Heterocyclic aromatic amine content in pre-processed meat cuts produced in Canada.

In an ongoing survey, the presence of heterocyclic aromatic amines (HAAs) was determined in processed, ready-to-eat meat products sold as 'meat cuts'. HAAs are a group of recently recognized mutagenic/carcinogenic contaminants in foods that are produced during the heat processing of meat. 16 samples of meat cuts (e.g. turkey breast, salami, chicken loaf, cooked ham, all beef meat, pepperoni, etc.), randomly purchased from supermarkets and specialty food stores in the Ottawa area, were analysed for the presence of eight HAAs. The isolation of HAAs was based on sequential liquid-liquid extraction procedures of the samples at both acidic and basic pH values. The mutagenic activity of these samples was determined using the Ames/Salmonella microsome assay with the strain TA98 plus rat liver S-9 metabolic activation. The mutagenicity of these samples ranged from undetectable to slightly active. The highest mutagenic activity, 141 induced revertants/g, was found in a smoked turkey breast sample. 11 samples were not mutagenic, including two that indicated a tendency for inhibition of the spontaneous revertants. The remaining four samples exhibited very low mutagenic activity. For chemical analysis, the extracts were purified with two solid phase extraction cartridges. Quantitative analysis was performed by using liquid chromatography for separation and mass spectrometry for detection. With the exception of trace amounts (0.4 ng/g) of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in the sample with highest mutagenic activity, the chemical analysis did not detect the presence of any of the eight most frequently found HAAs in fried or broiled meat products. These data suggest that consumption of meat cuts does not present a serious health risk from HAA-type contaminants.

The effect of teas on the in vitro mutagenic potential of heterocyclic aromatic amines.

Water extracts of eight brands (five types: 'green', 'black', 'oolong', decaffeinated and instant) of common teas (derived from Camellia sinensis) and infusions of six randomly selected herbal teas were examined for inhibitory or potentiating effects on the mutagenicity of eight heterocyclic aromatic amines (HAA) using the Ames Salmonella typhimurium TA98 and S-9 assay. HAA, produced in foods during regular heat processing of meat, exhibit mutagenic/carcinogenic activities. Tea extracts from C. sinensis displayed very potent antimutagenic effects against most HAA: total or substantial inhibition of mutagenic activity of the eight HAA was obtained with extracts equivalent to 50 mg tea leaves/plate (mgEq) and potent inhibition was frequently achieved even with 10 mgEq/plate. Decaffeinated tea produced the same effect as observed for 'regular' teas. However, lower concentrations of some tea extracts enhanced mutagenic activity of 2-amino-3,4,7,8-tetramethyl-3H-imidazo[4,5-f]quinoxaline (4,7,8-TriMeIQx) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). Herbal tea extracts displayed variable effects on the mutagenicity of different HAA. While some extracts had no effect, others exhibited a moderate inhibitory effect on the mutagenicity of IQ-type HAA. In contrast to common tea, herbal teas showed substantial potentiating effects on the mutagenicity of several HAA, especially Trp-P-2 and 4,7,8-TriMeIQx.

Evaluation of hamburgers and hot dogs for the presence of mutagens.

Food products derived from heat-treated (fried, broiled, baked) meat may contain traces of mutagenic heterocyclic amine contaminants, some of which are proven carcinogens in rodents. To confirm their presence and range in Canadian foods, and estimate the average human intake of these types of mutagens from frequently consumed heat-processed foods, several commercially prepared fried-beef patties (hamburgers) and hot dogs (weiners) were analysed for their mutagenic capacity. The mutagenicity of the extracts was tested in the Salmonella/microsome assay using strain TA98 with metabolic activation. 16 samples of hamburgers and 14 samples of hot dogs, randomly obtained from 'fast food' commercial establishments or street vendors, were used in this survey. The mutagenic activity of these samples ranged from very low to 1042 revertants/g equivalent for the hamburgers and from non-detectable to 4875 revertants/g equivalent for the hot dogs. The average values were 199 and 424 revertants/g for the hamburgers and hot dogs, respectively. The wide range in mutagenicity was found even for the same type of product obtained from the same outlet at different times. This indicates possible inconsistency in cooking procedures during the preparation of these products. It also shows the difficulty in accurately assessing the intake of mutagenic heterocyclic amines from hamburgers and hot dogs prepared in 'fast food' outlets.

Biological significance of trace levels of mutagenic heterocyclic aromatic amines in human diet: a critical review.

Cooking of protein-rich foods may induce the formation of a series of heterocyclic aromatic amines (HAAs) that have been found to be mutagens and carcinogens. Despite very potent mutagenic activity found in the Salmonella/microsomal assay, this test cannot predict carcinogenic potency of HAAs in rodents and monkeys. Doses used in the feeding studies with animals exceeded by several orders of magnitude the levels of HAAs found in human diet, being approximately 500,000-3,000,000-fold higher than the human dietary levels. A comparison of these levels and their relevance for humans is presented. Differences in metabolic fate of different HAAs due to species and sex of the animals are discussed. These differences could account for the variable cancer-producing potential in different species. A number of still unresolved variables (such as the levels of HAAs in foods, bioavailability, possible synergistic effect from mixtures of HAAs, and metabolic fate and detoxification) preclude reliable assessment of the potential health hazard from HAAs in foods. The difference in the ability of human and animal liver microsomes to bioactivate HAAs and to form DNA adducts causes further uncertainty. The differences due to the hepatic cytochrome P-450-mediated activation of HAA among rats, monkeys and humans may influence susceptibility to cancer from these agents. HAAs occur only in traces in the human diet; however, they are present in many foods consumed daily. The levels of 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP) are approximately 100-fold higher than the levels of 2-amino-3-methylimidazo[4,5-f]-quinoline (IQ) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx). However, their mutagenic potential in the Ames Salmonella assay is reversed. Other in vitro tests, however, indicate similar genotoxicity between IQ, MeIQx and PhIP. Although most feeding studies with HAAs have been conducted with IQ and MeIQ, evidence obtained from a variety of studies indicates the possibility that PhIP may have an active role in the aetiology of human cancer and, therefore, its role as such should be evaluated. The influence of trace levels of HAAs on human health remains to be confirmed.

Role of chemopreventers in human diet.

Recent research has confirmed that many common foods contain nonnutritive components that may provide protection against chronic disease including some forms of cancer. These naturally occurring compounds, which possess anticarcinogenic and other beneficial properties, are referred to as chemopreventers. The predominant mechanism of their protective action is due to their antioxidant activity and the capacity to scavenge free radicals. Among the most investigated chemopreventers are some vitamins, plant polyphenols, flavonoids, catechins, and some components in spices. The majority of chemopreventers are available in and consumed from vegetables, fruits, grains, and tea. Various naturally occurring chemicals in garlic, soybeans, tea, and red wine appear to be responsible for the beneficial effect of these commodities on several chronic diseases. This article will review some recent studies in the search for the beneficial effects of dietary chemopreventers on human health.

Dietary effects on the uptake of benzo[a]pyrene.

It has been established that exposure to polycyclic aromatic hydrocarbons (PAHs), or more specifically benzo[a]pyrene (B[a]P), either by inhalation through cigarette smoking or by contact through occupational exposure of the lungs or skin, can result in cancerous lesions. It appears that the general population consumes more B[a]P from food than from smoking. Despite this, epidemiological studies have not implicated B[a]P from foods as a causative factor in some human cancers. This lack of an epidemiological correlation between cancer incidence and intake of dietary PAHs/B[a]P could be due to some 'protective' or 'detoxification' mechanism. Despite the abundance of literature regarding the food content of B[a]P, there are few data concerning its uptake from foods. In the present study we investigated the intestinal absorption of B[a]P from foods using bile duct cannulated rats and radioactive B[a]P. [14C]B[a]P was first added to solvents such as water, corn oil, liquid paraffin or 50% ethanol, which were the administered by gavage to rats fed diets with or without added carbon. Additionally, food polyphenols such as quercetin and chlorogenic acid were also tested for their effect on the absorption of B[a]P. The results indicated that the excretion of B[a]P in the bile was reduced by water, carbon, quercetin and chlorogenic acid but was potentiated by corn oil. To complement the in vivo studies, some in vitro tests to investigate the efficiency of B[a]P extraction from different foods using water or oil as solvents were also performed. These tests indicated that extraction of B[a]P from foods was affected by the solvent. It is postulated that reduced solubility, physical adsorption and the formation of chemical adducts between B[a]P and some food ingredients, play a sporadic, although still not well determined, role in reducing the absorption of B[a]P from the gut. The results of these studies suggest that B[a]P absorption from the intestinal tract is markedly affected by dietary components, and that this may be a factor that contributes to the lack of an epidemiological correlation between some human cancers and the B[a]P content of foods.

Antimutagens and anticarcinogens in foods.

The role of dietary factors in the prevention of major chronic diseases, cancer in particular, is under intensive investigation by many laboratories around the world. Evidence from epidemiological studies and tests in laboratory animals suggests that food consumed by the general population contains certain ingredients that may have a role in reduction of the incidence of cancer. It has been observed that a number of regular food components, belonging to different chemical groups, do possess cancer preventive and/or beneficial outcomes for some other diseases; these chemicals, therefore, are frequently collectively known as 'chemopreventers'. The mode of action of most chemopreventers is still unknown, although it appears that many of them are antioxidants, and as such, they may scavenge free radicals, formed either during the preparation of food, or by biological processes in the body. As free radicals damage lipids, proteins, cell membranes and DNA, their removal could prevent development of certain chronic diseases, particularly cancer or atherosclerosis. This review summarizes recent developments in the search for beneficial effects of regular food ingredients in prevention of cancer.

An update on research with coffee/caffeine (1989-1990).

The interest in research with coffee has been increasing in recent years, and this has resulted in a surge of publications dealing with a variety of pharmaco-physiological effects of coffee/caffeine. This review attempts to update the information on the research with coffee/caffeine, including epidemiological studies, laboratory investigations and tests with volunteers, published in 1989 and 1990. It groups published articles according to observed or investigated biological effects. The most significant findings and differences between studies are pointed out with brief commentaries on the results. The overall assessment for the safety of drinking coffee and the effect of coffee on human health, based on the literature published in 1989 and 1990, indicates that certain controversial issues are still unresolved.

Gas-liquid chromatographic-mass spectrometric determination of alpha- and beta-naphthylamines in FD&C Red No. 2 (amaranth).

A method is described for the simultaneous quantitation of trace amounts of alpha- (alpha-NA) and beta-naphthylamines (beta-NA) with detectability in the 0.1 ppb range and sensitivity of 50 picomoles in certified food grade amaranth (FD&C Red No. 2; C.I. Food Red 9; CI 16185). The amaranth sample is extracted with benzene, and the evoporated residue is derivatized with perfluorooctanoic anhydride. The resulting derivatives are separated by gas-liquid chromatography and identified and quantitated by mass spectrometric monitoring of the m/e at 539.04. The method was used for quantitation of alpha-NA and beta-NA in randomly chosen samples of amaranth. Of 11 samples from different manufacturers, 5 were free of the beta-isomer; the remaining samples contained up to 1.2 ppb beta-NA. The concentration of alpha-NA ranged from no detectable amount to 970 ppb; the majority of the samples contained less than 7 ppb.

The mutagenicity of saccharin impurities. I. Detection of mutagenic activity.

Sodium saccharin, ortho-toluenesulfonamide and impurities extracted from commercially produced saccharin with water and organic solvents were tested for mutagenicity with strains of Salmonella typhimurium. The organic solvent soluble impurities exhibited strong mutagenic activity for TA98 and slight activity for TA100. Mutagenic activity for S. typhimurium TA98 was demonstrated in extracts of some but not all lots of sodium saccharin produced by both Maumee and Remsen-Fahlberg processes. The significance of the mutagenic impurity to the carcinogenicity of saccharin is discussed.

Impurities in commercial saccharin. I. Impurities soluble in organic solvents.

Thirteen saccharin samples used for carcinogenicity tests in animals in various laboratories were analyzed for their chemical purity. Although most of the impurities were water-soluble, some were mainly soluble in organic solvents. These impurities were extracted with chloroform-methanol from a water solution of sodium saccharin. Samples obtained as acid-saccharin were converted to the sodium form before extraction. The major impurity in commercial saccharin, o-toluenesulfonamide, was also soluble in this system. Impurities were separated by gas-liquid chromatography of the underivatized, concentrated extract. Eleven major, well separated peaks were collected from the gas chromatographic column and identified by mass spectroscopy. Some of the peaks were compared with known standards. Qualitative and quantitative differences in impurities were observed among different saccharin samples. The identified impurities (in order of appearance from the gas-liquid chromatographic column) were as follows: o-toluenesulfonamide; p-toluenesufonamide; 1,2-benzisothiazole 1,1-dioxide; 1,2-benzisothiazoline 1,1-dioxide; diphenylsulfone; 0,0'-ditolylsulfone; o,m'-ditolylsulfone, o,p'-ditolylsulfone; m,p'-ditolylsulfone; p,p'-ditolylsulfone, and tetracosane.