Dark-Colored Sodas May Have Toxic Backwash, Or Not

The Center for Science in the Public Interest (CSPI) has made a claim that “caramel coloring” used to improve the eye appeal of colas and other dark-colored soft drinks contains the carcinogenic by-products 2-methylimidazole and 4-methylimidazole (shown) and thus might be a cause of thousands of cancers in the U.S. The nonprofit consumer advocacy organization made its announcement via a regulatory petition filed with the Food & Drug Administration on Feb. 16.


Besides being used in colas, the artificial coloring, which can range from yellowish to black, is used in some baked goods, precooked meats, soy and Worcestershire sauces, chocolate-flavored products, and even whiskey and beer. It’s typically made by pyrolyzing sugar with the aid of ammonium and/or sulfite compounds, a process that forms many derivative chemicals. This browning process is similar to, but distinct from, the Maillard reaction between a sugar and an amino acid. CSPI wants FDA to revoke regulations allowing the types of caramel coloring made using ammonium compounds, which contain the imidazoles. “Carcinogenic colorings have no place in the food supply, especially considering that their only function is a cosmetic one,” CSPI Executive Director Michael F. Jacobson said when announcing the petition. CSPI is invoking the Delaney Clause, an amendment to the Food, Drugs, & Cosmetic Act of 1938, to state that FDA is obligated to ban caramel coloring--the clause stipulates that FDA “shall not approve for use in food any chemical additive found to induce cancer in man, or, after tests, found to induce cancer in animals.” The issue of the toxicity or nontoxicity and possible regulatory control of the imidazole compounds has been bouncing around for a few years. CSPI based its petition on a pair of 2007 studies (1 and 2) published by the National Toxicology Program (NTP), a unit of the National Institute of Environmental Health Sciences. The studies conclude that 2- and 4-methylimidazole, compounds known to be in cigarette smoke, caused cancer in rats and mice. But NTP has not listed the imidazole compounds as being carcinogenic. CSPI also cites a paper by researchers at the University of California, Davis, who detected 4-methylimidazole in five brands of cola. The UC Davis researchers extrapolated their data to the NTP studies and concluded that “the amounts ingested from these beverages may not be significant.” Nonetheless, CSPI’s press announcement suggests that the amount of the compound in colas is large enough to be cause for concern, although the amount in soy sauce and other products is likely small enough to not be a problem. Caramel coloring is largely unregulated in the U.S., but California state health officials have added 4-methylimidazole to the state’s list of “chemicals known to the state to cause cancer.” And under California’s Proposition 65, foods or other products containing certain levels of cancer-causing chemicals must carry warning labels. For 4-methylimidazole, that level is 16 µg per person per day. Popular brands of cola contain about 200 µg of 4-methylimidazole per 20-ounce bottle, which CSPI cites from the UC Davis study. If California’s regulation is finalized, Coke, Pepsi, and other soft drinks would be required to bear a cancer warning label. Since its inception in 1971, CSPI has had success changing labeling requirements or limiting the use of several chemicals, including Violet No. 1 coloring, sodium nitrite and sodium nitrate, sulfites, partially hydrogenated vegetable oils, and salt. It seems like caramel coloring might join this list. But in responding to CSPI’s petition, Coca-Cola issued a statement that in part says:

Credit: Coca-Cola

“CSPI’s statement irresponsibly insinuates that the caramel used in our beverages is unsafe and maliciously raises cancer concerns among consumers. This does a disservice to the very public for which CSPI purports to serve. In fact, studies show that the caramel we use does not cause cancer. Further, the caramel we use does not contain [2-methylimidazole] alleged by CSPI. “[4-Methylimidazole] is found in trace amounts in a wide variety of foods and beverages, including Coca-Cola. In fact, it forms normally in the ‘browning reaction’ while cooking, even in one’s own kitchen.          “These extrapolations by CSPI to human health and cancer are totally unfounded.  We have a responsibility to challenge Mr. Jacobson’s statements and make the truth clear for the public.” Separately, the American Beverage Association added: “No health regulatory agency around the globe, including the Food & Drug Administration, has said that [4-methylimidazole] is a human carcinogen. This petition is nothing more than another attempt to scare consumers by an advocacy group long-dedicated to attacking the food and beverage industry.” … “In fact, a group of plaintiffs--the California League of Food Processors, American Beverage Association, Grocery Manufacturers Association, and National Coffee Association--has filed a lawsuit against the California Office of Environmental Health Hazard Assessment for its wrongful listing of [4-methylimidazole] under Proposition 65. … “The bottom line is that this petition to the FDA by a group of activists is not based on sound science and is unnecessarily raising the fears of consumers.” As for FDA’s part, public affairs officer Patricia El-Hinnawy tells Newscripts that “FDA will carefully review the petition as well as any new data bearing on the safety of 2-methylimidazole and 4-methylimidazole. In the interim, based on all current science, FDA assesses that risk, if any, from the by-products would be associated with long-term exposure. FDA has no reason to believe that there is any immediate or short-term danger presented by the substances in food.” Stay tuned.

Author: Steve Ritter

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  2. Hi) Is it possible to provide a link or proper citation to the studies that is done by NTP ( because they does not seems working)

  3. Thanks, Steve. Keep up the great work!