Cancerous Colas? A closer look at the 4-Methylimidazole (4-MEI) controversy

We already know there’s nothing healthful about drinking colas. But did you know that the cola ingredient 4-Methylimidazole, aka 4-MEI, is considered by Consumer Reports as well as the state of California, to be a carcinogen? Yes, it may cause cancer. 4-MEI is a product of roasting and thus is naturally found in roasted coffee and soy sauce (though generally at safe levels). More importantly, however, it is produced in the chemical process used to make caramel coloring types 3 and 4. The very caramel colorings used in your favorite colas, including Coca Cola and Pepsi.

Where’s the evidence? In short, a 2007 National Toxicology Program study found that mice that consumed 4-MEI developed lung cancer. Consumer Reports then presented a teleconference in which they discussed the above study and the resultant California guidelines set by Prop 65 defining safe levels of 4-MEI. California defines “safe” as 29 micro-grams per day. How did they choose that level? They used a commonly-accepted level of cancer risk: 1 in 100,000. That means that for every 100,000 people who ingest 29 micro-grams of MEI every day for a lifetime, one person will develop cancer from it. Consumer Reports says this is not acceptable. They note that prior to this study, the acceptable cancer risk for such chemicals has been 1 in 1 million, not 1 in 100,000. Furthermore, they recommend higher precaution with this chemical since no clear mechanism of cancer has been established.

Consumer Reports also conducted its own studies and looked at several colas and their levels of 4-MEI. Some colas were found to have up to 100 times the limit set by California’s Prop 65 limit. Thus, if 4-MEI can cause cancer, there are colas out there that should concern us.

In addition, Consumer Reports made some straightforward points: 1) The current standard of 29 micrograms per day is too high; and 2) The process by which caramel colors are made can be altered such that 4-MEI levels are dramatically reduced.

A Little More Detail…What’s 4-MEI?

From a California government fact sheet on 4-MEI:
4-Methylimidazole (4-MEI) is a compound used to make certain pharmaceuticals, photographic chemicals, dyes and pigments, cleaning and agricultural chemicals, and rubber products.

4-MEI is formed during the production of certain caramel coloring agents used in many food and drink products. It may also be formed during the cooking, roasting, or other processing of some foods and beverages.

Most people are exposed to 4-MEI by consuming foods and beverages that contain it. Products that potentially contain 4-MEI include certain colas, beers, soy sauces, breads, coffee, and other products.

Workers may also be exposed to 4-MEI if they manufacture certain pharmaceuticals, dyes, and rubber, or if they work with ammoniated livestock feed.

4-MEI was added to California’s Proposition 65 list of carcinogens due to the study published in 2007 by the federal government’s National Toxicology Program that showed increases in lung cancer among male and female mice consuming 4-MEI over a long period. (Chan et al., 2008) The U.S. Food & Drug is currently reviewing the potential cancer risks from 4-MEI. (Chan et al., 2008)

Counter Argument
BUT… a study published in 2011 found that 4-MEI actually decreased the incidence of cancer in rats! “The number and magnitude of the observed decreases in tumor incidences associated with 4-MEI exposure in rats are compelling and extraordinary”. (Murray, 2011) HOWEVER…there is a very large conflict of interest here: “the author received funding from the American Beverage Association”. (Murray, 2011)

So Now What?
Can 4-MEI cause cancer? Yes, in mice. Can it reduce the risk of cancer? Yes, in rats. What then of humans? As mentioned in the Murray article, “it is unclear whether humans are more like mice or rats in terms of their response to 4-MEI”. This is the key point here, and additional research is certainly needed. Perhaps a long-term study (cohort) of high 4-MEI consumers, or epidemiological data linking human cancers with consumption of high 4-MEI foods, is needed.

Protecting yourself
What should the average consumer do? What recommendations can be gleaned from this research and the conflicting findings between the scientific and beverage communities?

Our opinion is: why risk it? 4MEI has been found to cause cancer in animals. We humans are animals. We share many of the same biochemical pathways with our rodent friends. The burden of proof is on the manufacturers, and they should demonstrate that a chemical additive is not detrimental to human health before they put it in food products.

Another reason to not drink Cola
At the end of the day, this is another reason to not drink cola. It has no nutritional content and contributes to our ever-expanding global obesity epidemic. When in doubt, ask yourself who benefits from this controversy. On the one side you have public interest groups and federal/state agencies, who generally are not looking to create concern over such a popular dietary item. On the other you have multi-million dollar corporations that stand to loose millions…whose argument do you trust?

Links, references and resources
This post was written by Martin Aramburu, UIC Medical Student. Edited by Dr. Susan Buchanan.


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