When Ira Glass of public radio's "This American Life" recently broadcast what he believes to be the original recipe for Coca-Cola, one of the ingredients was caramel.

As the recipe has been modified over the years, the soda now gets its caramel color from a mixture containing compound 4-methylimidazole, also known as 4-MI or 4-MEI. It's used in other colas, too, such as Pepsi. But the Center for Science in the Public Interest says it's a known carcinogen and has no place in our food supply.

Now that the CSPI has petitioned the U.S. Food and Drug Administration to ban it, and California has added the compound to its list of known carcinogens, Coca-Cola says it will switch to a new formulation — allowing the company to avoid cancer warning labels on cans in California.

"The company did make the decision to ask its caramel suppliers to make the necessary manufacturing process modifications to meet the requirement of the State of California," Diana Garza Ciarlante, a Coca-Cola spokeswoman, told National Public Radio, adding that its coloring has always been safe.

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"The fact is that the body of science about 4-MEI in foods or beverages does not support the erroneous allegations that CSPI would like the public to believe," she said.

The FDA says people would have to drink more than 1,000 cans of soda a day to cause any concern.

CSPI doesn't agree.

"Carcinogenic colorings have no place in the food supply, especially considering that their only function is a cosmetic one,” Michael Jacobson, CSPI's executive director, said in a press release.

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The group also says the label is misleading.

"Most people would interpret ‘caramel coloring’ to mean ‘colored with caramel,’ but this particular ingredient has little in common with ordinary caramel or caramel candy,” Jacobson said. “It’s a concentrated dark brown mixture of chemicals that simply does not occur in nature. Regular caramel isn’t healthful, but at least it is not tainted with carcinogens.”

The supplier says it modified the color by changing the manufacturing process to reduce the levels of 4-MI, altering the temperature, pressure and ingredients.

Will consumers notice the difference? Not at all, Coke says.