Mutagens in coffee and tea

Exposure to chemicals formed from natural processes is ubiquitous

Exposure to chemicals produced by natural processes is ubiquitous. First, in addition to the products of normal metabolism produced in humans of normal body weight, adipose tissue produces a large number of chemicals, including estrogen, testosterone from the produced estrogen, thyroid-stimulating hormone, leptin and approximately 500 other molecules termed adipokines, and a large number of inflammatory mediators. Second, the gut biome contains approximately the same number of bacteria as cells found in the entire body and produces a large number of small molecules. Third, the overwhelming majority (99.9%) of pesticide exposure occurs during ingestion of natural plant pesticides from eating vegetables. Fourth, consumption of cooked muscles meats leads to significant exposure to mutagenic and carcinogenic heterocyclic amines, polycyclic aromatic amines, and nitropyrenes. Fifth, many common beverages, for example, beer, coffee, and tea contain organic chemicals that display mutagenic activity. As compared with man-made production levels, from 1945 to 2015, an estimated 5000-fold more organic compounds were produced by a variety of natural processes, including common wood-degrading and forest litter-degrading fungi, microorganisms in temperate and boreal forest soils, bacteria in marine sponges, marine macro-algae, volcanoes, and forest fires. Exposure to these naturally produced organic compounds occurs via inhalation of ambient air, ingestion of food and water, and contact with soil, freshwater, and seawater. Contact with several thousand different endogenous or exogenous chemicals per day is unavoidable. This understanding might assist in better allocating resources toward controlling exposures to agents of highest concern as determined by current concepts of chronic disease causation.

Identification of methylglyoxal as a major mutagen in wood and bamboo pyroligneous acids

To identify the major mutagen in pyroligneous acid (PA), 10 wood and 10 bamboo pyroligneous acids were examined using the Ames test in Salmonella typhimurium strains TA100 and TA98. Subsequently, the mutagenic dicarbonyl compounds (DCs), glyoxal, methylglyoxal (MG), and diacetyl in PA were quantified using high-performance liquid chromatography, and the mutagenic contribution ratios for each DC were calculated relative to the mutagenicity of PA. Eighteen samples were positive for mutagens and showed the strongest mutagenicity in TA100 in the absence of S9 mix. MG had the highest mutagenic contribution ratio, and its presence was strongly correlated with the specific mutagenicity of PA. These data indicate that MG is the major mutagen in PA.

Genome-wide association analysis of coffee drinking suggests association with CYP1A1/CYP1A2 and NRCAM

Coffee consumption is a model for addictive behavior. We performed a meta-analysis of genome-wide association studies (GWASs) on coffee intake from 8 Caucasian cohorts (N=18 176) and sought replication of our top findings in a further 7929 individuals. We also performed a gene expression analysis treating different cell lines with caffeine. Genome-wide significant association was observed for two single-nucleotide polymorphisms (SNPs) in the 15q24 region. The two SNPs rs2470893 and rs2472297 (P-values=1.6 × 10(-11) and 2.7 × 10(-11)), which were also in strong linkage disequilibrium (r(2)=0.7) with each other, lie in the 23-kb long commonly shared 5' flanking region between CYP1A1 and CYP1A2 genes. CYP1A1 was found to be downregulated in lymphoblastoid cell lines treated with caffeine. CYP1A1 is known to metabolize polycyclic aromatic hydrocarbons, which are important constituents of coffee, whereas CYP1A2 is involved in the primary metabolism of caffeine. Significant evidence of association was also detected at rs382140 (P-value=3.9 × 10(-09)) near NRCAM-a gene implicated in vulnerability to addiction, and at another independent hit rs6495122 (P-value=7.1 × 10(-09))-an SNP associated with blood pressure-in the 15q24 region near the gene ULK3, in the meta-analysis of discovery and replication cohorts. Our results from GWASs and expression analysis also strongly implicate CAB39L in coffee drinking. Pathway analysis of differentially expressed genes revealed significantly enriched ubiquitin proteasome (P-value=2.2 × 10(-05)) and Parkinson's disease pathways (P-value=3.6 × 10(-05)).

Screening of non-polar heterocyclic amines in urine by microextraction in packed sorbent-fluorimetric detection and confirmation by capillary liquid chromatography

A rapid and simple procedure for the direct screening of urine samples is described. The method involves microextraction in a packed sorbent (MEPS) that is on-line coupled to a capillary liquid chromatograph with fluorimetric detection. The overall arrangement works as a screening/confirmatory system for monitoring non-polar heterocyclic aromatic amines (HAAs) in urine samples. This configuration allows the selective retention of HAAs from urine on a C(18) MEPS cartridge integrated in the needle of a micro-well plate autosampler. Retained HAAs were eluted with methanol/water (90:10, v/v) and directly injected into the fluorimetric detector. This screening method provides a yes/no binary response that may require confirmation. The samples for which the concentration of HAAs was close to or above the established threshold limit (30 ng mL(-1)) were subjected to capillary liquid chromatography (CLC) for confirmation purposes. A mobile phase of acetonitrile and triethylamine (25 mM) at pH 2.5, through a gradient of composition at a flow rate of 20 μL min(-1), resulted in good separations between the analytes in less than 11 min. This confirmation method allowed the determination of the analytes in the 10-100 ng mL(-1) range for harmane and norharmane and from 20 to 200 ng mL(-1) for 3-amino-1,4-dimethyl-5H-pyrido-[4,3-b] indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido-[4,3-b] indole (Trp-P-2), 2-amino-9H-pyrido-[2,3-b] indole (AαC) and 2-amino-3-methyl-9H-pyrido-[2,3-b] indole (MeAαC), with relative standard deviation (RSD) values between 2.12% and 3.73%, and limits of detection between 1.6 and 5.6 ng mL(-1) for all the HAAs.

A review of the epidemiological evidence on tea, flavonoids, and lung cancer

Tea and its main bioactive ingredients, the flavonoids, have been associated with human cancer for several decades. In this article, an overview is provided of observational epidemiological studies of lung cancer incidence in relation to intake of green tea, black tea, flavonols/flavones, and catechins. A PubMed search was conducted in September 2007. Articles were selected if they provided risk ratios (relative risk or odds ratio) for lung cancer and were of observational design (cohort, case-control, or case-cohort). Three of 12 studies reported a significantly lower risk of lung cancer with a high intake of flavonoids, whereas 1 study reported a significantly increased risk. After stratification by type of flavonoid, catechin intake was no longer associated with lung cancer risk in 3 of 4 studies available. For tea, 4 of 20 studies reported significantly reduced risks with high intake. Two studies found significantly increased risk ratios, but both were older studies. Findings were similar for green and black tea but became more significant when only methodologically sounder cohort studies were considered. When tea intake and lung cancer were studied among never- or former smokers to eliminate the confounding effect of smoking, 4 of 7 reported associations were significantly protective. In general, the studies on tea, flavonoids, and lung cancer risk indicate a small beneficial association, particularly among never-smokers. More well-designed cohort studies, in particular for catechins, are needed to strengthen the evidence on effects of long-term exposure to physiological doses of dietary flavonoids.

Chemistry and genotoxicity of caramelized sucrose

Caramelization of a 1% sucrose solution at 180 degrees C accompanied characteristic changes in pH, Mr, UV-absorbance, and fluorescence values as well as increased reducing power activity after 40-60 min. Similar changes occurred to sucrose heated at 150 degrees C, after 150-240 min. Bioactivity of caramelized sucrose samples was tested for mutagenic activity, using Salmonella typhimurium strains TA-98 and TA-100, respectively, as well as the Saccharomyces D7 yeast strain for mitotic recombination and Chinese hamster ovary cells (CHO) to assess clastogenicity. Caramelized sucrose expressed no mutagenicity in the TA-98 strain, but gave positive (p < 0.05) results with the TA-100, base-pair substitution strain. Similarly, mitotic recombination in the Saccharomyces D7 yeast strain and clastogenic activity in CHO cells were induced when exposed to caramelized sucrose. In the all cases, preincubation with S-9 reduced (p < 0.05) the mutagenic activities of caramelized sucrose. Fractionation of the caramelized sucrose into volatile and nonvolatile compounds was performed and tested for clastogenicity using CHO cells. Volatile components contributed approximately 10% to total clastogenicity, which was enhanced by the presence of S-9. Nonvolatile components recovered, consisting of relatively lower Mr, gave highest (p < 0.05) clastogenic activity, denoting that higher Mr caramel colors are relatively free of this property.

The carcinogenic and protective effects of food

It has been estimated that 70% of all cancers are caused by the food that we consume and smoking tobacco (Wogan et al, 2004). Currently, food health advice focuses on maintaining a diet which is low in fat and calories, rather than concentrating on the cooking methods used and the amount of meat that is consumed. More time should be spent educating individuals on the importance of cooking in different ways and eating a varied diet which includes cruciferous vegetables, such as broccoli. Nurses can be influential in the provision of health education advice to patients on the types of cooking methods that can be used to reduce the risk of developing forms of cancer and also the types of food that offer protection against cancer.

Dietary habits and stomach cancer risk in the JACC Study

BACKGROUND: Despite a declining incidence, stomach cancer is still a dominant cancer in Japan. The association between dietary habits and stomach cancer risk was investigated in a large prospective study in Japan.

METHODS: Data were obtained using a self-administered questionnaire from 1988 through 1990. Food frequency questionnaire was used to evaluate the consumption of 33 selected food items. Proportional hazard model was used to determine the hazard ratios (HRs) and their 95% confidence intervals (CIs) of stomach cancer for different levels of the dietary intakes.

RESULTS: A western style breakfast showed an inverse association with stomach cancer risk in males (HR=0.49, 95% CI: 0.35-0.70). Women who consumed liver three to four times per week and more than once per day had a significant increased risk, respectively (HR=2.02, 95% CI: 1.12-3.63, HR=3.16, 95% CI: 1.16-8.62 ). A clear dose-response relationship between the intake of liver and stomach cancer risk was observed. We found no association between stomach cancer mortality and the consumption of fruit such as mandarin orange, and vegetables such as carrots and spinach in both men and women. The consumption of high salt foods such as miso soup and pickles was also not significantly associated with the mortality of stomach cancer in both sexes.

CONCLUSION: This prospective study suggested that a western-style breakfast is associated with a lower risk of stomach cancer, although some differences in the association were seen between men and women.

EPR study of free radicals in bread

The features of the recorded EPR spectra of paramagnetic species formed in bread and rusk are reported. The appearance of free radicals in them is only connected with their thermal treatment since the starting materials (flour and grains) exhibit very weak EPR signal. The obtained EPR spectra are complex and indicate that: (i) the relative number of paramagnetic species depends on the temperature and treating time of the raw product; (ii) the g-values are strongly temperature dependent with a tendency to coincide at t > or = 220 degrees C. Because of the relatively low (150-220 degrees C) temperature of thermal treatment, the studied free radicals can be assumed to appear in the course of the browning (Maillard) reaction and not to the carbonization of the material.

Total equivalent of reactive chemicals in 142 human food items is highly variable within and between major food groups

Many reactive electrophilic chemicals (e.g., acrylamide and hydrazine) occur in foods, and these could individually or cumulatively contribute to human cancer or other diseases. Glutathione (GSH) reacts with and detoxifies electrophilic compounds and is used physiologically to protect against a broad range of toxic and mutagenic compounds. To elucidate the distribution of reactive chemicals in foods, we added a known amount of GSH to 142 commonly consumed food items and assayed the relative amounts of reactive chemicals in terms of the amount of GSH lost during homogenization and extraction, defined quantitatively in terms of glutathione-reactive units (GRUs). Thirty-four items contained GRUs but no detectable GSH; 53 items contained both GSH and GRUs; 18 items contained no GSH or GRUs; and 37 items contained GSH but no detectable GRUs. Among the food groups, cereals, bread, milk, and milk products had relatively high GRU concentrations and low GSH concentrations; several common beverages also had high GRU concentrations and low GSH concentrations; meats and main course dishes were generally low in GRUs and high in GSH. Fruits and vegetables varied in GRU concentration, but most fresh fruits and vegetables had considerably more GSH than GRUs; exceptions were canned vegetables, which had no GSH or GRUs; fruit drinks, which had moderate levels of GRUs and no GSH; and 3 fruits (blueberries, cherries, and prunes), which had high GRU levels. The results provide a database that can be used with food frequency analyses to evaluate the possible association of health risks with the consumption of foods high in GSH-reactive chemicals.

Consumption of non-alcoholic beverages and prostate cancer risk

Our objective was to investigate the relations between the consumption of coffee, tea and carbonated beverages and the development of prostate cancer. The design was a population-based case-control study set in Montreal. The analysis was restricted to the subset of men, aged 45-70 years, who underwent interviews in which aspects of lifelong consumption of non-alcoholic beverages were ascertained. There were 399 incident cases of prostate cancer, 476 population controls and 621 cancer controls. There was no association between the consumption of either coffee or carbonated beverages and the development of prostate cancer. Among daily tea drinkers, the odds ratio associated with the highest tertile of cumulative consumption was 2.0 (95% confidence interval (CI) 1.3-3.0) when using population controls and 1.6 (95% CI 1.0-2.4) when using cancer controls. In conclusion, the consumption of coffee or carbonated beverages does not influence the risk of prostate cancer. Our findings provide no support to the hypothesis that tea consumption may be protective. While tea consumption may increase prostate cancer risk, we were unable to rule out alternative explanations for the positive association that we observed.

Nutrition and dietary carcinogens

Three major factors for human carcinogenesis are (i) cigarette smoking, (ii) infection and inflammation and (iii) nutrition and dietary factors. Nutrition and dietary factors include two categories, namely genotoxic agents and constituents including tumor promotion-associated phenomena. This article first describes the genotoxic agents as microcomponents. These are mutagens/carcinogens in cooked food, fungal products, plant and mushroom substance, and nitrite-related materials, polycyclic aromatic hydrocarbons and oxidative agents. Emphasis has been given to heterocyclic amines (HCAs) to which humans are continuously exposed in an ordinary lifestyle. HCAs in food are mainly produced from creatin(in)e, sugar and from amino acids in meat (upon heating). They are imidazoquinoline and imidazoquinoxaline derivatives and phenylimidazopyridine. HCAs are pluripotent in producing cancers in various organs including breast, colon and prostate. Discussion is also given to plant flavonoids which are mutagenic but not carcinogenic. As a macrocomponent, overintake of total calories, fat and sodium chloride is discussed from the viewpoint of the increase of genetic alterations in tissues and of tumor promotion-associated issues. Studies of nutrition and dietary condition will eventually lead us to cancer prevention, namely delay of onset of cancer to the late phase of human life, which is called 'natural-end cancer' (Tenju-gann).

Chemopreventive effects of coffee bean and rice constituents on colorectal carcinogenesis

Polyphenolic compound chlorogenic acid (CGA) known to be much contained in coffee beans was found to have a regressive effect on induced aberrant crypt foci (ACF) as well as on development of ACF in azoxymethane (AOM)-induced colorectal carcinogenesis in rats. Rice germ and gamma-aminobutyric acid-enriched defatted rice germ inhibited AOM-induced ACF formation and colorectal carcinogenesis in rats. Ferulic acid (FA) also known to be contained in coffee beans and rice prevented AOM-induced ACF formation and intestinal carcinogenesis in rats. Both of food factors, coffee and rice may be of benefit to prevention of human colorectal cancers.

A new approach to risk estimation of food-borne carcinogens--heterocyclic amines--based on molecular information

Identification of causative agents for human cancers is the goal of our studies. We analyzed ordinary foods for mutagenicity, using the well-established Salmonella test. Heating fish and meat yielded mutagens that require metabolic activation for exhibition of mutagenicity. Structural determination revealed these mutagens to be heterocyclic amines (HCAs), their precursors in some cases being creatin(in)e, sugars and amino acids. Ten HCAs so far examined have all proved carcinogenic in mice and rats, inducing cancers in various organs such as in the mammary glands, prostate, lung, colon, skin, bladder and liver. Human exposure to HCAs is 0.1-12 microg/day, predominantly to 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx). For these types of genotoxic carcinogens, DNA-adduct formation is crucially important and PhIP-DNA adducts have been detected in human tissues. However, the amounts of individual HCAs ingested by humans may not be sufficient to induce cancers by themselves and many environmental factors have also been implicated in neoplasia in man, with other considerable inter-individual variation in susceptibility, e.g., to colon carcinogenesis. This is in line with results obtained by feeding different strains of rats with HCA. Studies using lacI transgenic mice and rats have revealed that DNA adducts do not directly correlate with mutant frequencies at the organ level, or cancer incidence. However, sequencing of the Apc gene of rat colon tumors induced by PhIP revealed that it induces a signature mutation of G deletion from the GGGA sequence. This type of mutation is found in the p53 gene of 0.3% human cancers having p53-somatic mutations, and it has been calculated that 3%-10% of the p53 mutations detected in human cancers could be ascribable to PhIP. Although there remains the possibility that other carcinogens involved in human carcinogenesis cause the same signature mutation, the available data point to an important role for PhIP.

Genotoxicity of instant coffee: possible involvement of phenolic compounds

Instant coffee exhibits direct genotoxic activity in the tester strains TA 98, 100, 102, 104 and YG 1024. In the Ames tester strain TA 100, the presence of S9 mix, S100 mix, S9 mix without cofactors led to a significant decrease of the genotoxicity observed. The decrease observed in the presence of S9 mix seems to be highly correlated with the catalase content of S9 mix. The genotoxicity of instant coffee detected in strain TA 100 was dependent on the pH, with higher genotoxic effects at pH values above neutrality. Also, dependent on the pH was the ability of some phenolic molecules present in coffee promoting the degradation of deoxyribose in the presence of Fe3+/EDTA. These results suggest that apart from other molecules present in instant coffee responsible for their genotoxicity in several short term assays, phenolic molecules could also be implicated in the genotoxicity of coffee, via reactive oxygen species arising from its auto-oxidation.

Identification of hydroxyhydroquinone in coffee as a generator of reactive oxygen species that break DNA single strands

A component in instant coffee that caused DNA single strand breaks was isolated by successive ethyl acetate:ethanol extraction, silica gel column chromatography and high performance liquid chromatography using a reversed phase column. The active component was identified as hydroxyhydroquinone (HHQ). Incubation of supercoiled pBR 322 DNA with HHQ at 0.1 mM in phosphate buffer (pH 7.4) at 37 degreesC for 1 h caused single strand breaks, and reactive oxygen species, hydrogen peroxide and hydroxyl radical, were involved in DNA breaking by HHQ. Genotoxic effects of HHQ including DNA breaking activity through generation of reactive oxygen species have been well-demonstrated because the component is considered to be an important genotoxic intermediate metabolite of benzene. Occurrence of HHQ in coffee must have an important significance to consider genotoxicity of coffee.

Genetic damage induced by methylglyoxal and methylglyoxal plus X-rays in Drosophila melanogaster germinal cells

The effect of methylglyoxal (MG) and MG administered prior to X-irradiation was investigated in Drosophila melanogaster germinal cells using the sex-linked recessive lethal (s.l.r.l.), II-III autosomal translocation (AT) and X-chromosome nondisjunction (ND) tests. For the s.l.r.l. test the males were either injected with MG (0.5 M, 0.75 M or 1.7 M) or fed for 24 h (1 M) and two 24 h broods (A and B) were obtained. For the AT test the males were injected with MG 1.7 M and the same brooding scheme was followed. ND was tested in females fed on MG 1 M. The only effect observed after MG treatment was a significant increase on the yield of s.l.r.l. with MG 1.7 M. In the combined treatments MG was administered prior to irradiation with 20 Gy of X-rays and the induction of s.l.r.l. and AT was assessed. Pre-treatment with MG 0.75 M and 1.7 M enhanced the frequency of s.l.r.l. in cells sampled in brood B, consisting mainly of the rather hypoxic late spermatids. It is suggested that this radiosensitizing effect could be ascribed to a decrease in the level of glutathione due to the metabolization of MG.

Tea and coffee consumption and risk of colon and rectal cancer in middle-aged Finnish men

The association between coffee and black tea consumption and the subsequent risk of colon and rectal cancer was investigated within a Finnish clinical trial cohort. One hundred eleven cases of colon cancer and 83 cases of rectal cancer were diagnosed over a median of 9.0 years of follow-up. Proportional hazards regression models were used to derive adjusted relative risk (RR) and 95% confidence intervals (CI) for the association between coffee and tea consumption and cancer incidence. After controlling for confounders, coffee was not significantly associated with colon or rectal cancer. A positive association was seen for increased consumption of tea drinking and colon cancer. Compared with persons who did not drink tea, those who consumed <1 cup/day had an RR of 1.40 (95% CI = 0.84 - 2.33) and those who consumed > or = 1 cup/day had an RR of 2.09 (95% CI = 1.34-3.26, p for trend = 0.001). In contrast, tea consumption had little effect on rectal cancer incidence. This study does not support the hypothesis that coffee and tea protect against colorectal cancer risk. However, given the strength of the tea-colon cancer association and the significant gradient of risk we observed across level of intake, further epidemiologic research of this relationship in other populations seems warranted.

Modulation of metal-induced genotoxicity by Maillard reaction products isolated from coffee

PM2 bacteriophage DNA was exposed to non-dialysable Maillard reaction products (MRPs) isolated from brewed (Br), boiled (Bo) and instant (I) coffee brew extracts in a Fe2+ catalysed Fenton reaction at four pH conditions (i.e. 7.5, 4.0, 3.2, 2.6). MRPs were incubated with DNA either directly with Fe2+, or following a short preincubation period conducted with Fe2+ in an atmosphere of oxygen or argon. Damage to supercoiled DNA resulting in strand scissions as characterized by both nicked circular and linear forms were found to occur either with coffee MRPs or Fe2+ alone, in a dose-dependent manner at all pH conditions tested. At low MRP concentrations, damage to DNA with respect to Fe2+ was lowered only when MRPs were preincubated with Fe2+ in argon or oxygen before incubating with DNA. The addition of MRPs and Fe2+ to DNA without preincubation, had no effects in protecting DNA damage. This finding showed that a preincubation step is necessary for MRPs to chelate Fe2+ in order to mitigate the Fenton reaction. In contrast, the protective effects against Fe2+-induced DNA breakage by MRPs were lost at high coffee MRP concentrations, irrespective of the incubation method used. Increasingly higher concentrations of MRPs in combination with Fe2+ actually enhanced the breakage of DNA with respect to the control. These results indicate that MRPs at high concentrations do not improve Fe2+ ion chelation, but rather accelerate the DNA breakage by possibly changing the redox state of the transition element.

Lignan and isoflavonoid concentrations in tea and coffee

Tea is a beverage consumed widely throughout the world. The existence in tea of chemopreventing compounds possessing antimutagenic, anticarcinogenic and antioxidative properties has been reported. High intakes of tea and foods containing flavonoids have recently been shown to be negatively correlated to the occurrence of CHD. However, tea may contain other compounds with similar activities. Using a new gas chromatographic-mass spectrometric method we measured lignans and isoflavonoids in samples of twenty commercial teas (black, green and red varieties) and, for comparison, six coffees. Both unbrewed and brewed tea were investigated. The analysis of the teas yielded relatively high levels of the lignans secoisolariciresinol (5.6-28.9 mg/kg; 15.9-81.9 mumol/kg) and matairesinol (0.56-4.13 mg/kg; 1.6-11.5 mumol/kg) but only low levels of isoflavonoids. Because the plant lignans, as well as their mammalian metabolites enterolactone and enterodiol, have antioxidative properties and these mammalian lignans occur in high concentrations in plasma, we hypothesize that lignan polyphenols may contribute to the protective effect of tea on CHD.

32P-Postlabeling analysis of a DNA adduct, an N2-acetyl derivative of guanine, formed in vitro by methylglyoxal and hydrogen peroxide in combination

Methylglyoxal is a direct-acting mutagen in Salmonella typhimurium TA100 and its mutagenicity is markedly enhanced in the presence of hydrogen peroxide. In addition, a mixture of methylglyoxal and hydrogen peroxide reacts with 2'-deoxyguanosine to form N2-acetyl-2'-deoxyguanosine. We examined whether the guanine residues in DNA were acetylated by methylglyoxal in the presence of hydrogen peroxide using the 32P-postlabeling method. First, N2-acetyl-2'-deoxyguanosine 3'-monophosphate and N2-acetyl-2'-deoxyguanosine 3,5'-diphosphate were chemically synthesized as standard compounds for the analysis. Then calf thymus DNA (3.24 micromol) was treated with methylglyoxal (64.8 micromol) at pH 7.4 for 3 h at 37 degrees C, and subsequently with hydrogen peroxide (64.8 micromol) at 37 degrees C for 2 h. The adduct formation was analyzed using HPLC in combination with the 32P-postlabeling method under the standard conditions. N2-Acetyl-2'-deoxyguanosine was detected at levels of 2/10(6) nucleotides in double-stranded DNA and 1/10(5) nucleotides in single-stranded DNA. The estimated limit of detection by our method was 3 per 10(8) nucleotides.

Tea consumption and lung cancer risk: a case-control study in Okinawa, Japan

To disclose the relationship between tea consumption and lung cancer risk, we analyzed the data from a case-control study conducted in Okinawa, Japan from 1988 to 1991. The analysis, based on 333 cases and 666 age-, sex- and residence-matched controls, provided the following major findings. (a) The greater the intake of Okinawa tea (a partially fermented tea), the smaller the risk, particularly in women. For females, the odds ratios (and 95% confidence intervals) for those who consumed 1-4, 5-9, and 10 cups or more of Okinawan tea every day, relative to non-daily tea drinkers, were 0.77 (0.28-2.13), 0.77 (0.26-2.25) and 0.38 (0.12-1.18), respectively (trend: P = 0.032). The corresponding odds ratios for males were 0.85 (0.45-1.55), 0.85 (0.45-1.56) and 0.57 (0.31-1.06) (trend: P = 0.053). (b) The risk reduction by Okinawan tea consumption was detected mainly in squamous cell carcinoma. Daily tea consumption significantly decreased the risk of squamous cell carcinoma in males and females, the odds ratios being 0.50 (95% confidence interval 0.27-0.93) and 0.08 (0.01-0.68), respectively. These findings suggest a protective effect of tea consumption against lung cancer in humans.

Analysis of the potential carcinogenicity of coffee and its related compounds in a medium-term liver bioassay of rats

The potential carcinogenicity of coffee and related compounds was examined using a medium-term liver bioassay based on the induction of glutathione S-transferase placental form (GST-P)-positive foci in F344 rats. A total of 230 males were initially injected with diethylnitrosamine (200 mg/kg body weight, ip) or saline as controls and 2 wk later were fed on diet or drinking water supplemented as follows for 6 wk: 5% regular instant coffee; 5% decaffeinated instant coffee; freshly brewed coffee, 8 g in 140 ml water; 0.1% caffeine, 0.2% methylglyoxal, 0.2% glyoxal; or 0.3% theophylline in the drinking water (w/v); and 0.4% theobromine in the diet (w/w). All rats were subjected to two-thirds partial hepatectomy at wk 3 and killed at wk 8. The resultant values for GST-P-positive hepatic focus induction were slightly increased with methylglyoxal and decreased with glyoxal and theobromine compared with the corresponding controls. Although the increase in number of foci for methylglyoxal was statistically significant at P < 0.05, the value was within the historical control levels. Regular and decaffeinated instant coffee as well as fresh-brewed coffee, caffeine and theophylline exerted no effects on focus development. Thus, the coffee-related compounds examined demonstrated no obvious enhancing potential, and it is therefore concluded that coffee and its main constituents are not carcinogenic for the rat liver.

Role of chemopreventers in human diet

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

Possible occurrence of new mutagens with the DNA breaking activity in coffee

Brewed and instant coffee emitted strong chemiluminescence due to singlet oxygen and excited carbonyls, which may be originated by the Maillard reaction of sugars and amino acids but not by the reaction of polyphenolics. Instant coffee cleaved DNA giving single-strand breaks only after it was purified by high performance liquid chromatography (HPLC) or by gel filtration. Retention times of component(s) with strong DNA breaking activity in HPLC were different from those of chemiluminescence emitters, although they were coeluted on a gel filtration. The major DNA breaking component(s) must be different from chemiluminescence emitters. Active oxygen radicals participated little in DNA breaking because active oxygen radical scavengers had only a marginal effect on DNA breaking of the active gel fraction. DNA breaking by the active gel fraction was inhibited by high concentrations of inorganic salts probably because the salts stabilized the DNA double strands. The active gel fraction was mutagenic to Salmonella typhimurium TA98 without metabolic activation. The number of His+ revertant colonies/g of instant coffee powder was estimated to be 4000.

Potential genotoxic, mutagenic and antimutagenic effects of coffee: a review

Coffee and caffeine are mutagenic to bacteria and fungi, and in high concentrations they are also mutagenic to mammalian cells in culture. However, the mutagenic effects of coffee disappear when bacteria or mammalian cells are cultured in the presence of liver extracts which contain detoxifying enzymes. In vivo, coffee and caffeine are devoid of mutagenic effects. Coffee and caffeine are able to interact with many other mutagens and their effects are synergistic with X-rays, ultraviolet light and some chemical agents. Caffeine seems to potentiate rather than to induce chromosomal aberrations and also to transform sublethal damage of mutagenic agents into lethal damage. Conversely, coffee and caffeine are also able to inhibit the mutagenic effects of numerous chemicals. These antimutagenic effects depend on the time of administration of coffee as compared to the acting time of the mutagenic agent. In that case, caffeine seems to be able to restore the normal cycle of mitosis and phosphorylation in irradiated cells. Finally, the potential genotoxic and mutagenic effects of the most important constituents of coffee are reviewed. Mutagenicity of caffeine is mainly attributed to chemically reactive components such as aliphatic dicarbonyls. The latter compounds, formed during the roasting process, are mutagenic to bacteria but less to mammalian cells. Hydrogen peroxide is not very active but seems to considerably enhance mutagenic properties of methylglyoxal. Phenolic compounds are not mutagenic but rather anticarcinogenic. Benzopyrene and mutagens formed during pyrolysis are not mutagenic whereas roasting of coffee beans at high temperature generates mutagenic heterocyclic amines. In conclusion, the mutagenic potential of coffee and caffeine has been demonstrated in lower organisms, but usually at doses several orders of magnitude greater than the estimated lethal dose for caffeine in humans. Therefore, the chances of coffee and caffeine consumption in moderate to normal amounts to induce mutagenic effects in humans are almost nonexistent.

Teas and tea components as inhibitors of carcinogen formation in model systems and man

BACKGROUND

Epidemiological evidence points to a cancer protective role of green-yellow-orange vegetables and fruits. The involvement of teas as a protective factor in carcinogenesis has not received the attention it seems to merit. To gain relevant information, attempts were made to stimulate in vitro those conditions to which human groups are actually exposed.

METHODS

The inhibitory effects of infusions of Chinese, Japanese, and Ceylonese teas were examined by adding them to a nitrosation mixture consisting of 0.8 mg sodium nitrite and 340 mg equivalent of a widely consumed salt-preserved fish (Pak Wik) and estimating the frequency of mutants in TA 1535 strain of Salmonella typhimurium.

RESULTS

The tea samples exhibited a strong inhibitory effect at concentrations that are actually ingested by man. A comparable inhibition was obtained by several tea phenolics. A second series of experiments dealt with the formation of nitrosoproline (NPRO) which can be strongly inhibited in vitro by the tea infusions and tea phenolics. The effects of the tea infusions and caffeic acid on the endogeneous formation of NPRO in man were examined by having volunteers ingest 300 mg sodium nitrate and 30 min later 300 mg proline, collecting urine samples over a 24-hr period, and estimating the excreted NPRO. The tested teas, at doses regularly consumed, again exerted a strong inhibitory effect on endogeneous NPRO formation in humans. Comparable inhibitory effects were obtained by ingesting caffeic acid, chlorogenic acid, or ferulic acid with the nitrosation mixture.

CONCLUSIONS

These results indicate that the simultaneous intake of teas with food products that are being nitrosated within the stomach of human subjects should exert a protective, beneficial effect.

Coffee consumption and bladder cancer risk

The relation between consumption of regular and decaffeinated coffee and other methylxanthine-containing beverages and bladder cancer was analysed in a case-control study in two different areas of northern Italy (555 cases and 855 controls). The multivariate relative risk (RR) adjusted for smoking, occupation and sociodemographic variables for coffee drinkers versus non-drinkers was 1.3 (95% CI 1.0-1.8). The RR was 1.2 for one cup of coffee per day, 1.4 for two, 1.5 for three and 1.4 for four or more (P = 0.05). RRs for current drinkers were 1.5 (0.9-2.4) for decaffeinated coffee, 0.9 (0.6-1.2) for tea, and 0.6 (0.3-1.4) for cola. With reference to duration of consumption of coffee, RRs were 1.2 for less than 30 years or 1.4 for 30 years or more. Coffee-related RRs were higher in the older age group and in ex-smokers. Among 105 cases and 338 controls who had never smoked, RRs were 1.9 for one or two cups per day, 1.8 for three and 1.5 for four or more (trend not significant). A higher prevalence of coffee drinking among bladder cancer cases than controls was confirmed, with no clear dose-risk relation.

The beneficial and hazardous effects of simple phenolic compounds

The current emphasis on screening the environment for man-made genotoxic and carcinogenic compounds detracts from studies on the possible health hazard or beneficial effects of naturally occurring agents to which humans are exposed daily. The simple phenolics, which are ubiquitous among plants, used as food additives, and ingested daily in milligram quantities, belong to this category of compounds. They induce double-strand DNA breaks. DNA adducts, mutations and chromosome aberrations in a great variety of test systems. However, they can suppress the genotoxic activity of numerous carcinogenic compounds in both in vitro and in vivo assays. This dual function of dietary phenolics also becomes evident when their carcinogenic or anticarcinogenic potential is examined. Some, but not all, phenolics induce precancerous lesions, papillomas and cancers, act as cocarcinogens, and exert a promoting effect in various rodent assays. On the other hand, phenolics have proved to be potent inhibitors of carcinogenesis at the initiation and promotion stages induced by carcinogens and promoters of different molecular structures. The extent to which a health hazard or protective activity of complex dietary mixtures is due to their phenolic content remains an unresolved issue. In addition, these multiple, occasionally contradictory functions of simple phenolics make it difficult to propose their use as chemopreventive agents.

Coffee consumption and bladder cancer risk

The relationship between coffee drinking and the risk of bladder cancer was analyzed within the framework of a French hospital-based case-control study conducted between 1984 and 1987, which included 690 cases of histologically confirmed bladder cancer (599 males and 91 females), and 690 age-, sex- and hospital-matched controls. To dissociate the effects of smoking and coffee drinking among males, the analysis of the male group was restricted to 2 contrasted subgroups: non-smokers on the one hand, and current smokers and inhalers of black tobacco cigarettes on the other. Coffee drinking was found to be significantly associated with the risk of bladder cancer among men in both groups and the increase in the risk was dose-dependent (OR = 1, 2.9, 5.1 respectively, for drinking 1, 2, greater than or equal to 3 cups of coffee per day among non-smokers, and 1, 2.5 and 3.0 respectively, for drinking 1-4, 5-7, greater than cups among smokers). This result was not observed for women.

N-2 acetylation of 2'-deoxyguanosine by coffee mutagens, methylglyoxal and hydrogen peroxide

Coffee shows direct-acting mutagenicity in Salmonella typhimurium TA100 and most of this mutagenicity is due to the synergistic effects of methylglyoxal and hydrogen peroxide. The modifications of deoxyribonucleosides by methylglyoxal plus hydrogen peroxide were studied in vitro. When 2'-deoxyguanosine (6.25 mumole) was treated with methylglyoxal (125 mumole) and hydrogen peroxide (125 mumole) in 5 ml of 0.1 M phosphate buffer (pH 7.4) at 37 degrees C for 3 h, N2-acetyl-2'-deoxyguanosine was formed with a yield of 1.1%. Its formation increased time-dependently. By contrast, no appreciable modification of other deoxynucleosides was detected after their incubation with methylglyoxal and hydrogen peroxide under similar conditions. N2-Acetyl-2'-deoxyguanosine was also formed during incubation of 2'-deoxyguanosine with instant coffee.

A carcinogenicity study of instant coffee in Swiss mice

Commercially available regular instant coffee was given in the diet to barrier-maintained, specified pathogen-free Swiss mice for 2 yr. Groups of 150 males and 150 females were fed diets containing 10, 25 or 50 g instant coffee powder/kg. The animals had already been exposed to coffee in utero. Coffee increased the energy expenditure of the animals as shown by increased daily calorific intake and depressed growth. The overall tumour incidence was inversely correlated to the coffee intake, and no unusual tumour or site of origin was found. The most frequent neoplasms were lymphosarcomas, bronchiolo-alveolar adenomas and adenocarcinomas, as well as hepatocellular adenomas. The incidence of total neoplasms (benign and malignant) decreased from 70.6 and 56.8% in control males and females, respectively, to 34.8 and 36.2%, respectively, in the high-dose group. This decrease, which was essentially due to a reduction in the number of lymphosarcomas and hepatocellular adenomas, was associated with a slower growth rate. The number of leiomyomas in the uterus was slightly increased due to coffee intake as shown by the analysis of positive trend (P less than or equal to 0.05). However, the incidence of this benign tumour was very low; 2.72% of mice affected in the high-dose group, 1.37% in the low-dose group and 0% in the control and medium-dose groups. From this study it is concluded that instant coffee did not increase the incidence of malignant neoplasms in mice when fed at dietary levels of up to 5% for 2 yr.

Analysis of hydrogen peroxide in freshly prepared coffees

Coffee has been shown unequivocally to be genotoxic in vitro, but no genotoxicity has been seen in vivo testing. Since the in vitro genotoxicity appears to be dependent on hydrogen peroxide, it is important to know whether hydrogen peroxide is present in prepared coffee and whether it is being formed during the in vitro testing. We have devised a procedure to measure hydrogen peroxide in prepared coffee using disposable reversed-phase columns to decolourize the coffee and retain its catechols. Hydrogen peroxide was assayed in the eluate from the columns by two chromogenic methods: horseradish-peroxidase-mediated oxidation of phenol red and non-enzymatic oxidation of iodide. Three brands of brewed and instant coffee prepared in the manner recommended to the consumer were studied. Although six of the twelve preparations of coffee contained 3-29 microM-hydrogen peroxide, in the other six none could be detected. Sampling, batch, and aging effects may contribute to the variability in the testing, but there is no indication of greater than 100 microM-hydrogen peroxide levels in freshly prepared coffees, as reported in the literature using other methods. Hydrogen peroxide did form slowly in prepared coffee as the beverage became oxygenated, but it formed quickly if the coffee was diluted by addition to an oxygen-containing solution at neutral pH and then incubated at 37 degrees C. These results strongly suggest that adventitious formation of hydrogen peroxide is a confounding factor in the analytical and in vitro genotoxicological testing of coffees.

Mutagenic activity of various kinds of cheese on the Ames, rec and umu assays

Some kinds of cheese were found to be mutagenic when some inhibiting substances were removed through extraction with MeOH-H2O and then treated with ion exchange resin. After this procedure, 16 types of commercial cheese out of 45 types tested showed significant mutagenicity on Salmonella typhimurium TA104, TA102 and TA97 without S9 mix. Almost all of these cheese also showed genotoxicity on the rec assay and the umu assay. The appearance of mutagenicity in these cheeses seemed to be related to the type of aging during the production process; most of the cheeses with high potency belonged to the blue mold and Propionibacteria-type cheeses and only a few belonged to the white mold, Lactobacillus-type or fresh-type cheeses. The substances inhibiting mutagenicity were isolated and identified as long-chain fatty acids.

Inhibition of in vivo genotoxicity by coffee

The possible role of coffee in modulating the in vivo genotoxicity of the well established genotoxic chemicals, mitomycin C, cyclophosphamide, procarbazine and adriamycin, was evaluated. Coffee was administered orally to mice that received the genotoxic chemicals ip. Genotoxicity was assessed in the bone-marrow micronucleus test. Doses of coffee in the range 225 to 1125 mg (dry weight)/kg body weight caused significant reductions in the in vivo genotoxicity of mitomycin C, cyclophosphamide and procarbazine but not adriamycin. The inhibitory effect was significant when the coffee was given about 2 hr before the genotoxin; there was a lesser effect when coffee was given together with the genotoxin but there was no inhibition when coffee was given 2-4 hr after the genotoxin. An experiment with mitomycin C demonstrated that the reduction in genotoxicity was dependent on the coffee dose. The inhibition of genotoxicity by coffee was observed in bone-marrow cells sampled 24, 48 or 68 hr after injecting cyclophosphamide. Freshly brewed coffee extract, standard instant coffee, decaffeinated instant coffee and freeze-dried home-brew coffee all exerted inhibitory effects.

Chromosome aberrations induced by pyrolysates of carbohydrates in Chinese hamster V79 cells

The clastogenic activity of some pyrolysates of carbohydrates was examined in cultured Chinese hamster V79 cells. These pyrolysates include levoglucosan (LG-I), levoglucosenone (LG-II), furfural (FF), 5-(hydroxymethyl)-2-furfural (HMF), glyoxal (GL), methylglyoxal (MGL), 3-deoxy-D-glucosone (DG) and thiazolidine (TZ). LG-I did not induce a significant number of chromosome aberrations at doses up to 8000 micrograms/ml. In contrast, the related compound LG-II induced aberrations and reduced mitosis in a dose-dependent fashion at around 1/2000 of the LG-I doses. Both furan derivatives, FF and HMF, and both glyoxal derivatives, GL and MGL, induced a significant number of chromosome aberrations and a significant lowering of mitotic activity. Among these compounds, FF and MGL showed stronger clastogenic activity than HMF and GL, respectively. DG slightly but positively induced chromosome aberrations. TZ was one of the most potent clastogens among the compounds examined in this study, showing the highest incidence of aberrant cells with many exchanges at doses inducing a significant lowering of mitotic activity. The results of this study indicate the need for a re-evaluation of the thermal decomposition of carbohydrates as a source of genotoxic contaminants.

Modulation of putative preneoplastic foci in exocrine pancreas of rats and hamsters. Interaction of dietary fat and coffee

The effects of coffee and dietary fat (alone and in combination) on the development of preneoplastic lesions in exocrine pancreas were investigated in rats and hamsters, treated with azaserine or N-nitrosobis(2-oxopropyl)amine, respectively. The animals were given the respective diets (5% or 25% corn oil) and coffee (instead of drinking water) within one week after the treatment with carcinogen. At four months postinitiation, the pancreata were quantitatively examined for the number and size of preneoplastic foci. In rats, coffee alone inhibited growth of acidophilic foci and, moreover, slightly inhibited the positive modulating effect of fat on growth of these foci, pointing to a negative rather than a positive interaction between these two life-style factors. In hamsters, coffee alone enhanced growth of cystic foci, whereas fat alone enhanced growth of ductular foci. An interaction between fat and coffee on pancreatic carcinogenesis in hamsters could not be demonstrated.

Coffee, alcohol, smoking and cancer of the pancreas: a case-control study

A hospital case control study on smoking, alcohol and coffee consumption as risk factors for pancreatic cancer, in which 161 cases were matched to 268 control patients, was conducted in France between 1982 and 1985. The results showed no association between tobacco or alcohol consumption and cancer of the pancreas, whereas coffee consumption was associated with an increased risk [OR of 2 or more cups per day vs. less: 2.27 (1.11-4.64) and 1.45 (0.82-2.55) among females and males respectively]. A dose-response relationship was observed with coffee consumption in both sexes, stronger among females than among males: the linear increase estimates were 2.00 (1.22-3.29) and 1.32 (0.91-1.92) respectively. No interaction was found between coffee and tobacco, whereas the effect of coffee appeared to be limited to non-drinkers of alcohol.

Mutagenicity of food pellets from human diets in The Netherlands

Food pellets from human diets, prepared according to mean consumption figures in The Netherlands, were assessed on mutagenicity and mutagens were identified. Three types of human meals were compared: raw (C), heated (D) and heated with vegetables and fruit (E, a complete meal). In addition 2 animal diets were tested: commercial control diet (A), and a control diet to which vegetables and fruit had been added (B). All human diets contained: 40.6 energy (E)% fat, 13.2 E% protein, 46.2 E% carbohydrate and 5.2% (w/w) fibre. For animal diets these figures were 21.6, 26.0, 52.4 and 10.7% respectively. After extraction samples were tested in the Salmonella-microsome test, tester strains TA1538, TA98 and TA100. Human diets with heated products (D, E) were both clearly mutagenic with approximately 300-500 revertants per gram. Food pellets from animal diets (A, B) displayed no mutagenic activity. HPLC-derived chromatographic fractions of diets D and E showed 3 large mutagenic areas identified as IQ (2-amino-3 methyl-imidazo-[4,5-f]quinoline) and MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, DiMeIQx (2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline and PhIP (2-amino-6-phenylimidazo[4,5-b]pyridine) and other mutagens not completely defined. This mutagen profile was similar to that found previously for fried beef. Mass estimates for these potent mutagens amounted to 15-20 micrograms/kg. Health implications of these findings are discussed. As IQ, MeIOx and DiMeIQx have been found to be weakly carcinogenic in rodents and many other initiating and modulating factors may be present in a complex human diet, a chronic toxicity study is indicated.

Study of the causes of direct-acting mutagenicity in coffee and tea using the Ara test in Salmonella typhimurium

The mutagenic activities of 6 of the chemicals identified in coffee solutions were assayed with the Salmonella Ara test, under experimental conditions optimized for coffee mutagenicity. Caffeine was the only non-mutagenic compound. Among the other 5 chemicals, hydrogen peroxide was the strongest mutagen and chlorogenic acid the weakest; methylglyoxal, glyoxal and caffeic acid exhibited intermediate mutagenicities. The minimal mutagenic doses of these components correlated negatively with their relative concentrations in coffee. It was concluded that chlorogenic acid, caffeic acid, glyoxal and methylglyoxal cannot contribute alone to the mutagenicity of coffee in the Ara test, since their minimal mutagenic concentrations were much higher than their respective levels in the coffee samples assayed. By contrast, 40-60% of the mutagenic activity in coffee and also in tea could be attributed to their H2O2 contents. Catalase abolished more than 95% of the mutagenic activity of coffee, as detected by the Ara test. A similar sensitivity to catalase has been reported by other authors in relation to the coffee mutagenicity identified by the Salmonella His test. Nevertheless, the results presented in this paper suggest that the Ara forward and the His reverse mutation tests are sensitive to the mutagenicity of different constituents in coffee solutions. We propose that the His test, sensitive at high coffee doses, mainly recognizes the mutagenicity of methylglyoxal, whilst the Ara test, sensitive at low coffee doses, mainly detects the mutagenic activity of hydrogen peroxide. The data reported also suggest that the direct-acting mutagenicity(ies) detected by the Ara test in tea solutions is (are) based on similar, if not identical, mechanisms.