Are the “carcinogenic” chemicals that are produced when foods are cooked really cause for concern?
Cooking food is the major process adopted to produce flavor chemicals, which give foods a characteristic desirable roasted or toasted flavor. More than 1,000 low molecular weight compounds are known to be produced once a food is heated, and the number of known compounds is increasing steadily. The amounts of these chemicals formed are generally in very trace levels (around the level of µg/kg of food or parts per billion, ppb), but for most of these compounds, detailed information about possible toxicity at this level is not yet established.
One of these compounds is 4-Methylimidazole (4-MEI), which forms from a reaction between amino acids or proteins and sugars, carbohydrates, or lipids when exposed to heat. This past March, an independent study commissioned by the consumer interest group Center for Science in the Public Interest (CSPI) found that four of the best-selling sodas (Coca-Cola, Diet Coke, Pepsi and Diet Pepsi), which use caramel color produced by heating sugar and ammonia, contain potentially unsafe levels of 4-MEI, which according to the report had recently been linked to cancer. “The average amount (138 μg) of [4-MEI] that out rests found in a 12-ounce can of [cola] is 4.8 times greater than California’s 29 μg-per-day limit, indicating a lifetime risk of cancer of 5 out of 100,000 people,” CSPI Executive Director Michael Jacobson wrote in a letter to the US Food and Drug Administration that described the results of the study. This has caused a stir in the consumer research community, with many advocating for the reduction or elimination of 4-MEI from marketed food and drinks.
But I do not believe 4-MEI is harmful at the levels found in these products. Stating that these sodas contain potentially unsafe levels of the chemical is misleading—it is present only trace levels. Furthermore, the supposed cancer link stems solely from a handful of animal experiments; there is currently no evidence of a link between 4-MEI and disease in humans.
I recently conducted a study that demonstrated that adding sulfite, which is one of the most commonly used caramel ingredients, reduces 4-MEI formation. But when we try to reduce 4-MEI, we may have to remove a tremendous number of other desirable chemicals formed in foods by heat treatment. Furthermore, it is important to keep in mind that heat treatment of foods does more than give the food palatable flavors, colors, and textures; heat treatment also kills harmful microorganisms, and it should be stressed that ingesting such microorganisms may cause more toxic effect to humans than ingesting trace levels of 4-MEI.