Meat-related mutagens/carcinogens in the etiology of colorectal cancer

Meat intake, cooking methods, dietary carcinogens, and colorectal cancer risk: findings from the Colorectal Cancer Family Registry

Diets high in red meat and processed meats are established colorectal cancer (CRC) risk factors. However, it is still not well understood what explains this association. We conducted comprehensive analyses of CRC risk and red meat and poultry intakes, taking into account cooking methods, level of doneness, estimated intakes of heterocyclic amines (HCAs) that accumulate during meat cooking, tumor location, and tumor mismatch repair proficiency (MMR) status. We analyzed food frequency and portion size data including a meat cooking module for 3364 CRC cases, 1806 unaffected siblings, 136 unaffected spouses, and 1620 unaffected population-based controls, recruited into the CRC Family Registry. Odds ratios (OR) and 95% confidence intervals (CI) for nutrient density variables were estimated using generalized estimating equations. We found no evidence of an association between total nonprocessed red meat or total processed meat and CRC risk. Our main finding was a positive association with CRC for pan-fried beefsteak (P(trend) < 0.001), which was stronger among MMR deficient cases (heterogeneity P = 0.059). Other worth noting associations, of borderline statistical significance after multiple testing correction, were a positive association between diets high in oven-broiled short ribs or spareribs and CRC risk (P(trend) = 0.002), which was also stronger among MMR-deficient cases, and an inverse association with grilled hamburgers (P(trend) = 0.002). Our results support the role of specific meat types and cooking practices as possible sources of human carcinogens relevant for CRC risk.

Urinary 1-methylhistidine and 3-methylhistidine, meat intake, and colorectal adenoma risk

Self-reported red and processed meat intake has been positively associated with colorectal adenoma and cancer; however, measurement error in self-reported data can attenuate risk estimates, increasing the need for improved exposure assessment methods to better understand this association. A controlled feeding study revealed that urinary 1-methylhistidine and 3-methylhistidine levels were dose-dependently associated with meat intake; our aim was to examine these analytes in relation to colorectal adenoma. Individuals undergoing routine cancer screening by sigmoidoscopy or colonoscopy were recruited for a colorectal adenoma case-control study; participants completed a food frequency questionnaire and a meat questionnaire, and donated urine. Urinary 1-methylhistidine and 3-methylhistidine levels were measured in 131 case-control pairs (age, sex, and smoking matched); odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by logistic regression. Although the mean self-reported red meat intake was higher in cases (59 g/day) than in controls (48 g/day), the mean urinary 1-methylhistidine and 3-methylhistidine levels did not differ by case status (P=0.72). Neither urinary 1-methylhistidine nor urinary 3-methylhistidine was associated with colorectal adenoma (OR continuous=0.90, 95% CI: 0.53-1.54; OR continuous=0.90, 95% CI: 0.69-1.17, respectively). A variable combining self-reported red meat intake with urinary 1-methylhistidine and 3-methylhistidine levels was not associated with colorectal adenoma. Analyzing urine samples from multiple days from 17 individuals revealed intraclass correlations of 0.52 and 0.49 for 1-methylhistidine and 3-methylhistidine, respectively; this variability could result in attenuated risks. Urinary 1-methylhistidine and 3-methylhistidine levels, measured in one sample, were not associated with colorectal adenoma.

Detoxification of chlorella supplement on heterocyclic amines in Korean young adults

Heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) have been established as carcinogenic chemicals in Western diet. This study was performed to estimate HCA exposure levels in Korean daily life and to assess the ability of Chlorella vulgaris to detoxify carcinogenic HCAs in a randomized, double blind, placebo-controlled crossover study with chlorella supplement (N=6, all females, age: 27.17±7.73yr) for 2 weeks. We analyzed HCAs in hydrolyzed urine specimens using LC/TOF-MS. As results, urinary levels of MeIQx, PhIP, and IQx-8-COOH were 323.36±220.11ng/L, 351.59±254.93ng/L, and 130.85±83.22ng/L, respectively. Effects of chlorella to reduce urinary MeIQx were marginally significant (before, 430±226.86pg/mL vs. after, 174.45±101.65pg/mL: 0.05<p<0.1). However, urinary levels of PhIP or IQx-8-COOH, a major metabolite of MeIQx, were not changed by chlorella supplementation. In conclusion, our study demonstrates that current daily levels of HCA exposure in Korean young adults are not lower than those in the Western world. In addition, the effects of chlorella's to detoxify HCAs likely occur by interfering e with absorption or metabolism.

Respiratory risks from household air pollution in low and middle income countries

A third of the world's population uses solid fuel derived from plant material (biomass) or coal for cooking, heating, or lighting. These fuels are smoky, often used in an open fire or simple stove with incomplete combustion, and result in a large amount of household air pollution when smoke is poorly vented. Air pollution is the biggest environmental cause of death worldwide, with household air pollution accounting for about 3·5-4 million deaths every year. Women and children living in severe poverty have the greatest exposures to household air pollution. In this Commission, we review evidence for the association between household air pollution and respiratory infections, respiratory tract cancers, and chronic lung diseases. Respiratory infections (comprising both upper and lower respiratory tract infections with viruses, bacteria, and mycobacteria) have all been associated with exposure to household air pollution. Respiratory tract cancers, including both nasopharyngeal cancer and lung cancer, are strongly associated with pollution from coal burning and further data are needed about other solid fuels. Chronic lung diseases, including chronic obstructive pulmonary disease and bronchiectasis in women, are associated with solid fuel use for cooking, and the damaging effects of exposure to household air pollution in early life on lung development are yet to be fully described. We also review appropriate ways to measure exposure to household air pollution, as well as study design issues and potential effective interventions to prevent these disease burdens. Measurement of household air pollution needs individual, rather than fixed in place, monitoring because exposure varies by age, gender, location, and household role. Women and children are particularly susceptible to the toxic effects of pollution and are exposed to the highest concentrations. Interventions should target these high-risk groups and be of sufficient quality to make the air clean. To make clean energy available to all people is the long-term goal, with an intermediate solution being to make available energy that is clean enough to have a health impact.

Dietary exposure of Nigerians to mutagens and estrogen-like chemicals

Food and drinking water are poorly delineated sources of human exposure to chemical food mutagens and endocrine-disrupting chemicals. In this study, we investigated the presence of mutagens and chemicals exhibiting estrogenic activity in the daily diet of Nigerians, using in vitro assays. Commercially processed foods or snacks and various brands of pure water sachets were extracted by solid-phase extraction and liquid-liquid extraction, respectively. Mutagenicity was determined by the conventional Ames test and two complementary assays on two strains of Salmonella (TA 100 and TA 98), while the estrogenic activity was assessed by a yeast bioluminescent assay, using two recombinant yeast strains (Saccharomyces cerevisiae BMAEREluc/ERα and S. cerevisiae BMA64/luc). A third of the food varieties investigated (chin-chin, hamburger, suya and bean cake) were mutagenic in all three assays, either in the presence or absence of S9 mix. Of the packed water samples, five out of the sixteen investigated (31%), were found to be estrogenic, with estradiol and bisphenol A equivalents ranging from 0.79 to 44.0 ng/L and 124.2 to 1,000.8 ng/L, respectively. Hence, although the current situation in Nigeria does not appear to be substantially worse than, e.g., in Europe, regular monitoring is warranted in the future.

Fecal metabolomics: assay performance and association with colorectal cancer

Metabolomic analysis of feces may provide insights on colorectal cancer (CRC) if assay performance is satisfactory. In lyophilized feces from 48 CRC cases, 102 matched controls, and 48 masked quality control specimens, 1043 small molecules were detected with a commercial platform. Assay reproducibility was good for 527 metabolites [technical intraclass correlation coefficient (ICC) >0.7 in quality control specimens], but reproducibility in 6-month paired specimens was lower for the majority of metabolites (within-subject ICC ≤0.5). In the CRC cases and controls, significant differences (false discovery rate ≤0.10) were found for 41 of 1043 fecal metabolites. Direct cancer association was found with three fecal heme-related molecules [covariate-adjusted 90th versus 10th percentile odds ratio (OR) = 17-345], 18 peptides/amino acids (OR = 3-14), palmitoyl-sphingomyelin (OR = 14), mandelate (OR = 3) and p-hydroxy-benzaldehyde (OR = 4). Conversely, cancer association was inverse with acetaminophen metabolites (OR <0.1), tocopherols (OR = 0.3), sitostanol (OR = 0.2), 3-dehydrocarnitine (OR = 0.4), pterin (OR = 0.3), conjugated-linoleate-18-2N7 (OR = 0.2), N-2-furoyl-glycine (OR = 0.3) and p-aminobenzoate (PABA, OR = 0.2). Correlations suggested an independent role for palmitoyl-sphingomyelin and a central role for PABA (which was stable over 6 months, within-subject ICC 0.67) modulated by p-hydroxy-benzaldehyde. Power calculations based on ICCs indicate that only 45% of metabolites with a true relative risk 5.0 would be found in prospectively collected, prediagnostic specimens from 500 cases and 500 controls. Thus, because fecal metabolites vary over time, very large studies will be needed to reliably detect associations of many metabolites that potentially contribute to CRC.

Prostate cancer and the influence of dietary factors and supplements: a systematic review

Background

Prostate cancer is the second most common cause of cancer worldwide after lung cancer. There is increasing evidence that diet and lifestyle plays a crucial role in prostate cancer biology and tumourigenesis. Prostate cancer itself represents a good model of cancer in which to look for chemopreventive agents due to the high disease prevalence, slowly progressive nature, and long latency period. Dietary agents have gained considerable attention, often receiving much publicity in the media.

Aim

To review the key evidence available for potential chemopreventive nutrients.

Methods

The methodology for this review involved a PubMed search from 1990 to 2013 using the key-words “diet and prostate cancer”, “nutrition and prostate cancer”, “dietary factors and prostate cancer”, “prostate cancer epidemiology”, “prostate cancer prevention”, “prostate cancer progression”.

Results

Red meat, dietary fat and milk intake should be minimised as they appear to increase the risk of prostate cancer. Fruit and vegetables and polyphenols may be preventive in prostate cancer, but further studies are needed to draw more solid conclusions and to clarify their role in patients with an established diagnosis of prostate cancer. Selenium and vitamin supplements cannot be advocated for the prevention of prostate cancer and indeed higher doses may be associated with a worse prognosis. There is no specific evidence regarding benefits of probiotics or prebiotics in prostate cancer.

Conclusions

From the wealth of evidence available, many recommendations can be made although more randomised control trials are required. These need to be carefully designed due to the many confounding factors and heterogeneity of the population.

Vegetarianism as a protective factor for colorectal adenoma and advanced adenoma in Asians

BACKGROUND

Although epidemiologic and animal studies suggest a vegetarian diet protects against the development of colorectal cancer, the relationship between vegetarian diet and incidence of colorectal adenoma is not yet conclusive, especially for Asians.

AIM

The purpose of this study was to examine the protective effect of a vegetarian diet against colorectal adenoma and advanced adenoma.

METHODS

This cross-sectional study compared the prevalence of colorectal adenoma among Buddhist priests, who are obligatory vegetarians, with that among age and sex-matched controls. All the subjects underwent health checkups in a health-promotion center in Korea.

RESULT

Colorectal adenoma and advanced adenoma were both more prevalent in the general population group than in the Buddhist priest group (25.2 vs. 17.9 %, 6.7 vs. 2.0 %). However, the prevalence of metabolic syndrome, high body mass index, and waist circumference were higher in the Buddhist priest group. According to univariate analysis, non-vegetarian diet (general population) significantly increased the prevalence of colorectal adenoma and advanced adenoma compared with a vegetarian diet (Buddhist priests) (OR 1.54, 95 % CI 1.08-2.21, P = 0.018; OR 3.60, 95 % CI 1.53-8.48, P = 0.003). In a conditional regression analysis model, non-vegetarian diet was also a significant risk factor for colorectal adenoma and advanced adenoma (OR 1.52, 95 % CI 0.75-2.07, P = 0.043; OR 2.94, CI 0.97-7.18, P = 0.036).

CONCLUSIONS

Vegetarianism may be effective in preventing both colorectal adenoma and advanced adenoma in Asians.

Systematic review with meta-analysis: meat consumption and the risk of hepatocellular carcinoma

BACKGROUND

The association between meat consumption and the risk of hepatocellular carcinoma (HCC) is still inconclusive.

AIM

To conduct a systematic review and meta-analysis to quantitatively assess the relationship between meat intake and the risk of HCC.

METHODS

We searched the PubMed, Web of Science and EMBASE databases for relevant studies published before July 2013. The summary relative risks were pooled using the fixed-effects model when no substantial heterogeneity was detected, otherwise, the random-effects model was used. Heterogeneity and publication bias were also analysed.

RESULTS

Finally, seven cohort studies and 10 case-control studies were included. The pooled relative risks (RRs) of HCC for the highest vs. lowest consumption levels were 1.10 (95% confidence interval, CI: 0.85-1.42) for red meat, 1.01 (95% CI: 0.79-1.28) for processed meat and 0.97 (95% CI: 0.85-1.11) for total meat. Moreover, white meat and fish consumption were found to be inversely associated with HCC risk, the summary RRs were 0.69 (95% CI: 0.58-0.81) and 0.78 (95% CI: 0.67-0.90) respectively, and the results remained quite stable after stratification by the confounding factors.

CONCLUSIONS

The present meta-analysis indicates that a high level of white meat or fish consumption can reduce the risk of HCC significantly, while intake of red meat, processed meat or total meat is not associated with HCC risk. Our findings suggest that dietary intervention may be a promising approach for prevention of HCC, which still need to be confirmed by further well-designed prospective studies and experimental research.

Meat consumption and risk of oral cavity and oropharynx cancer: a meta-analysis of observational studies

PURPOSE

High meat consumption, especially red and processed meat consumption is associated with an increased risk of several cancers, however, evidence for oral cavity and oropharynx cancer is limited. Thus, we performed this meta-analysis to determine the association between intakes of total meat, processed meat, red meat, and white meat, and the risk of oral cavity and oropharynx cancer.

METHODS

Electronic search of Pubmed, Embase, and Cochrane Library Central database was conducted to select relevant studies. Fixed-effect and random-effect models were used to estimate summary relative risks (RR) and the corresponding 95% confidence intervals (CIs). Potential sources of heterogeneity were detected by meta-regression. Subgroup analyses and sensitivity analysis were also performed.

RESULTS

12 case-control studies and one cohort study were included in the analyses, including 501,730 subjects and 4,104 oral cavity and oropharynx cancer cases. Pooled results indicated that high consumption of total meat, red meat, and white meat were not significantly associated with increased risk of oral cavity and oropharynx cancer (RR = 1.14, 95% CI[0.78-1.68]; RR = 1.05, 95% CI[0.66, 1.66] and RR = 0.81, 95% CI[0.54, 1.22], respectively), while the high consumption of processed meat was significantly associated with a 91% increased risk of oral cavity and oropharynx cancer (RR = 1.91, 95% CI [1.19-3.06]). Sensitivity analysis indicated that no significant variation in combined RR by excluding any of the study, confirming the stability of present results.

CONCLUSIONS

The present meta-analysis suggested that high consumption of processed meat was significantly associated with an increased risk of oral cavity and oropharynx cancer, while there was no significantly association between total meat, red meat or white meat and the risk of oral cavity and oropharynx cancer. More prospective cohort studies are warranted to confirm these associations.

Nucleotide excision repair gene polymorphisms, meat intake and colon cancer risk

PURPOSE

Much of the DNA damage from colon cancer-related carcinogens, including heterocyclic amines (HCA) and polycyclic aromatic hydrocarbons (PAH) from red meat cooked at high temperature, are repaired by the nucleotide excision repair (NER) pathway. Thus, we examined whether NER non-synonymous single nucleotide polymorphisms (nsSNPs) modified the association between red meat intake and colon cancer risk.

METHODS

The study consists of 244 African-American and 311 white colon cancer cases and population-based controls (331 African Americans and 544 whites) recruited from 33 counties in North Carolina from 1996 to 2000. Information collected by food frequency questionnaire on meat intake and preparation methods were used to estimate HCA and benzo(a)pyrene (BaP, a PAH) intake. We tested 7 nsSNPs in 5 NER genes: XPC A499V and K939Q, XPD D312N and K751Q, XPF R415Q, XPG D1104H, and RAD23B A249V. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated using unconditional logistic regression.

RESULTS

Among African Americans, we observed a statistically significant positive association between colon cancer risk and XPC 499 AV+VV genotype (OR=1.7, 95% CI: 1.1, 2.7, AA as referent), and an inverse association with XPC 939 QQ (OR=0.3, 95%CI: 0.2, 0.8, KK as referent). These associations were not observed among whites. For both races combined, there was interaction between the XPC 939 genotype, well-done red meat intake and colon cancer risk (OR=1.5, 95% CI=1.0, 2.2 for high well-done red meat and KK genotype as compared to low well-done red meat and KK genotype, pinteraction=0.05).

CONCLUSIONS

Our data suggest that NER nsSNPs are associated with colon cancer risk and may modify the association between well-done red meat intake and colon cancer risk.

Red meat and processed meat consumption and all-cause mortality: a meta-analysis

High consumption of red meat and processed meat has been associated with increased risk of several chronic diseases. We conducted a meta-analysis to summarize the evidence from prospective studies on red meat and processed meat consumption in relationship to all-cause mortality. Pertinent studies were identified by searching PubMed through May 2013 and by reviewing the reference lists of retrieved articles. Prospective studies that reported relative risks with 95% confidence intervals for the association of red meat or processed meat consumption with all-cause mortality were eligible. Study-specific results were combined by using a random-effects model. Nine prospective studies were included in the meta-analysis. The summary relative risks of all-cause mortality for the highest versus the lowest category of consumption were 1.10 (95% confidence interval (CI): 0.98, 1.22; n = 6 studies) for unprocessed red meat, 1.23 (95% CI: 1.17, 1.28; n = 6 studies) for processed meat, and 1.29 (95% CI: 1.24, 1.35; n = 5 studies) for total red meat. In a dose-response meta-analysis, consumption of processed meat and total red meat, but not unprocessed red meat, was statistically significantly positively associated with all-cause mortality in a nonlinear fashion. These results indicate that high consumption of red meat, especially processed meat, may increase all-cause mortality.

Diet and supplements and their impact on colorectal cancer

BACKGROUND

Colorectal cancer is the third commonest cancer and the third leading cause of cancer death among men and women. It has been proposed that dietary factors are responsible for 70-90% of colorectal cancer and diet optimization may prevent most cases.

AIM

To evaluate the role of dietary components and supplements in colorectal cancer.

METHODS

Bibliographical searches were performed in Pubmed for the terms "diet and colorectal cancer", "diet and colon cancer", "diet and rectal cancer", "nutrition and colorectal cancer", "probiotics and colorectal cancer", "prebiotics and colorectal cancer", "alcohol and cancer" and "colorectal cancer epidemiology".

RESULTS

Consumption of processed or red meat, especially when cooked at high temperatures may be associated with increased risk of colorectal cancer. The evidence for dietary fibre is unclear but foods that contain high amounts of fibre are usually rich in polyphenols which have been shown to alter molecular processes that can encourage colorectal carcinogenesis. Meta-analyses provide evidence on the benefits of circulating, diet-derived and supplemented, vitamin D and Calcium. We also found that diets rich in Folate may prevent colorectal carcinoma. The evidence on dietary micronutrients such as Zinc and Selenium in association with colorectal cancer is not conclusive. It has been suggested that there may be a direct association between alcohol intake and colorectal cancer. In vitro and in vivo studies have highlighted a possible protective role of prebiotics and probiotics.

CONCLUSIONS

The lack of randomized trials and the presence of confounding factors including smoking, physical activity, obesity and diabetes may often yield inconclusive results. Carefully designed randomized trials are recommended.

Influence of dietary fat type on benzo(a)pyrene [B(a)P] biotransformation in a B(a)P-induced mouse model of colon cancer

In the US alone, around 60,000 lives/year are lost due to colon cancer. Diet and environment have been implicated in the development of sporadic colon tumors. The objective of this study was to determine how dietary fat potentiates the development of colon tumors through altered B(a)P biotransformation, using the Adenomatous polyposis coli with Multiple intestinal neoplasia mouse model. Benzo(a)pyrene was administered to mice through tricaprylin, and unsaturated (USF; peanut oil) and saturated (SF; coconut oil) fats at doses of 50 and 100 μg/kg via oral gavage over a 60-day period. Blood, colon, and liver were collected at the end of exposure period. The expression of B(a)P biotransformation enzymes [cytochrome P450 (CYP)1A1, CYP1B1 and glutathione-S-transferase] in liver and colon were assayed at the level of protein, mRNA and activities. Plasma and tissue samples were analyzed by reverse phase high-performance liquid chromatography for B(a)P metabolites. Additionally, DNA isolated from colon and liver tissues was analyzed for B(a)P-induced DNA adducts by the (32)P-postlabeling method using a thin-layer chromatography system. Benzo(a)pyrene exposure through dietary fat altered its metabolic fate in a dose-dependent manner, with 100 μg/kg dose group registering an elevated expression of B(a)P biotransformation enzymes, and greater concentration of B(a)P metabolites, compared to the 50 μg/kg dose group (P<.05). This effect was more pronounced for SF group compared to USF group (P<.05). These findings establish that SF causes sustained induction of B(a)P biotransformation enzymes and extensive metabolism of this toxicant. As a consequence, B(a)P metabolites were generated to a greater extent in colon and liver, whose concentrations also registered a dose-dependent increase. These metabolites were found to bind with DNA and form B(a)P-DNA adducts, which may have contributed to colon tumors in a subchronic exposure regimen.

Development of a liquid chromatography/tandem mass spectrometry method to investigate the presence of biomarkers of DNA damage in urine related to red meat consumption and risk of colorectal cancer

RATIONALE

The consumption of red meat is known to enhance the endogenous formation of N-nitroso compounds (NOCs), which are potent carcinogens. DNA damage related to NOCs, and hence red meat, has been detected in colorectal cells and in blood. We proposed to extend previous studies to a non-invasive approach for the detection of O(6)-carboxymethylguanine (O(6)CMG) and O(6)-carboxymethyl-2'-deoxyguanosine (O(6)CMdG) in urine in relation to red meat intake using liquid chromatography/tandem mass spectrometry (LC/MS/MS). The presence of the adduct in urine samples either as the free base or as 2'-deoxynucleoside could help in determining the repair mechanism involved when such lesions are produced. A non-invasive assessment of DNA adducts could also allow for large-scale analyses in the population and cancer prevention dietary strategies.

METHODS

An LC/MS/MS method for the quantitation of O(6)CMG and O(6)CMdG was developed. Urine samples collected from healthy volunteers on red meat and vegetarian diets were analysed either by direct injection or after purification by solid-phase extraction (SPE). A separate LC/MS/MS method for O(6)-methylguanine (O(6)MeG) and O(6)-methyl-2'-deoxyguanosine (O(6)MedG), which are possible hydrolysis products forming during the sample pre-treatment, was also developed.

RESULTS

The developed LC/MS/MS method allowed the simultaneous measurement of O(6)CMG and O(6)CMdG. The limits of detection (LODs) were 0.38 ng/mL for O(6)CMG and 0.18 ng/mL for O(6)CMdG. The direct injection analysis of the clinical samples showed low sensitivity due to high background signal that was improved by SPE purification. However, the concentrations of the adducts in clinical samples were still found to be below the LOD.

CONCLUSIONS

Novel, reproducible, and accurate LC/MS/MS methods were developed for the determination of the urinary content of O(6)CMG and O(6)CMdG, and of the possible formation of O(6)MeG and O(6)MedG by decarboxylation. Clinical samples from volunteers on different diets were analysed. Further studies are required to discover a link between the presence of these biomarkers in urine and red meat consumption.

Red meat-derived heterocyclic amines increase risk of colon cancer: a population-based case-control study

Formation of mutagenic heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) is one pathway believed to drive the association of colon cancer with meat consumption. Limited data exist on the associations of individual HCAs and PAHs in red or white meat with colon cancer. Analyzing data from a validated meat preparation questionnaire completed by 1062 incident colon cancer cases and 1645 population controls from an ongoing case-control study, risks of colon cancer were estimated using unconditional logistic regression models, comparing the fourth to the first quartile of mutagen estimates derived from a CHARRED based food frequency questionnaire. Total dietary intake of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) [adjusted odds ratio (aOR) = 1.87, 95% confidence interval (CI) = 1.44-2.44, P(trend) < 0.0001], 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) (aOR = 1.68, 95% CI = 1.29-2.17, P(trend) = 0.001) and meat-derived mutagenic activity (aOR = 1.77, 95% CI = 1.36-2.30, P(trend) < 0.0001) were statistically significantly associated with colon cancer risk. Meat type specific analyses revealed statistically significant associations for red meat-derived MeIQx, DiMeIQx, and mutagenic activity but not for the same mutagens derived from white meat. Our study adds evidence supporting red meat-derived, but not white-meat derived HCAs and PAHs, as an important pathway for environmental colon cancer carcinogenesis.

Red meat and cancer risk in a network of case-control studies focusing on cooking practices

BACKGROUND

Consumption of red meat has been related to increased risk of several cancers. Cooking methods could modify the magnitude of this association, as production of chemicals depends on the temperature and duration of cooking.

METHODS

We analyzed data from a network of case-control studies conducted in Italy and Switzerland between 1991 and 2009. The studies included 1465 oral and pharyngeal, 198 nasopharyngeal, 851 laryngeal, 505 esophageal, 230 stomach, 1463 colon, 927 rectal, 326 pancreatic, 3034 breast, 454 endometrial, 1031 ovarian, 1294 prostate and 767 renal cancer cases. Controls included 11 656 patients admitted for acute, non-neoplastic conditions. Odds ratios (ORs) and confidence intervals (CIs) were estimated by multiple logistic regression models, adjusted for known confounding factors.

RESULTS

Daily intake of red meat was significantly associated with the risk of cancer of the oral cavity and pharynx (OR for increase of 50 g/day = 1.38; 95% CI: 1.26-1.52), nasopharynx (OR = 1.29; 95% CI: 1.04-1.60), larynx (OR = 1.46; 95% CI: 1.30-1.64), esophagus (OR = 1.46; 95% CI: 1.23-1.72), colon (OR = 1.17; 95% CI: 1.08-1.26), rectum (OR = 1.22; 95% CI:1.11-1.33), pancreas (OR = 1.51; 95% CI: 1.25-1.82), breast (OR = 1.12; 95% CI: 1.04-1.19), endometrium (OR = 1.30; 95% CI: 1.10-1.55) and ovary (OR = 1.29; 95% CI: 1.16-1.43). Fried meat was associated with a higher risk of cancer of oral cavity and pharynx (OR = 2.80; 95% CI: 2.02-3.89) and esophagus (OR = 4.52; 95% CI: 2.50-8.18). Risk of prostate cancer increased for meat cooked by roasting/grilling (OR = 1.31; 95% CI: 1.12-1.54). No heterogeneity according to cooking methods emerged for other cancers. Nonetheless, significant associations with boiled/stewed meat also emerged for cancer of the nasopharynx (OR = 1.97; 95% CI: 1.30-3.00) and stomach (OR = 1.86; 95% CI: 1.20-2.87).

CONCLUSIONS

Our analysis confirmed red meat consumption as a risk factor for several cancer sites, with a limited impact of cooking methods. These findings, thus, call for a limitation of its consumption in populations of Western countries.

Polymorphisms in xenobiotic metabolizing genes, intakes of heterocyclic amines and red meat, and postmenopausal breast cancer

Heterocyclic amines (HCAs) are mutagenic compounds generated when meats are cooked at high temperature and for long duration. The findings from previous studies on the relation between HCAs and breast cancer are inconsistent, possibly because of genetic variations in the enzymes metabolizing HCAs. To evaluate whether the associations of intakes of estimated HCAs, meat-derived mutagenicity (MDM), and red meat with risk of postmenopausal breast cancer were modified by N-acetyltransferase 2 (NAT2) acetylator genotype or cytochrome P450 1A2-164 A/C (CYP1A2) polymorphism, we conducted a nested case-control study with 579 cases and 981 controls within a prospective cohort, the Nurses' Health Study. HCAs and MDM intakes were derived using a cooking method questionnaire administered in 1996. NAT2acetylator genotype, the CYP1A2 polymorphism, and intakes of HCAs, MDM, and red meat were not associated with risk of postmenopausal breast cancer. There was also no interaction between NAT2 acetylator genotype or CYP1A2 polymorphism and HCAs and MDM and red meat intake in relation to breast cancer. These results do not support the hypothesis that genetic polymorphisms of xenobiotic enzymes involved in the metabolism of HCAs may modify the associations between intakes of red meat or meat-related mutagens and breast cancer risk.

Meat intake and cause-specific mortality: a pooled analysis of Asian prospective cohort studies

BACKGROUND

Total or red meat intake has been shown to be associated with a higher risk of mortality in Western populations, but little is known of the risks in Asian populations.

OBJECTIVE

We examined temporal trends in meat consumption and associations between meat intake and all-cause and cause-specific mortality in Asia.

DESIGN

We used ecological data from the United Nations to compare country-specific meat consumption. Separately, 8 Asian prospective cohort studies in Bangladesh, China, Japan, Korea, and Taiwan consisting of 112,310 men and 184,411 women were followed for 6.6 to 15.6 y with 24,283 all-cause, 9558 cancer, and 6373 cardiovascular disease (CVD) deaths. We estimated the study-specific HRs and 95% CIs by using a Cox regression model and pooled them by using a random-effects model.

RESULTS

Red meat consumption was substantially lower in the Asian countries than in the United States. Fish and seafood consumption was higher in Japan and Korea than in the United States. Our pooled analysis found no association between intake of total meat (red meat, poultry, and fish/seafood) and risks of all-cause, CVD, or cancer mortality among men and women; HRs (95% CIs) for all-cause mortality from a comparison of the highest with the lowest quartile were 1.02 (0.91, 1.15) in men and 0.93 (0.86, 1.01) in women.

CONCLUSIONS

Ecological data indicate an increase in meat intake in Asian countries; however, our pooled analysis did not provide evidence of a higher risk of mortality for total meat intake and provided evidence of an inverse association with red meat, poultry, and fish/seafood. Red meat intake was inversely associated with CVD mortality in men and with cancer mortality in women in Asian countries.

A potential role of probiotics in colorectal cancer prevention: review of possible mechanisms of action

A number of investigations, mainly using in vitro and animal models, have demonstrated a wide range of possible mechanisms, by which probiotics may play a role in colorectal cancer (CRC) prevention. In this context, the most well studied probiotics are certain strains from the genera of lactobacilli and bifidobacteria. The reported anti-CRC mechanisms of probiotics encompass intraluminal, systemic, and direct effects on intestinal mucosa. Intraluminal effects detailed in this review include competitive exclusion of pathogenic intestinal flora, alteration of intestinal microflora enzyme activity, reduction of carcinogenic secondary bile acids, binding of carcinogens and mutagens, and increasing short chain fatty acids production. Reduction of DNA damage and suppression of aberrant crypt foci formation have been well demonstrated as direct anti-CRC effects of probiotics on intestinal mucosa. Existing evidence clearly support a multifaceted immunomodulatory role of probiotics in CRC, particularly its ability to modulate intestinal inflammation, a well known risk factor for CRC. The effectiveness of probiotics in CRC prevention is dependent on the strain of the microorganism, while viability may not be a prerequisite for certain probiotic anticancer mechanisms, as indicated by several studies. Emerging data suggest synbiotic as a more effective approach than either prebiotics or probiotics alone. More in vivo especially human studies are warranted to further elucidate and confirm the potential role of probiotics (viable and non-viable), prebiotics and synbiotics in CRC chemoprevention.

Cooking methods and esophageal squamous cell carcinoma in high-risk areas of Iran

Cooking methods have been implicated in the etiology of gastrointestinal cancers, reflecting exposure to potential carcinogens as results of cooking. We used a validated food frequency questionnaire and a pretested cooking method questionnaire in 3 groups: 40 esophageal squamous cell carcinoma (ESCC) cases from a high-risk area in northeast of Iran, 40 healthy subjects from the same high-risk area, and 40 healthy subjects from a low-risk area in Southern Iran. We compared the frequency of boiling, grilling, and frying, and the frying score among these 3 groups. We also calculated "frying index" by multiplying the frequency of each fried food item by its frying score. Mean frying to boiling ratios were 18.2:1, 12.8:1, and 2.6:1 for cases, high-risk controls, and low-risk controls, respectively (P < 0.01). Reuse of cooking oil for frying was reported in 37.5% of the ESCC cases, 25% of high-risk controls, and 7.5% of low-risk controls (P < 0.001). Frying index was higher in the high-risk than in the low-risk controls (P < 0.001) and in cases than in the high-risk controls (P < 0.05) after adjusting for smoking, opium use, rural residence, education, and ethnicity. High-temperature cooking and frying may be associated with increased risk of ESCC in high-risk areas.

Dietary heme iron and the risk of colorectal cancer with specific mutations in KRAS and APC

Red meat intake has been linked to increased colorectal cancer (CRC) risk. Although the underlying mechanisms remain unclear, experimental studies suggest a role for dietary heme iron. Because heme iron was shown to promote specific mutations, it would be insightful to link heme iron data to CRC with mutations in key genes in an observational, population-based study. We investigated the association between dietary heme iron intake and risk of CRC with mutations in APC (adenomatous polyposis coli) and KRAS (Kirsten ras) and P53 overexpression in the Netherlands Cohort Study. After 7.3 years of follow-up, excluding the first 2.3 years due to incomplete coverage of the pathology registry and to avoid preclinical disease, adjusted hazard ratios (including adjustment for total meat) and 95% confidence intervals were calculated, using 4026 subcohort members (aged 55-69 years at baseline), 435 colon and 140 rectal cancer patients. When comparing the highest with the lowest tertile of intake, heme iron intake was associated with an increased risk of CRC harboring activating mutations in KRAS (hazard ratio = 1.71, 95% confidence interval: 1.15-2.57; P for trend = 0.03) and CRC without truncating mutations in APC (hazard ratio = 1.79, 95% confidence interval: 1.23-2.60; P for trend = 0.003). We observed a positive association between heme iron intake and the risk of CRC with activating G>A mutations in KRAS (P for trend = 0.01) and overall G>A mutations in APC (P for trend = 0.005). No associations were found with CRC harboring G>T mutations in KRAS/APC. Heme iron intake was positively associated with the risk of P53 overexpressed tumors but not with tumors without P53 overexpression (Pheterogeneity = 0.12). Heme iron intake was associated with an increased risk of colorectal tumors harboring G>A transitions in KRAS and APC and overexpression of P53. These novel findings suggest that alkylating rather than oxidative DNA-damaging mechanisms are involved in heme-induced colorectal carcinogenesis.

quantitative assessment of the influence of cytochrome P450 1A2 gene polymorphism and colorectal cancer risk

Cytochrome P450 1A2 (CYP1A2) encodes a member of the cytochrome P450 superfamily of enzymes, which play a central role in activating and detoxifying many carcinogens and endogenous compounds thought to be involved in the development of colorectal cancer (CRC). The CYP1A2*C (rs2069514) and CYP1A2*F (rs762551) polymorphism are two of the most commonly studied polymorphisms of the gene for their association with risk of CRC, but the results are conflicting. To derive a more precise estimation of the relationship between CYP1A2 and genetic risk of CRC, we performed a comprehensive meta-analysis which included 7088 cases and 7568 controls from 12 published case-control studies. In a combined analysis, the summary per-allele odds ratio for CRC was 0.91 (95% CI: 0.83-1.00, P = 0.04), and 0.91 (95% CI: 0.68-1.22, P = 0.53), for CYP1A2 *F and *C allele, respectively. In the subgroup analysis by ethnicity, significant associations were found in Asians for CYP1A2*F and CYP1A2*C, while no significant associations were detected among Caucasian populations. Similar results were also observed using dominant genetic model. Potential sources of heterogeneity were explored by subgroup analysis and meta-regression. No significant heterogeneity was detected in most of comparisons. This meta-analysis suggests that the CYP1A2 *F and *C polymorphism is a protective factor against CRC among Asians.

Peptic digestion of beef myofibrils is modified by prior marination

Background

Preparatory steps such as seasoning, marination, and cooking may induce changes in meat which affects the ability of the stomach to adequately digest it. This may result in peptide chains reaching the colon intact where resident bacteria ferment them resulting in the formation of putative carcinogenic phenolic by-products.

Objective

In this study, we set out to determine whether peptic digestion of beef myofibrils was influenced by prior marination.

Design

Cubes of sirloin stewing steak were marinated in balsamic vinegar or left untreated at 4°C overnight. Samples were oven cooked and myofibrils were extracted. Myofibrils were subject to proteolytic digestion with pepsin and digestion products analysed spectrophotometrically and with gel electrophoresis.

Results

Both marination in balsamic vinegar and cooking significantly reduced the yield of myofibrils from shop-purchased beef (P<0.05). Digestion progressed in all samples as a function of time (P<0.01), varying depending on prior treatment. Marination induced resistance to the digestive effect of pepsin during the early to mid-phase of digestion, and we identified a protein band of ∼150 kDa which was protected from peptic digestion in samples which had been marinated and cooked, but not in any other groups.

Conclusions

Pre-treatment of meat prior to cooking may influence specific peptides such that they become more resistant to the digestive actions of pepsin.

Probiotics in colorectal cancer (CRC) with emphasis on mechanisms of action and current perspectives

Colorectal cancer (CRC) is the third most common form of cancer. Diverse therapies such as chemotherapy, immunotherapy and radiation have shown beneficial effects, but are limited because of their safety and toxicity. Probiotic formulations have shown great promise in CRC as preventive and early stage therapeutics. This review highlights the importance of a balanced intestinal microbiota and summarizes the recent developments in probiotics for treating CRC. Specifically, this report describes evidence of the role of probiotics in modulating the microbiota, in improving the physico-chemical conditions of the gut and in reducing oxidative stress. It also discusses the mechanisms of probiotics in inhibiting tumour progression, in producing anticancer compounds and in modulating the host immune response. Even though some of these effects were observed in several clinical trials, when probiotic formulations were used as a supplement to CRC therapies, the application of probiotics as biotherapeutics against CRC still needs further investigation.

Associations between red meat and risks for colon and rectal cancer depend on the type of red meat consumed

Cancer prevention guidelines recommend limiting intake of red meat and avoiding processed meat; however, few studies have been conducted on the effects of specific red meat subtypes on colon cancer or rectal cancer risk. The study aim was to evaluate associations between intake of red meat and its subtypes, processed meat, fish, and poultry and risk for colon cancer or rectal cancer in the Danish Diet, Cancer and Health cohort study. We also evaluated whether fish or poultry should replace red meat intake to prevent colon cancer or rectal cancer. During follow-up (13.4 y), 644 cases of colon cancer and 345 cases of rectal cancer occurred among 53,988 participants. Cox proportional hazards models were used to compute incidence rate ratio (IRRs) and 95% CIs. No associations were found between intake of red meat, processed meat, fish, or poultry and risk for colon cancer or rectal cancer. The risk associated with specific red meat subtypes depended on the animal of origin and cancer subsite; thus, the risk for colon cancer was significantly elevated for higher intake of lamb [IRR(per 5g/d) = 1.07 (95% CI: 1.02-1.13)], whereas the risk for rectal cancer was elevated for higher intake of pork [IRR(per 25g/d) = 1.18 (95% CI: 1.02-1.36)]. Substitution of fish for red meat was associated with a significantly lower risk for colon cancer [IRR(per 25g/d) = 0.89 (95% CI: 0.80-0.99)] but not rectal cancer. Substitution of poultry for red meat did not reduce either risk. This study suggests that the risks for colon cancer and potentially for rectal cancer differ according to the specific red meat subtype consumed.

Meat intake, cooking methods and risk of proximal colon, distal colon and rectal cancer: the Norwegian Women and Cancer (NOWAC) cohort study

Red and processed meat intake is an established risk factor for colorectal cancer (CRC), but epidemiological evidence by subsite and sex is still limited. In the population-based Norwegian Women and Cancer cohort, we examined associations of meat intake with incident proximal colon, distal colon and rectal cancer, in 84,538 women who completed a validated food frequency questionnaire (FFQ) during 1996-1998 or 2003-2005 (baseline or exposure update) at age 41-70 years, with follow-up by register linkages through 2009. We also examined the effect of meat cooking methods in a subsample (n = 43,636). Multivariable hazard ratios (HRs) were estimated by Cox regression. There were 459 colon (242 proximal and 167 distal), and 215 rectal cancer cases with follow-up ≥ 1 (median 11.1) year. Processed meat intake ≥60 vs. <15 g/day was associated with significantly increased cancer risk in all subsites with HRs (95% confidence interval, CI) of 1.69 (1.05-2.72) for proximal colon, 2.13 (1.18-3.83) for distal colon and 1.71 (1.02-2.85) for rectal cancer. Regression calibration of continuous effects based on repeated 24-hr dietary recalls, indicated attenuation due to measurement errors in FFQ data, but corrected HRs were not statistically significant due to wider CIs. Our study did not support an association between CRC risk and intake of red meat, chicken, or meat cooking methods, but a high processed meat intake was associated with increased risk of proximal colon, distal colon and rectal cancer. The effect of processed meat was mainly driven by the intake of sausages.

Combined genotoxic effects of a polycyclic aromatic hydrocarbon (B(a)P) and an heterocyclic amine (PhIP) in relation to colorectal carcinogenesis

Colorectal neoplasia is the third most common cancer worldwide. Environmental factors such as diet are known to be involved in the etiology of this cancer. Several epidemiological studies have suggested that specific neo-formed mutagenic compounds related to meat consumption are an underlying factor involved in the association between diet and colorectal cancer. Heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) are known mutagens and possible human carcinogens formed at the same time in meat during cooking processes. We studied the genotoxicity of the model PAH benzo(a)pyrene (B(a)P) and HCA 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), alone or in mixture, using the mouse intestinal cell line Apc^Min/+, mimicking the early step of colorectal carcinogenesis, and control Apc^+/+ cells. The genotoxicity of B(a)P and PhIP was investigated using both cell lines, through the quantification of B(a)P and PhIP derived DNA adducts, as well as the use of a genotoxic assay based on histone H2AX phosphorylation quantification. Our results demonstrate that heterozygous Apc mutated cells are more effective to metabolize B(a)P. We also established in different experiments that PhIP and B(a)P were more genotoxic on Apc^Min/+ cells compared to Apc^+/+. Moreover when tested in mixture, we observed a combined genotoxicity of B(a)P and PhIP on the two cell lines, with an increase of PhIP derived DNA adducts in the presence of B(a)P. Because of their genotoxic effects observed on heterozygous Apc mutated cells and their possible combined genotoxic effects, both B(a)P and PhIP, taken together, could be implicated in the observed association between meat consumption and colorectal cancer.

Consumption of red and processed meat and esophageal cancer risk: Meta-analysis

To summarize the evidence about the association between red and processed meat intake and the risk of esophageal cancer, we systematically searched the PubMed and EMBASE databases up to May 2012, with a restriction to English publications, and the references of the retrieved articles. We combined the study-specific relative risks (RRs) and 95%CI, comparing the highest with the lowest categories of consumption by using a random-effects model. A total of 4 cohort studies and 23 case-control studies were included in the meta-analysis. The combined RRs (95%CI) of the cohort studies comparing the highest and lowest categories were 1.26 (1.00-1.59) for red meat and 1.25 (0.83-1.86) for processed meat. For the case-control studies, the combined RRs (95%CI) comparing the highest and lowest categories were 1.44 (1.16-1.80) for red meat and 1.36 (1.07-1.74) for processed meat. Findings from this meta-analysis suggest that a higher consumption of red meat was associated with a greater risk of esophageal cancer.

Meat-related compounds and colorectal cancer risk by anatomical subsite

Since meat may be involved in the etiology of colorectal cancer, associations between meat-related compounds were examined to elucidate underlying mechanisms in a population-based case-control study. Participants (989 cases/1,033 healthy controls) completed a food frequency questionnaire with a meat-specific module. Multivariable logistic regression was used to examine associations between meat variables and colorectal cancer; polytomous logistic regression was used for subsite-specific analyses. The following significant positive associations were observed for meat-related compounds: 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) and colorectal, distal colon, and rectal tumors; 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and colorectal and colon cancer tumors; nitrites/nitrates and proximal colon cancer; 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and rectal cancer; and benzo[a]pyrene and rectal cancer (P-trends < 0.05). For analyses by meat type, cooking method, and doneness preference, positive associations between red processed meat and proximal colon cancer and pan-fried red meat and colorectal cancer were found (P-trends < 0.05). Inverse associations were observed between unprocessed poultry and colorectal, colon, proximal colon, and rectal tumors; grilled/barbequed poultry and proximal colon cancer; and well-done/charred poultry and colorectal, colon, and proximal colon tumors (P-trends < 0.05). HCAs, PAHs, nitrites, and nitrates may be involved in colorectal cancer etiology. Further examination into the unexpected inverse associations between poultry and colorectal cancer is warranted.

Dietary patterns and colorectal cancer recurrence and survival: a cohort study

OBJECTIVE

To examine the association between dietary patterns and colorectal cancer (CRC) survival.

DESIGN

Cohort study.

SETTING

A familial CRC registry in Newfoundland.

PARTICIPANTS

529 newly diagnosed CRC patients from Newfoundland. They were recruited from 1999 to 2003 and followed up until April 2010.

OUTCOME MEASURE

Participants reported their dietary intake using a food frequency questionnaire. Dietary patterns were identified with factor analysis. Multivariable Cox proportional hazards models were employed to estimate HR and 95% CI for association of dietary patterns with CRC recurrence and death from all causes, after controlling for covariates.

RESULTS

Disease-free survival (DFS) among CRC patients was significantly worsened among patients with a high processed meat dietary pattern (the highest vs the lowest quartile HR 1.82, 95% CI 1.07 to 3.09). No associations were observed with the prudent vegetable or the high-sugar patterns and DFS. The association between the processed meat pattern and DFS was restricted to patients diagnosed with colon cancer (the highest vs the lowest quartile: HR 2.29, 95% CI 1.19 to 4.40) whereas the relationship between overall survival (OS) and this pattern was observed among patients with colon cancer only (the highest vs the lowest quartile: HR 2.13, 95% CI 1.03 to 4.43). Potential effect modification was noted for sex (p value for interaction 0.04, HR 3.85 for women and 1.22 for men).

CONCLUSIONS

The processed meat dietary pattern prior to diagnosis is associated with higher risk of tumour recurrence, metastasis and death among patients with CRC.

Meat consumption and risk of lung cancer: evidence from observational studies

BACKGROUND

A number of epidemiological studies have reported inconsistent findings on the association between meat consumption and lung cancer.

DESIGN

We therefore conducted a systematic review and meta-analysis to investigate the relationship between meat consumption and lung cancer risk in epidemiological studies.

RESULTS

Twenty-three case-control and 11 cohort studies were included. All studies adjusted for smoking or conducted in never smokers. The summary relative risks (RRs) of lung cancer for the highest versus lowest intake categories were 1.35 (95% confidence interval (CI) 1.08-1.69) for total meat, 1.34 (95% CI 1.18-1.52) for red meat, and 1.06 (95% CI 0.90-1.25) for processed meat. An inverse association was found between poultry intake and lung cancer (RR = 0.91, 95% CI 0.85-0.97), but not for total white meat (RR = 1.06, 95% CI 0.82-1.37) or fish (RR = 1.01, 95% CI 0.96-1.07).

CONCLUSIONS

The relationship between meat intake and lung cancer risk appears to depend on the types of meat consumed. A high intake of red meat may increase the risk of lung cancer by about 35%, while a high intake of poultry decreases the risk by about 10%. More well-designed cohort studies on meat mutagens or heme iron, meat cooking preferences, and doneness level are needed to fully characterize this meat-lung cancer association.

Dietary factors associated with lifetime asthma or hayfever diagnosis in Australian middle-aged and older adults: a cross-sectional study

BACKGROUND

There is abundant research relevant to genetic and environmental influences on asthma and hayfever, but little is known about dietary risk factors in Australian adults. This study's purpose was to identify dietary factors associated with lifetime asthma (AS) and asthma or hayfever (AS/HF) diagnosis in Australian middle-aged and older adults.

METHODS

From The 45 and Up Study baseline self-report data, this study included 156,035 adult men and women. Participants were sampled from the general population of New South Wales, Australia in 2006-2009. About 12% of participants reported ever receiving an AS diagnosis (men 10%; women 14%) and 23% reported AS/HF diagnosis (men 19%; women 26%). Following principle components factor analysis, dietary items loaded onto one of four factors for men (meats/cheese; fruits/vegetables; poultry/seafood; grains/alcohol) or five factors for women (meats; fruits/vegetables; poultry/seafood; cereal/alcohol; brown bread/cheese). Logistic regression was used to analyze the associations between dietary factors and AS or AS/HF diagnosis.

RESULTS

For men, the meats/cheese factor was positively associated with AS (AOR = adjusted odds ratio for highest versus lowest quintile = 1.18, 95%CI = 1.08, 1.28; P(trend) = 0.001) and AS/HF (AOR for highest versus lowest quintile = 1.22, 95%CI = 1.14, 1.29; P(trend) < 0.001). Poultry/seafood was also associated with AS/HF in men (AOR for highest versus lowest quintile = 1.11, 95%CI = 1.04, 1.17; P(trend) = 0.002). For women, significant risk factors for AS/HF included meats (AOR for highest versus lowest quintile = 1.25, 95%CI = 1.19, 1.31; P(trend) = 0.001), poultry/seafood (AOR for highest versus lowest quintile = 1.06, 95%CI = 1.01, 1.12; P(trend) = 0.016), and fruits/vegetables (AOR for highest versus lowest quintile = 1.07, 95%CI = 1.02, 1.12; P(trend) = 0.011). In contrast, the cheese/brown bread dietary factor was protective against AS in women (AOR for highest versus lowest quintile = 0.88, 95%CI = 0.82, 0.94; P(trend) < 0.001).

CONCLUSIONS

Generally, diets marked by greater intakes of meats, poultry, and seafood were associated with diagnosed AS and AS/HF. Taken together, these findings suggest that adherence to a more meat-based diet may pose risk for AS and AS/HF in Australian adults.

Genetic variants in epoxide hydrolases modify the risk of oligozoospermia and asthenospermia in Han-Chinese population

OBJECTIVES

Epoxide hydrolases are involved in detoxifying and excreting the environmental chemicals, which are associated with decreased semen quality and male infertility. We hypothesized that polymorphisms in epoxide hydrolases may be associated with risk of oligozoospermia and asthenospermia.

DESIGN AND METHODS

In this study, 468 fertile controls and 672 idiopathic male infertile patients were recruited. SNPstream and TaqMan assay were used to genotype four single nucleotide polymorphisms in EPHX1 and EPHX2. The semen analysis was performed by computer-assisted semen analysis system.

RESULTS

Our results demonstrated that rs1042064 of EPHX2 was significantly associated with decreased risk of oligozoospermia (OR=0.65, 95% CI: 0.44-0.98) and asthenospermia (OR=0.66, 95% CI: 0.46-0.94).

CONCLUSIONS

Our results provided evidence that genetic variants in epoxide hydrolases may modify the risk of oligozoospermia and asthenospermia in Han-Chinese population.

Diet and nutrient factors in colorectal cancer risk

Diet and nutrition are estimated to explain as much as 30%-50% of the worldwide incidence of colorectal cancer. In 2007, the World Cancer Research Fund (WCRF), in conjunction with the American Institute for Cancer Research (AICR), released the second expert report that summarizes the current scientific evidence linking diet to the prevention of cancer. This text provides an expert summary and level of evidence of the research relating diet/nutrients to factors that influence cancers of multiple organs, including colon and rectum, with an important emphasis on global patterns. Specific examples include dietary fat, red and processed meat, and dairy, as well effects of nutrients such as calcium, folate, and vitamin D. Evidence is obtained from ongoing systematic literature reviews conducted by experts in both the United States and Europe. The expert panel applies standard practices to evaluate the strength and quality of individual studies to draw summary conclusions. In 2011, the report was updated to include findings from a series of meta-analyses published in 2010. To complement the WCRF/AICR report, the authors review the evidence favoring the role for diet and nutrition in the etiology of colorectal cancer. Specifically, they have integrated information gained from more recent meta-analyses and high-quality, prospective study findings, some of which have been included in the 2011 updated WCRF/AICR summary.

[The dietary risk factors for colorectal cancer related to meat consumption]

The integrative review is one of the methodologies used for evidence-based practice which, in this study, had the objective of surveying and synthesizing the evidence available in the literature regarding the dietary risks for colorectal cancer related to the consumption of meat. The search was made using the LILACS, MEDLINE, CINAHL, and COCHRANE Library databases, and six studies considered pertinent to the consumption of meat were found. Meta-analyses showed that there is an association between the consumption of red meat and an increased risk for colorectal cancer from 28% to 35%, whereas processed meats are associated with a rise in risk from 20% to 49%. Evidence shows that the consumption of red meat, processed meat, and total meat consumption are risk factors for developing polyps and colorectal cancer. The search did not yield any studies referring to the consumption of chicken or fish as risk factors.

Meat-related mutagen exposure, xenobiotic metabolizing gene polymorphisms and the risk of advanced colorectal adenoma and cancer

Meat mutagens, including heterocyclic amines (HCAs), polycyclic aromatic hydrocarbons (PAHs) and N-nitroso compounds (NOCs), may be involved in colorectal carcinogenesis depending on their activation or detoxification by phase I and II xenobiotic metabolizing enzymes (XME). Using unconditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI), we examined the intake of five meat mutagens and >300 single nucleotide polymorphisms (SNPs) in 18 XME genes in relation to advanced colorectal adenoma (1205 cases and 1387 controls) and colorectal cancer (370 cases and 401 controls) within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Dietary intake of meat mutagens was assessed using a food frequency questionnaire with a detailed meat-cooking module. An interaction was observed between 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) intake and the NAT1 polymorphism rs6586714 in the adenoma study (P(interaction) = 0.001). Among individuals carrying a GG genotype, high MeIQx intake was associated with a 43% increased risk of adenoma (95% CI 1.11-1.85, P(trend) = 0.07), whereas the reverse was observed among carriers of the A variant (OR = 0.50, 95% CI 0.30-0.84, P(trend) = 0.01). In addition, we observed some suggestive (P < 0.05) modifying effects for SNPs in other XME genes (UGT1A, CYP2E1, EPHX1, AHR and GSTM3), but these were not significant after adjustment for multiple testing. This large and comprehensive study of XME genes, meat mutagens and the risk of colorectal tumours found that a NAT1 polymorphism modified the association between MeIQx intake and colorectal adenoma risk.

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.

Red meat consumption and mortality: results from 2 prospective cohort studies

BACKGROUND

Red meat consumption has been associated with an increased risk of chronic diseases. However, its relationship with mortality remains uncertain.

METHODS

We prospectively observed 37 698 men from the Health Professionals Follow-up Study (1986-2008) and 83 644 women from the Nurses' Health Study (1980-2008) who were free of cardiovascular disease (CVD) and cancer at baseline. Diet was assessed by validated food frequency questionnaires and updated every 4 years.

RESULTS

We documented 23 926 deaths (including 5910 CVD and 9464 cancer deaths) during 2.96 million person-years of follow-up. After multivariate adjustment for major lifestyle and dietary risk factors, the pooled hazard ratio (HR) (95% CI) of total mortality for a 1-serving-per-day increase was 1.13 (1.07-1.20) for unprocessed red meat and 1.20 (1.15-1.24) for processed red meat. The corresponding HRs (95% CIs) were 1.18 (1.13-1.23) and 1.21 (1.13-1.31) for CVD mortality and 1.10 (1.06-1.14) and 1.16 (1.09-1.23) for cancer mortality. We estimated that substitutions of 1 serving per day of other foods (including fish, poultry, nuts, legumes, low-fat dairy, and whole grains) for 1 serving per day of red meat were associated with a 7% to 19% lower mortality risk. We also estimated that 9.3% of deaths in men and 7.6% in women in these cohorts could be prevented at the end of follow-up if all the individuals consumed fewer than 0.5 servings per day (approximately 42 g/d) of red meat.

CONCLUSIONS

Red meat consumption is associated with an increased risk of total, CVD, and cancer mortality. Substitution of other healthy protein sources for red meat is associated with a lower mortality risk.

Investigation of a possible relationship between EPHX1 gene polymorphisms and colorectal cancer in Turkish society

Metabolism of chemical carcinogens, including their activation and detoxification, plays a key role in carcinogenesis. Microsomal epoxide hydrolase (EPHX1) has an important role in the metabolism of polycyclic aromatic hydrocarbons and detoxification of procarcinogens. The aim of this study was to investigate the association between colorectal cancer (CRC) development and EPHX1 gene polymorphisms. We investigated the polymorphisms in exon 3 (T>C, Tyr113His) and exon 4 (A>G, His139Arg) of the EPHX1 gene in 68 CRC patients and 116 controls by polymerase chain reaction-restriction fragment length polymorphism. The frequencies of the Try113Try, Try113His, and His113His for EPHX1 exon 3 were 37.9%, 55.2%, and 6.9% in controls and 39.7%, 42.6%, and 17.6% in CRC patients, respectively. Frequencies of EPHX1 exon 4 genotypes were 62.1% His139His, 37.9% His139Arg, and 0% Arg139Arg in the control group and 76.5% His139His, 22.1% His139Arg, and 1.5% Arg139Arg in the patient group. Individuals carrying the EPHX1 exon 3 His113His genotype had a 2.5-fold increased risk (p=0.024), and those carrying the EPHX1 exon 4 His139Arg genotype had decreased risk of CRC compared with controls (p=0.019). Even though exon 3 Tyr113His and exon 4 His139Arg polymorphisms for EPHX1 gene appear to be important factors for CRC risk, further investigations with larger study groups are needed to fully elucidate the role of these polymorphisms in the development of CRC.

The association of NAT1 polymorphisms and colorectal carcinoma risk: evidence from 20,000 subjects

Published data on the association between N-acetyltransferase 1 (NAT1) gene polymorphisms and colorectal carcinoma (CRC) susceptivity are inconclusive. To derive a more precise estimation of the association, we conducted this meta-analysis. Data were collected from electronic databases: PubMed, EMBASE, with the last report up to May 2010. The odds ratio (OR) and corresponding 95% confidence intervals (CIs) were used to assess the strength of the association. A total of 20 individual studies including 8,219 cases and 11,498 controls based on the search criteria were involved. Meta-analysis was performed for slow versus rapid acetylation genotypes of NAT1. We found no association between NAT1 polymorphisms and CRC in overall population (OR = 0.96, 95% CI = 0.88-1.05 P = 0.05 for heterogeneity) without significant publication bias present. In subgroup analyses, similar results were found in different ethnicities, source of controls, genotyping methods and adjustment. Current meta-analysis suggests that lack of association between the NAT1 polymorphisms and individual risk to CRC.