Consuming Sodas Daily Increases Cancer Risk

An ingredient in soda, 4-methylimidazole, is a potential carcinogen and people who drink one or more can of soda per day could be exposed to it, increasing their risk of cancer.

Public health researchers have analyzed soda consumption data in order to characterize people's exposure to a potentially carcinogenic byproduct of some types of caramel color. Caramel color is a common ingredient in colas and other dark soft drinks. The results show that between 44 and 58 percent of people over the age of six typically have at least one can of soda per day, possibly more, potentially exposing them to 4-methylimidazole (4-MEI), a possible human carcinogen formed during the manufacture of some kinds of caramel color.

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Building on an analysis of 4-MEI concentrations in 11 different soft drinks first published by Consumer Reports in 2014, researchers led by a team at the Johns Hopkins Center for a Livable Future (CLF) estimated exposure to 4-MEI from caramel-colored soft drinks and modeled the potential cancer burden related to routine soft drink consumption levels in the United States.

Senior author of the study Keeve Nachman, PhD, said that soft drink consumers are being exposed to an avoidable and unnecessary cancer risk from an ingredient that is being added to these beverages simply for aesthetic purposes. This unnecessary exposure poses a threat to public health and raises questions about the continued use of caramel coloring in soda.

While the 2014 study of the 110 samples of soda brands was not large enough to recommend one brand over another or draw conclusions about specific brands, results indicated that levels of 4-MEI could vary substantially across samples, even for the same type of beverage. "For example, for diet colas, certain samples had higher or more variable levels of the compound, while other samples had very low concentrations," says Tyler Smith, lead author of the study and a program officer with the CLF.

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While there's currently no federal limit for 4-MEI in food or beverages, Consumer Reports petitioned the Food and Drug Administration to set limits for the potential carcinogen last year. It also shared the findings with the California Attorney General's office, which enforces the state's Proposition 65 law aimed at reducing consumers' exposure to toxic chemicals. Under this state law, any food or beverage sold in the state that exposes consumers to more than a specific amount of 4-MEI per day requires a health-warning label.

The results are published online in PLOS One.