Validity of a self-administered food frequency questionnaire in the assessment of heterocyclic amine intake using 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) levels in hair

The Cooked Meat Carcinogen 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine Hair Dosimeter, DNA Adductomics Discovery, and Associations with Prostate Cancer Pathology Biomarkers

Well-done cooked red meat consumption is linked to aggressive prostate cancer (PC) risk. Identifying mutation-inducing DNA adducts in the prostate genome can advance our understanding of chemicals in meat that may contribute to PC. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a heterocyclic aromatic amine (HAA) formed in cooked meat, is a potential human prostate carcinogen. PhIP was measured in the hair of PC patients undergoing prostatectomy, bladder cancer patients under treatment for cystoprostatectomy, and patients treated for benign prostatic hyperplasia (BPH). PhIP hair levels were above the quantification limit in 123 of 205 subjects. When dichotomizing prostate pathology biomarkers, the geometric mean PhIP hair levels were higher in patients with intermediate and elevated-risk prostate-specific antigen values than lower-risk values <4 ng/mL (p = 0.03). PhIP hair levels were also higher in patients with intermediate and high-risk Gleason scores ≥7 compared to lower-risk Gleason score 6 and BPH patients (p = 0.02). PC patients undergoing prostatectomy had higher PhIP hair levels than cystoprostatectomy or BPH patients (p = 0.02). PhIP-DNA adducts were detected in 9.4% of the patients assayed; however, DNA adducts of other carcinogenic HAAs, and benzo[a]pyrene formed in cooked meat, were not detected. Prostate specimens were also screened for 10 oxidative stress-associated lipid peroxidation (LPO) DNA adducts. Acrolein 1,N²-propano-2'-deoxyguanosine adducts were detected in 54.5% of the patients; other LPO adducts were infrequently detected. Acrolein adducts were not associated with prostate pathology biomarkers, although DNA adductomic profiles differed between PC patients with low and high-grade Gleason scores. Many DNA adducts are of unknown origin; however, dG adducts of formaldehyde and a series of purported 4-hydroxy-2-alkenals were detected at higher abundance in a subset of patients with elevated Gleason scores. The PhIP hair biomarker and DNA adductomics data support the paradigm of well-done cooked meat and oxidative stress in aggressive PC risk.

Biomarkers of meat and seafood intake: an extensive literature review

Meat, including fish and shellfish, represents a valuable constituent of most balanced diets. Consumption of different types of meat and fish has been associated with both beneficial and adverse health effects. While white meats and fish are generally associated with positive health outcomes, red and especially processed meats have been associated with colorectal cancer and other diseases. The contribution of these foods to the development or prevention of chronic diseases is still not fully elucidated. One of the main problems is the difficulty in properly evaluating meat intake, as the existing self-reporting tools for dietary assessment may be imprecise and therefore affected by systematic and random errors. Dietary biomarkers measured in biological fluids have been proposed as possible objective measurements of the actual intake of specific foods and as a support for classical assessment methods. Good biomarkers for meat intake should reflect total dietary intake of meat, independent of source or processing and should be able to differentiate meat consumption from that of other protein-rich foods; alternatively, meat intake biomarkers should be specific to each of the different meat sources (e.g., red vs. white; fish, bird, or mammal) and/or cooking methods. In this paper, we present a systematic investigation of the scientific literature while providing a comprehensive overview of the possible biomarker(s) for the intake of different types of meat, including fish and shellfish, and processed and heated meats according to published guidelines for biomarker reviews (BFIrev). The most promising biomarkers are further validated for their usefulness for dietary assessment by published validation criteria.

Association between NAT2, CYP1A1, and CYP1A2 genotypes, heterocyclic aromatic amines, and prostate cancer risk: a case control study in Japan

Background

Heterocyclic aromatic amines (HAAs) may confer prostate cancer risk; however, the evidence is inconclusive and the activity of HAA-metabolizing enzymes is modulated by gene variants. The purpose of our study was to determine whether there was evidence of an association between HAA intake, polymorphisms in NAT2, CYP1A1, and CYP1A2 and prostate cancer risk in Japanese men.

Methods

Secondary data analysis of an observational case control study was performed. Among 750 patients with prostate cancer and 870 healthy controls, 351 cases and 351 age-matched controls were enrolled for analysis. HAA intake was estimated using a food frequency questionnaire and genotypes were scored by TaqMan real-time PCR assay. Logistic regression analysis was conducted according to affected/control status.

Results

We found that high HAA intake was significantly associated with an increased risk of prostate cancer (odds ratio (OR), 1.90; 95% confidence interval (95% CI), 1.40–2.59). The increased risk of prostate cancer was observed among individuals with the NAT2 slow acetylator phenotype (OR, 1.65; 95% CI, 1.04–2.61), CYP1A1 GA + GG genotype (OR, 1.27; 95% CI, 1.02–1.59), and CYP1A2 CA + AA genotype (OR, 1.43; 95% CI, 1.03–2.00). In addition, CYP1A1 GA + GG genotypes were associated with increased cancer risk in low (OR, 2.05; 95% CI, 1.19–3.63), moderate (OR, 1.72; 95% CI, 1.07–2.76), and high (OR, 2.86; 95% CI, 1.83–4.47) HAA intake groups.

Conclusions

Our results suggest that high HAA intake is a risk factor of prostate cancer, and genotypes related to HAA metabolic enzymes can modulate the degree of the risk.

Susceptibility to human cancer: From the perspective of a pathologist

The etiologies of human cancer can only be discerned when the genetic clustering of cancer occurs within a family or when cancer occurs endemically in a particular environment. The possible approaches to solving the nature/nurture problem, especially for human carcinogenesis, posit a fascinating challenge for pathologists. This perspective review presents some examples of how clues to human cancer etiologies and/or susceptibilities reside in the realm of pathology practice. These examples using various omics techniques including adductomics, which I would like to highlight in this article, show that the currently available concepts and methods in human pathology can open a path toward the brave new world of a post-genomic era of medicine for young pathologists, whether their original intention was toward the pursuit of diagnostic or investigative knowledge.

Dose validation of PhIP hair level as a biomarker of heterocyclic aromatic amines exposure: a feeding study

Hair measurement of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a promising biomarker of exposure to this carcinogen formed in cooked meats. However, the dose relationship between normal range intake and hair levels and the modulating effects of CYP1A2 metabolism and hair melanin need to be evaluated. We conducted a randomized, cross-over feeding study among 41 non-smokers using ground beef cooked to two different levels of doneness, 5 days a week for 1 month. PhIP was measured by liquid chromatography/mass spectrometry in food (mean low dose = 0.72 µg/serving; mean high dose = 2.99 µg/serving), and change in PhIP hair level was evaluated. CYP1A2 activity was assessed in urine with the caffeine challenge test and head hair melanin was estimated by UV spectrophotometry. We observed a strong dose-dependent increase in hair PhIP levels. This increase was highly correlated with dose received (ρ = 0.68, P < 0.0001). CYP1A2 activity and normalizing for hair melanin did not modify the response to the intervention. Consumption of PhIP at doses similar to those in the American diet results in a marked dose-dependent accumulation of PhIP in hair. Hair PhIP levels may be used as a biomarker of dietary exposure in studies investigating disease risk.

Biomonitoring the cooked meat carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in canine fur

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a heterocyclic aromatic amine (HAA) that is formed during the cooking of meat, poultry, and fish. PhIP is a rodent carcinogen and is thought to contribute to several diet-related cancers in humans. PhIP is present in the hair of human omnivores but not in the hair of vegetarians. We have now identified PhIP in the fur of 14 out of 16 healthy dogs consuming different brands of commercial pet food. The levels of PhIP in canine fur varied by over 85-fold and were comparable to the levels of PhIP present in human hair. However, high density fur containing PhIP covers a very high proportion of the body surface area of dogs, whereas high density terminal hair primarily covers the scalp and pubis body surface area of humans. These findings signify that the exposure and bioavailability of PhIP are high in canines. A potential role for PhIP in the etiology of canine cancer should be considered.

Comparability and repeatability of methods for estimating the dietary intake of the heterocyclic amine contaminant 2-amino-1-methyl-6-phenylimidazo[4,5b]pyridine (PhIP)

Inconsistent risk estimates for dietary heterocyclic amine (HCA) exposure and cancers may be due to differences in exposure assessment methods and the associated measurement error. We evaluated repeatability and comparability of intake estimates of the HCA 2-amino-1-methyl-6-phenylimidazo[4,5b]pyridine (PhIP) among two food frequency questionnaire (FFQ) collections, three diary collections, and three measurements of urinary PhIP and its metabolites in 36 non-smokers in Baltimore, Maryland, during 2004-2005. Collections spanned ∼9 months. Method repeatability was characterised with intraclass correlation coefficients (ICCs). Comparability among methods was assessed with Spearman correlation coefficients. Within-subject variability in PhIP intake was comparably high across all methods (ICCs of 0.20, 0.30, and 0.15 for FFQ, diary, and creatinine-adjusted urinary PhIP, respectively). Mean diary-based PhIP intake and mean urinary PhIP concentration were strongly correlated when restricting the analysis to participants with at least one non-zero diary-based estimate of PhIP intake (n = 15, r = 0.75, p = 0.001), but not in the full study population (n = 36, r = 0.18, p = 0.28). Mean PhIP intake from the FFQ was not associated with that either based on the diary or urinary PhIP separately, but was modestly correlated with a metric that combined the diary- and biomarker-based approaches (r = 0.30, p = 0.08). The high within-subject variability will result in significantly attenuated associations if a single measure is used to estimate exposure within an epidemiologic study. Improved HCA assessment tools, such as a combination of methods or validated biomarkers that capture long term exposure, are needed.

Meat consumption, heterocyclic amines and colorectal cancer risk: the Multiethnic Cohort Study

Greater consumption of red and processed meat has been associated with an increased risk of colorectal cancer in several recent meta-analyses. Heterocyclic amines (HCAs) have been hypothesized to underlie this association. In this prospective analysis conducted within the Multiethnic Cohort Study, we examined whether greater consumption of total, red or processed meat was associated with the risk of colorectal cancer among 165,717 participants who completed a detailed food frequency questionnaire at baseline. In addition, we examined whether greater estimated intake of HCAs was associated with the risk of colorectal cancer among 131,763 participants who completed a follow-up questionnaire that included a meat-cooking module. A total of 3,404 and 1,757 invasive colorectal cancers were identified from baseline to the end of follow-up and from the date of administration of the meat-cooking module to the end of follow-up, respectively. Proportional hazard models were used to estimate basic and multivariable-adjusted relative risks (RRs) and 95% confidence intervals for colorectal cancer associated with dietary exposures. In multivariable models, no association with the risk of colorectal cancer was detected for density-adjusted total meat (RR(Q5 vs. Q1) = 0.93 [0.83-1.05]), red meat (RR = 1.02 [0.91-1.16]) or processed meat intake (RR = 1.06 [0.94-1.19]) or for total (RR = 0.90 [0.76-1.05]) or specific HCA intake whether comparing quintiles of dietary exposure or using continuous variables. Although our results do not support a role for meat or for HCAs from meat in the etiology of colorectal cancer, we cannot rule out the possibility of a modest effect.

Metabolism and biomarkers of heterocyclic aromatic amines in molecular epidemiology studies: lessons learned from aromatic amines

Aromatic amines and heterocyclic aromatic amines (HAAs) are structurally related classes of carcinogens that are formed during the combustion of tobacco or during the high-temperature cooking of meats. Both classes of procarcinogens undergo metabolic activation by N-hydroxylation of the exocyclic amine group to produce a common proposed intermediate, the arylnitrenium ion, which is the critical metabolite implicated in toxicity and DNA damage. However, the biochemistry and chemical properties of these compounds are distinct, and different biomarkers of aromatic amines and HAAs have been developed for human biomonitoring studies. Hemoglobin adducts have been extensively used as biomarkers to monitor occupational and environmental exposures to a number of aromatic amines; however, HAAs do not form hemoglobin adducts at appreciable levels, and other biomarkers have been sought. A number of epidemiologic studies that have investigated dietary consumption of well-done meat in relation to various tumor sites reported a positive association between cancer risk and well-done meat consumption, although some studies have shown no associations between well-done meat and cancer risk. A major limiting factor in most epidemiological studies is the uncertainty in quantitative estimates of chronic exposure to HAAs, and thus, the association of HAAs formed in cooked meat and cancer risk has been difficult to establish. There is a critical need to establish long-term biomarkers of HAAs that can be implemented in molecular epidemioIogy studies. In this review, we highlight and contrast the biochemistry of several prototypical carcinogenic aromatic amines and HAAs to which humans are chronically exposed. The biochemical properties and the impact of polymorphisms of the major xenobiotic-metabolizing enzymes on the biological effects of these chemicals are examined. Lastly, the analytical approaches that have been successfully employed to biomonitor aromatic amines and HAAs, and emerging biomarkers of HAAs that may be implemented in molecular epidemiology studies are discussed.

Intake of heterocyclic aromatic amines and the risk of prostate cancer in the EPIC-Heidelberg cohort

BACKGROUND

Heterocyclic amines (HCA) are positively associated with prostate cancer risk in animal models. Because of mostly inconsistent results of epidemiological studies, we examined the association between intake of HCA and prostate cancer risk.

METHODS

In the EPIC-Heidelberg cohort, detailed information on diet, anthropometry, and lifestyle was assessed between 1994 and 1998. Dietary HCA intake was estimated using information on meat consumption, cooking methods, and preferred degree of browning. During 104,195 person-years of follow-up, 337 incident cases of prostate cancer (123 advanced cases) were identified among 9,578 men with valid dietary information. Multivariate Cox proportional hazards regression was used to examine the association between intake of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-3,4,8-dimethylimidazo[4,5-f]quinoxaline (DiMeIQx) and prostate cancer.

RESULTS

Men in the highest quartiles of PhIP, MeIQx, and DiMeIQx intake, respectively, had no increased risk of prostate cancer compared with men in the lowest quartiles (HR = 0.89, 95% CI 0.66-1.22 [PhIP]; 1.06, 0.77-1.45 [MeIQx]; 0.98, 0.72-1.34 [DiMeIQx]). There were no associations between HCA intake and advanced prostate cancer or between high consumption of strongly browned meat and prostate cancer.

DISCUSSION

Our data do not support the hypothesis that HCA intake as consumed in a regular diet is a risk factor for prostate cancer.

Biomonitoring of carcinogenic heterocyclic aromatic amines in hair: a validation study

A facile method was established to measure heterocyclic aromatic amines (HAAs) accumulated in human hair and rodent fur. The samples were digested by base hydrolysis, and the liberated HAAs were isolated by tandem solvent/solid-phase extraction. Quantification was done by liquid chromatography/tandem mass spectrometry, using a triple stage quadrupole mass spectrometer in the selected reaction monitoring mode. In a pilot study of 12 human volunteers, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was detected in the hair of six meat-eaters at levels ranging from 290 to 890 pg/g hair. 2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-9H-pyrido[2,3-b]indole (AalphaC) were below the limit of quantification (LOQ) (50 pg/g hair) in hair from meat-eaters and six vegetarians. PhIP was detected in the hair from one vegetarian, and at a level just above the LOQ (65 pg/g hair), indicating that PhIP exposure occurs primarily through meat consumption. The levels of PhIP in hair samples from two meat-eaters varied by less than 24% over a 6 month interval, signifying that the exposure to PhIP and its accumulation in hair are relatively constant over time. In a controlled feeding study, female C57BL/6 mice were given these HAAs in their drinking water for 1 month, at six daily dose concentrations ranging from 0 and 0.080 to 800 microg/kg body weight. PhIP was detected in fur of mice at all doses, whereas AalphaC and MeIQx were detected in fur at dosages > or =0.8 mug AalphaC/kg body weight and > or =8 microg MeIQx/kg body weight. There was a strong positive relationship between dosage and each of the HAAs accumulated in fur and their DNA adducts formed in liver and colon (p values < 0.0001); however, the levels of HAA in fur did not correlate to the levels of DNA adducts after adjustment of dose. Thus, hair appears to be a promising tissue with by which we can noninvasively biomonitor the chronic exposure to PhIP, a potential human carcinogen.

Association between dietary heterocyclic amine levels, genetic polymorphisms of NAT2, CYP1A1, and CYP1A2 and risk of stomach cancer: a hospital-based case-control study in Japan

BACKGROUND

Although the associations between grilled (broiled) or barbecued meats or fish intake and stomach cancer risk have been investigated, the evidence implicating heterocyclic amine (HCA) intake as a cause of stomach cancer is limited. We conducted a case-control study to investigate the association between HCA intake and stomach cancer risk. We also investigated the possible effect of genetic polymorphisms of NAT2, CYP1A1, and CYP1A2 on stomach cancer.

METHODS

HCA exposure data were assessed using a self-administered food-frequency questionnaire, and estimated HCA intake was verified by measuring 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) values in human hair. A total of 149 cases and 296 controls were included in the analyses. Odds ratios (ORs) were calculated, using conditional logistic regression analysis, to compare intake levels between the first and third tertiles.

RESULTS

Results showed no statistically significant increase in the risk of stomach cancer with respect to total HCA intake (OR, 1.11; 95% confidence interval [CI], 0.36, 3.49), or with respect to the intake of individual HCAs; namely, PhIP, 2-amino-3, 4-dimethylimidazo[4,5-f]quinoline (MeIQ), and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx). Genetic polymorphisms of NAT2, CYP1A1, and CYP1A2 did not influence the association of HCA intake with stomach cancer.

CONCLUSION

In the present study, with a limited sample size of subjects with low HCA exposure, no association was found between HCA intake and stomach cancer, nor was there any evidence of any influence by genetic polymorphisms of NAT2, CYP1A1, and CYP1A2 on the risk of stomach cancer.

Association between dietary heterocyclic amine levels, genetic polymorphisms of NAT2, CYP1A1, and CYP1A2 and risk of colorectal cancer: a hospital-based case-control study in Japan

OBJECTIVE

Although associations between dietary HCA intake and colorectal cancer risk have been investigated, results have been suggestive but inconsistent. The aim of this hospital-based case-control study was to examine the impact of heterocyclic amine (HCA) intake on colorectal cancer risk. A further objective was to investigate the possible effect of genetic polymorphisms of NAT2, CYP1A1, and CYP1A2 on colorectal cancer.

MATERIAL AND METHODS

HCA exposure data were assessed using a self-administered food frequency questionnaire, and estimated HCA intake was verified by measuring the PhIP value in human hair. A total of 117 cases and 238 controls were included in these analyses. Odds ratios (ORs) were calculated using conditional logistic regression analysis to compare intake levels between the first and third tertiles.

RESULTS

No statistically significant increase in the risk of colorectal cancer with respect to total HCA intake was shown by analysis (OR = 0.99, 95% CI = 0.21-4.81). Furthermore, no association with risk was seen for individual HCAs, including PhIP, MeIQ, and MeIQx. Although variant alleles of CYP1A2 were associated with colorectal cancer (OR = 0.27; 95% CI = 0.07-0.99), genetic polymorphisms of NAT2, CYP1A1, and CYP1A2 did not influence the association of HCA intake with colorectal cancer.

CONCLUSIONS

In the present study in subjects with low HCA exposure and with a limited sample size, no association was found between HCA intake and colorectal cancer, or any evidence of influence by genetic polymorphisms of NAT2, CYP1A1, and CYP1A2.

Heterocyclic amines content of meat and fish cooked by Brazilian methods

Heterocyclic amine (HCA) concentrations were measured in meat and fish samples cooked by pan-frying, grilling and churrasco (Brazilian barbecue) to various levels of doneness in accordance with the cooking methods most commonly used in Brazil. HCAs were extracted by the Blue-rayon absorption method and measured by liquid chromatography-mass spectrometry. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) were sharply increased in very well-done meats and fish. HCA levels varied somewhat across cooking methods: levels of PhIP (ng/g) in very well-done, non-marinated samples were particularly high for churrasco (31.8 in the exterior of the sample), compared to lower levels for grilled (16.3), and pan-fried beef (0.58). On comparison across foods, chicken contained higher HCA levels than other non-marinated samples. For example, PhIP levels (ng/g) in very well-done pan-fried foods were 34.6 for chicken with the skin, 0.58 for beef, 7.25 for pork, 2.28 for sardines, and 7.37 for salmon cooked with the skin. HCA levels were lower in marinated meats and fish than in non-marinated samples, except for pan-fried salmon. This study provides valuable information which will allow the estimation of dietary HCA exposure using an epidemiologic questionnaire and the investigation of the association of HCA intake with cancer risk in Brazil.

Well-done meat intake, heterocyclic amine exposure, and cancer risk

High intake of meat, particularly red and processed meat, has been associated with an increased risk of a number of common cancers such as breast, colorectum, and prostate in many epidemiological studies. Heterocyclic amines (HCAs) are a group of mutagenic compounds found in cooked meats, particularly well-done meats. HCAs are some of most potent mutagens detected using the Ames/salmonella tests and have been clearly shown to induce tumors in experimental animal models. Over the past 10 years, an increasing number of epidemiological studies have evaluated the association of well-done meat intake and meat carcinogen exposure with cancer risk. The results from these epidemiologic studies were evaluated and summarized in this review. The majority of these studies have shown that high intake of well-done meat and high exposure to meat carcinogens, particularly HCAs, may increase the risk of human cancer.

Biomarkers of meat intake and the application of nutrigenomics

Objective dietary intake markers for meat would be useful to assess meat intake in observational studies and as compliance markers in dietary intervention studies. A number of compounds are specific to meat compared with most other dietary items but there is some overlap between protein rich foods. A number of single compounds have been analysed in urine, plasma, serum or hair samples in studies of their relationship to meat or total protein intake. Among potential markers of dietary meat intake are urea, creatine, creatinine, carnitine, carnosine, anserine, ophidine, 1- and 3-methylhistidine, and sulphate or sulphite. Anserine and 1-methylhistidine come close to being meat-specific markers but true quantitative biomarker may not exist. Modern profiling techniques are increasingly used to look for useful biomarkers or for constructing them from latent information in complex profiles. Metabolomics by NMR spectroscopy of urine has also been applied to search for meat intake markers. Studies on single compounds or metabolomics markers are shortly reviewed here.

Ability of probiotic Lactobacillus casei DN 114001 to bind or/and metabolise heterocyclic aromatic amines in vitro

INTRODUCTION

Heterocyclic aromatic amines (HCA) are compounds with high mutagenic potential, formed when meat is cooked at high temperatures of 150-300 degrees C. These compounds contribute to development of colon and gastric cancer. Western diet provides a lot of HCA and influences the available substrates for the intestinal microbiota which can activate HCA to direct acting mutagens. On the other hand, lactic acid bacteria existing in the colon and ingested with food including probiotics, may exert an anti-carcinogenic action, but the mechanism is still poorly understood.

MATERIALS AND METHODS

In the present study we determined the ability of probiotic Lactobacillus casei DN 114001 (Actimel strain) to metabolise or adsorb three HCA: IQ, MelQx and PhIP in vitro. Lactobacilli were cultivated in MRS and in a modified MRS broth with reduced concentrations of nitrogen and carbon (MRS NC), with addition of 25 mug/ml of IQ, MelQx or PhIP. Their concentration after cultivation with L. casei DN 114001 was measured with high-performance liquid chromatography and the genotoxicity was evaluated by the alkaline comet assay.

RESULTS AND CONCLUSIONS

It was measured, that after 24 h cultivation in MRS (cell density was 10(9) cfu/ml), rapid decrease of IQ and PhIP (98-99%) was observed, and the peaks on chromatograms were almost completely reduced. In case of MeIQx the decrease was about 27%. In a modified MRS broth (cell density was 10(8) cfu/ml), the ability to decrease HCA concentration during prolonged cultivation (to 168 h) depended on the growth phase of bacteria, and it was about 51.5% for IQ and at about 11.2% for MeIQx. Non-growing cells (in phosphate buffer), could reduce the content of IQ and PhIP from 72 h to the end of incubation. L. casei DN 114001 reduced genotoxicity of HCA (IQ from 46 to 48%; MeIQx from 35 to 65% and PhIP from 32 to 81%), and the degree depended on the incubation time, cell growth and the medium used. It may suggest that bacteria can metabolise or adsorb HCA.

Formação de toxinas durante o processamento de alimentos e as possíveis conseqüências para o organismo humano

A produção de alimentos envolve inúmeras reações químicas, durante as quais podem ser geradas substâncias tóxicas ao organismo humano. A produção destas substâncias pode ocorrer de diferentes maneiras, variando em quantidade e em grau de toxicidade. Este trabalho objetivou estudar a produção de toxinas no processamento de alimentos, assim como as conseqüências da ingestão dessas substâncias para o ser humano. O estudo foi realizado a partir de extensa pesquisa bibliográfica. As principais reações na formação de compostos tóxicos apresentadas no decorrer do estudo são: degradação de lipídios, hidrogenação, pirólise e defumação. Entre as substâncias formadas, destacam-se: peróxidos, ácidos graxos trans, aminas heterocíclicas e hidrocarbonetos aromáticos policíclicos. O profissional nutricionista necessita conhecer como ocorre a formação de toxinas durante os variados processamentos que envolvem alimentos, assim como os riscos para a saúde de quem consome essas substâncias. Também é preciso propor técnicas de processamento adequadas, visando ao bem-estar do consumidor e à manutenção das propriedades nutricionais do alimento.