 Used as a coloring agent in products ranging from colas and beer to gravies and soy sauce, carmel coloring may be the world's most widely consumed food coloring, helping to sell over a billion servings a day. Unfortunately, the manufacture of certain artificial carmel coloring can lead to the formation of carcinogens, such as formethylamidazole, which causes cancer in mice, but not rats, or at least not male rats, it's unclear whether humans are more like mice or rats in terms of their response to the carcinogen. To be safe, California officially listed it as a carcinogen and started requiring warning labels on soft drinks containing more than 29 micrograms per can. The soft drink industry was unsuccessful in opposing the action, so were forced to reduce carcinogen levels in their products, but only in California. Buy Coke anywhere else and may have up to five times the limit. Remember Coca-Cola's tab clear, though, or crystal Pepsi? Clearly, they can do away with carcinogenic colorings altogether.