Dietary heterocyclic amines and human cancer risk

Sammanfattning: Heterocyclic amines formed in meat during cooking are multi-site animal carcinogens and form DNA adducts in human tissues, but their relevance to human carcinogenesis has yet to be determined. The aim of this thesis was to investigate, by epidemiological methods, whether heterocyclic amines are responsible for part of the diet-related cancer burden in humans. Frequently eaten fried meat dishes in an elderly population in Stockholm, Sweden, were identified, and we found meat to be eaten, on the average, 1.4 times per day, and frying to be the most popular cooking method. Altogether, 22 frequently consumed dishes were fried/baked in a standardized manner under controlled conditions at 150, 175, 200, and 225°C, and the content of heterocyclic amines, including IQ, MelQ, MelQx, DiMelQx, and PhlP, was determined. The formation of heterocyclic amines was found to be temperature-related and the highest amounts were detected in minute steak, pork filet, and bacon fried at 225°C. A method to assess the individual intake of heterocyclic amines in an epidemiological context was developed by linking values for heterocyclic amines obtained from chemical analyses to food consumption data collected by means of a semiquantitativc food frequency questionnaire comprising 188 food items. Variables used to assess the intake of heterocyclic amines were intake frequency, type of dish, cooking method, portion size, degree of surface browning of the meat, and intake of gravy. When the number or dishes in the food frequency module was reduced from 39 to 15 dishes, based on the most informative dishcs according to the total intake or the between-person variancc, only a limited amount of misclassification was introduced. The total daily intake of IQ, MelQ, MelQx, DiMelQx, and PhlP among controls ranged from zero to 1816 ng, with a median of 77 ng. Relative risks of cancer were estimated in a population-based case-control study in Stockholm, and information was retrieved from 553 controls, 352 cases of colon cancer, 249 rectal cancer cases, 273 bladder cancer cases, and 138 cases of kidney cancer. The study disentangles the effect of meat from the effect of heterocyclic amines, and we found that an intake of heterocyclic amines within the usual dietary range in the study base is unlikely to increase the incidence of cancer of the colon, rectum, bladder, or kidney. However, for intakes above 1900 ng/day, our data are consistent with the possibility of human carcinogenicity, but the precision is extremely low. Keywords: cancer, colon, rectum, bladder, kidney, human, heterocyclic amines, meat ISBN 91-628-2884-3