Cooked food contains a variety of mutagenic heterocyclic
amines. All the mutagenic heterocyclic
amines tested were carcinogenic in rodents when given in the diet at 0.01-0.08%. Most of them induced
cancer in the liver and in other organs. It is noteworthy that the most abundant heterocyclic
amine in cooked food, 2-amino-1-methyl-6-phenylimidazo[4,5-
b]pyridine, produced colon and mammary
carcinomas in rats and
lymphomas in mice but no
hepatomas in either. 2-Amino-3-methylimidazo[4,5-f]
quinoline induced
liver cancer in monkeys. Formation of adducts with
guanine by heterocyclic
amines is presumably involved in their
carcinogenesis. Quantification of heterocyclic
amines in cooked foods and in human urine indicated that humans are continuously exposed to low levels of them in the diet. These low levels of heterocyclic
amines are probably insufficient to produce human
cancers by themselves. However, a linear relationship between
DNA adduct levels and a wide range of doses of a heterocyclic
amine was demonstrated in animals. It suggests that even very low doses of heterocyclic
amines form
DNA adducts and may be implicated in the development of human
cancer under conditions in which many other
mutagens-
carcinogens,
tumor promoters, and factors stimulating
cancer progression exist.