Heterocyclic amines are mutagenic and carcinogenic compounds that are formed in cooked and charred foods.12 They form particularly in meat and fish even if cooked at relatively low temperatures.13 In fact, it is estimated that the average consumption of these compounds is as high as 100µg per person per day,14 but other calculations place daily consumption in the range of 0.4 to 16 µg/day.2 Heterocyclic amines have been found to elicit carcinogenicity in the liver, lung, oral cavity, stomach and intestines of rats and mice, and have also been implicated in cancer of the lymphatic systems, blood vessels, skin and mammary glands. Over 20 mutagenic heterocyclic amines have been isolated from cooked animal products, and well done portions of meat contain higher concentrations than medium or rare portions. To obtain these compounds for experimental purposes, a standard protocol of grilling or frying for 6 min. at 200°C is used. Generally, frying, grilling and barbequing produce more of these compounds than does stewing, steaming, microwaving or poaching.2
The chemical structures of these compounds and the concentrations found in some foods are presented in figure 4.7 and table 4.2.
Heterocyclic amines are relevant carcinogens in humans, but in the case of colon cancer their relative contribution may be small (0.25% of all colon cancers).2 Food that will be particularly suspect in terms of heterocyclic amines will be cured and baked or fried meats. Even beer, soybeans, protein isolates and fried mushrooms were found to contribute significantly to the daily intake of these compounds. A study of heterocyclic amine formation in swine meat heated to 200°C showed that the main reactants of the mutagen-forming reactions are amino acids and creatine.15