The associations between methods of cooking meats and colorectal cancer were examined in a population-based case-referent study performed in Stockholm in 1986-1988. The study included 559 cases and 505 referents. Total meat intake, frequent consumption of brown gravy, and a preference for a heavily browned meat surface each independently increased the risk for colorectal cancer. The relative risks (RR) were higher for rectal than for colon cancer, and for boiled meat (RR colon = 1.7, RR rectum = 2.7) than for meat fried with a medium or lightly browned surface (RR colon = 0.8, RR rectum = 1.1), but the highest risks were for meat fried with a heavily browned surface (RR colon = 2.8, RR rectum = 6.0). The analyses were adjusted for year of birth, gender and fat intake. Further adjustments for total energy, dietary fiber intake, body mass and physical activity had little or no influence on the results. The findings suggest that, in addition to frequent meat intake, a heavily browned meat surface formed when frying meat at high temperatures is important in the etiology of colorectal cancer.

Lactic acid bacteria have been reported to have antimutagenic properties in ,+fro. In order to investigate whether Lactobacillus acidophilus supplements have antimutagenic effects in humans, 1 1 healthy subjects on a standardised diet consumed fried beef patties twice daily for 3 d. The diets were supplemented with ordinary Lmtococcus fermented milk (phase 1) and thereafter with L . ucidophilus fermented milk (phase 2), whereby the excretion of mutagenic activity was determined in urine and faeces. In both faeces and urine high levels of mutagenicity were detected during phase 1. There was an increase in lactobacilli in the intestinal microflora in seven of I 1 subjects by the L. ucidophilus supplement (phase 2), and the mutagenic activity in urine was 72 per cent lower on day 2 (P< 0.01) and 55 per cent lower on day 3 (P< 0.05) compared to days 2 and 3 in phase 1. The total faecal and urinary mutagen excrction on day 3 during phase 2 was 47 per cent lower compared to day 3, phase 1 (P

Creatine or one of 15 amino acids were mixed with minced pork before broiling at 200 degrees C. Total mutagenic activity and reversed-phase HPLC-separated mutagenicity profiles were determined for the crust and pan residue of all samples and also in the aerosol fraction of the smoke formed during cooking of the creatine-fortified samples. Addition of 5% (w/w) creatine increased the total mutagenicity 4-fold without changing the mutagenicity profile of either crust, pan residue or aerosol. Amino acid addition (1% w/w) increased the total mutagenicity between 1.5 (lysine) and 43 times (threonine). In most cases the mutagenicity profiles of crust and pan residues were changed by amino acid addition. Dry-heated mixtures of amino acids and creatine were all mutagenic with a 250-fold range between the amino acids. The production of known food mutagens in these mixtures was analyzed by LC-MS of HPLC-fractionated mutagenic peaks. Serine, threonine, phenylalanine, alanine, leucine and tyrosine were all shown to give rise to one of the known food mutagens 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) or 2-amino-trimethylimidazopyridine (TMIP). Lyophilized and subsequently fried meat patties and a heated powder of lyophilized meat juice were both mutagenic, with mutagenicity profiles similar to the regular meat crust, showing that water is not a prerequisite for mutagen formation in meat. MeIQx, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-di-MeIQx) and PhIP were shown, by LC-MS, to be present in the dry-heated meat juice. It is concluded that creatine and free amino acids are the main reactants of the mutagen-forming reactions that occur during frying of meat. Creatine is probably a necessary part of all of these reactions; what specific compounds are formed in each case therefore depends upon the levels in the meat of certain free amino acids and their interactions with other, as yet unknown, compounds in the meat.

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