thought to cause behavioral problems like ADHD in children, and Red 3 and Yellows 5 and 6, which, according to the CSPI, also pose cancer risks.

The FDA Food Advisory Committee is due to review the issue at the end of March.

Sources: CSPI, ABA (press releases, 16 Feb 2011).

Written by: Catharine Paddock, PhD