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PubMed1992

The effect of filtered-coffee consumption on plasma lipid levels. Results of a randomized clinical trial.

OBJECTIVE: --To determine the effect of filtered-coffee consumption on plasma lipoprotein cholesterol levels in healthy men. DESIGN: --Randomized controlled trial with an 8-week washout period followed by an 8-week intervention period during which men were randomly assigned to drink 720 mL/d of caffeinated coffee, 360 mL/d of caffeinated coffee, 720 mL/d of decaffeinated coffee, or no coffee. SETTING: --Outpatient clinical research center in a university medical center. PARTICIPANTS: --One hundred healthy male volunteers. OUTCOME MEASURE: --Changes in plasma lipoprotein cholesterol levels during the intervention period. RESULTS: --Men who consumed 720 mL of caffeinated coffee daily had mean increases in plasma levels of total cholesterol (0.24 mmol/L, P = .001), low-density lipoprotein cholesterol (0.17 mmol/L, P = .04), and high-density lipoprotein cholesterol (0.08 mmol/L, P = .03). No significant changes in these plasma lipoprotein levels occurred in the other groups. Compared with the group who drank no coffee the group who drank 720 mL/d of caffeinated coffee had increases in plasma levels of total cholesterol (0.25 mmol/L, P = .02), low-density lipoprotein cholesterol (0.15 mmol/L, P = .17), and high-density lipoprotein cholesterol (0.09 mmol/L, P = .12) after adjustment for changes in diet. CONCLUSION: --Consumption of 720 mL/d of filtered, caffeinated coffee leads to a statistically significant increase in the plasma level of total cholesterol, which appears to be due to increases of both low-density lipoprotein and high-density lipoprotein cholesterol levels.

Adult↗

PubMed1987

Effects of naloxone and coffee on anterior pituitary hormones.

Both naloxone, a specific opiate antagonist, and caffeine and other components of coffee powders show influences on opiate receptors and on the secretion of some pituitary hormones. In order to study the possible effect of naloxone and coffee on the secretion pattern of hypophyseal hormones in man, experiments were performed in normal volunteers using either naloxone or coffee alone or both substances. Five healthy normal males, aged 25-30 years, received on three separate occasions and in random order: (i) coffee (4 cups of Italian style "espresso" coffee); or (ii) naloxone 12 micrograms/kg i.v.; or (iii) coffee plus naloxone simultaneously. The results show that naloxone given alone did not modify basal plasma PRL, GH, TSH, FSH or cortisol levels but significantly increased basal LH concentrations. On the other hand, the absorption of four cups of coffee did not modify the values of any of the hormones studied. The combination of the two drugs (coffee + naloxone) did not alter the response of the hormones studied to naloxone alone. It was concluded that coffee drinking, at least in these experimental conditions, does not appear to have any influence on anterior pituitary hormone secretion. Naloxone, on the other hand, is able to stimulate LH secretion even at very low doses.

Adult↗

PubMed2003

Status of free radicals in Indian monsooned coffee beans gamma-irradiated for disinfestation.

Free radicals in two cultivars of Indian monsooned coffee beans, gamma-irradiated for hygienic and quarantine purposes, were examined by entrapping the small amount of samples in potassium chloride powder in ESR quartz tubes. In contrast to a prominent free radical signal at g = 2.002, observed in spermoderm (silver skin) and cotyledon (whole seed without skin) parts of normal coffee beans, the same was not discernible in monsooned coffee bean parts of both cultivars. The ESR signal was found to be more prominent in the spermoderm than in the whole seed portion of the normal coffee beans. Common practices of roasting and powdering were found to generate quantitatively more free radicals in coffee beans than gamma-irradiation alone. Phenols, contributing maximally to observed free radical signals in coffee beans, were significantly different in normal and monsooned coffee beans. These observations on insignificant free radical population in irradiated monsooned coffee beans may be attributed to their inherent possession of high water activity, favoring decay of free radicals produced. Textural studies with monsooned coffee beans, before and after mild heat treatments, supported these findings.

Chlorogenic Acid↗

PubMed2005

Screening of raw coffee for thiol binding site precursors using "in bean" model roasting experiments.

The purpose of the following study was to investigate the influence of coffee roasting on the thiol-binding activity of coffee beverages, and to investigate the potential of various green bean compounds as precursors of thiol-binding sites by using promising "in bean" model roast experiments. Headspace gas chromatographic analysis on coffee brews incubated in the presence of the roasty-sulfury smelling 2-furfurylthiol for 20 min at 30 degrees C in septum-closed vessels revealed that the amounts of "free" thiol decreased drastically with increasing the roasting degree of the beans used for preparation of the brews. A half-maximal binding capacity (BC(50)) of 183 mg of 2-furfurylthiol per liter of standard coffee beverage was determined for a roasted coffee (CTN value of 67), thus demonstrating that enormous amounts of the odor-active thiol are "bound" by the coffee. Furthermore, biomimetic "in bean" precursor experiments have been performed in order to elucidate the precursor for the thiol-binding sites in the raw coffee bean. These experiments opened the possibility of studying coffee model reactions under quasi-natural roasting conditions and undoubtedly identified chlorogenic acids as well as thermal degradation products caffeic acid and quinic acid as important precursors for low-molecular-weight thiol-binding sites. In particular, when roasted in the presence of transition metal ions, chlorogenic acids and even more caffeic acid showed thiol-binding activity which was comparable to the activity measured for the authentic coffee brew.

Binding Sites↗

PubMed2004

Coffee bean extracts rich and poor in kahweol both give rise to elevation of liver enzymes in healthy volunteers.

BACKGROUND: Coffee oil potently raises serum cholesterol levels in humans. The diterpenes cafestol and kahweol are responsible for this elevation. Coffee oil also causes elevation of liver enzyme levels in serum. It has been suggested that cafestol is mainly responsible for the effect on serum cholesterol levels and that kahweol is mainly responsible for the effect on liver enzyme levels. The objective of this study was to investigate whether coffee oil that only contains a minute amount of kahweol indeed does not cause elevation of liver enzyme levels. METHODS: The response of serum alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) to Robusta coffee oil (62 mg/day cafestol, 1.6 mg/day kahweol) was measured in 18 healthy volunteers. RESULTS: After nine days one subject was taken off Robusta oil treatment due to an ALAT level of 3.6 times the upper limit of normal (ULN). Another two subjects stopped treatment due to other reasons. After 16 days another two subjects were taken off Robusta oil treatment. One of those subjects had levels of 5.8 ULN for ALAT and 2.0 ULN for ASAT; the other subject had an ALAT level of 12.4 ULN and an ASAT level of 4.7 ULN. It was then decided to terminate the study. The median response of subjects to Robusta oil after 16 days was 0.27 ULN (n = 15, 25th,75th percentile: 0.09;0.53) for ALAT and 0.06 ULN (25th,75th percentile -0.06;0.22) for ASAT. CONCLUSIONS: We conclude that the effect on liver enzyme levels of coffee oil containing hardly any kahweol is similar to that of coffee oil containing high amounts of kahweol. Therefore it is unlikely that kahweol is the component of coffee oil that is responsible for the effect. Furthermore, we conclude that otherwise unexplained elevation of liver enzyme levels observed in patients might be caused by a switch from consumption of filtered coffee to unfiltered coffee.

Journal Article↗

PubMed2006

Coffee consumption and risk of type 2 diabetes mellitus: an 11-year prospective study of 28 812 postmenopausal women.

BACKGROUND: Coffee intake may be associated with reduced risk of type 2 diabetes mellitus because of minerals, phytochemicals, and antioxidants in coffee, but the role of caffeine is unclear. Our objective was to examine the association between total, caffeinated, and decaffeinated coffee intake, as assessed by food frequency questionnaire at baseline, and risk of incident type 2 diabetes mellitus. METHODS: This prospective analysis of the Iowa Women's Health Study (1986-1997) included 28 812 postmenopausal women free of diabetes and cardiovascular disease in the general community. The main outcome measure was incident type 2 diabetes mellitus as determined by mailed questionnaire. RESULTS: Coffee intake was categorized as 0, less than 1, 1 to 3, 4 to 5, and 6 or more cups per day. During 11 years of follow-up, there were 1418 incident cases of diabetes. Relative risks (RRs) were adjusted for a variety of demographic, adiposity, and lifestyle measures. Compared with women who reported 0 cups of coffee per day, women who consumed 6 or more cups per day had a 22% lower risk (RR = 0.78; 95% confidence interval [CI], 0.61-1.01) of diabetes (P for linear trend across categories, .06). This association appeared to be largely explained by decaffeinated coffee (RR = 0.67; 95% CI, 0.42-1.08; P for trend, .006) rather than regular coffee (RR = 0.79; 95% CI, 0.59-1.05; P for trend, .90). Intake of magnesium and phytate did not explain these associations. Intakes of caffeine from all sources was not associated with risk of diabetes. CONCLUSION: Coffee intake, especially decaffeinated, was inversely associated with risk of type 2 diabetes mellitus in this cohort of postmenopausal women.

Aged↗

PubMed1991

Caffeine self-administration, withdrawal, and adverse effects among coffee drinkers.

Twenty-two coffee drinkers (three to seven cups per day) underwent repeated double-blind trials to test for caffeine self-administration, withdrawal, and adverse effects. Each trial consisted first of a randomized crossover period of 1 day of decaffeinated coffee and 1 day of caffeinated coffee (100 mg) to assess withdrawal and adverse effects of caffeine. Next, subjects were given 2 days of concurrent access to the two coffees. The relative use of the two coffees was used to assess caffeine self-administration. Reliable caffeine self-administration occurred in three of 10 subjects in study 1 and seven of 12 subjects in study 2. Withdrawal symptoms were headaches, drowsiness, and fatigue. The major adverse effect from self-administration was tremulousness. The occurrence of headaches on substitution of decaffeinated coffee prospectively predicted subsequent self-administration of caffeine. These results indicate that some coffee drinkers exhibit signs of a caffeine dependence, ie, they self-administer coffee for the effects of caffeine, have withdrawal symptoms on cessation, and experience adverse effects.

Adult↗

PubMed1999

A prospective study of coffee consumption and the risk of symptomatic gallstone disease in men.

CONTEXT: Coffee has several metabolic effects that could reduce the risk of gallstone formation. OBJECTIVE: To examine the association between coffee consumption and the risk of symptomatic gallstone disease in men. DESIGN AND SETTING: The Health Professionals Follow-up Study, a prospective cohort study, in which the consumption of coffee and other caffeinated drinks was assessed starting in 1986 as part of the 131-item food frequency questionnaire given to US male health professionals with follow-up through 1996. PARTICIPANTS: A total of 46008 men, aged 40 to 75 years in 1986, without history of gallstone disease. MAIN OUTCOME MEASURES: Newly symptomatic gallstone disease (diagnosed by ultrasonography or x-ray) or a cholecystectomy. RESULTS: During 404 166 person-years of follow-up, 1081 subjects reported symptomatic gallstone disease, of whom 885 required cholecystectomy. After adjusting for other known or suspected risk factors, compared with men who did not consume regular coffee in 1986 and 1990, the adjusted relative risk (RR) for those who consistently drank 2 to 3 cups of regular coffee per day was 0.60 (95% confidence interval [CI], 0.42-0.86) and for those who drank 4 or more cups per day the RR was 0.55 (95% CI, 0.33-0.92). All coffee brewing methods showed a decreased risk. The risk of symptomatic gallstone disease also declined with increasing caffeine intake (P for trend = .005). After controlling for known or suspected risk factors, the RR for men in the highest category of caffeine intake (>800 mg/d) compared with men in the lowest category (< or =25 mg/d) was 0.55 (95% CI, 0.35-0.87). In contrast, decaffeinated coffee was not associated with a decreased risk. CONCLUSIONS: In this cohort of US men, coffee consumption may have helped to prevent symptomatic gallstone disease.

Adult↗

PubMed1997

Coffee and tea intake and risk of cancers of the colon and rectum: a study of 3,530 cases and 7,057 controls.

The relationship between coffee, decaffeinated coffee and tea intake and risk of cancers of the colon and rectum was considered combining data from 2 case-control studies, one conducted between 1985 and 1991 in Northern Italy and the other between 1991 and 1996 in 6 Italian centers. Cases were patients below age 80, with histologically confirmed cancer of the colon (n = 2,166) or rectum (n = 1,364), and controls were 7,057 patients admitted to hospital for a wide spectrum of acute, non-neoplastic, non-digestive tract diseases. Compared with coffee non-drinkers, the risk of colon cancer was reduced in drinkers of 4 or more cups/day [multivariate odds ratios (ORs) 0.73; 95% confidence intervals 0.60-0.89), with a significant trend in risk with dose; no significant association emerged between coffee drinking and risk of rectal cancer (OR 1.00 for drinkers of 4 or more cups/day). Decaffeinated coffee was consumed in small amounts by about 4% of cases and controls and the OR was 0.92 for colon and 0.88 for rectal cancers. Tea consumption was generally limited to 1 cup/day or to occasional intake and did not substantially modify the risk of colon and rectal cancers. No significant heterogeneity was found for the inverse relationship between coffee intake and colon cancer risk across strata of age at diagnosis, sex, smoking status, total alcohol and meat and vegetable intake, while the protection of coffee was stronger in people eating 3 or more meals/day. Thus, our results confirm that coffee intake has a quantifiable protective effect on colon cancer risk.

Adult↗

PubMed1976

Dose-related sleep disturbances induced by coffee and caffeine.

In a 13-night sleep laboratory study, each of 18 normal young adult males twice received 1 cup of warm water, 1-, 2-, and 4-cup equivalents of regular coffee, a 4-cup equivalent of decaffeinated coffee, and a 4-cup equivalent of caffeine. All beverages were administered 30 min before bedtime according to a balanced Latin-square design. Regular coffee produced dose-related changes in most standard electroencephalogram-electrooculogram (EEG-EOG) sleep parameters, and the 4-cup equivalents of regular coffee and caffeine produced equivalent effects. Decaffeinated coffee had no effect. Regular coffee and caffeine caused rapid eye movement (REM) sleep to shift to the early part of the night and stages 3 and 4 sleep to shift to the later part. Coffee also produced dose-related changes in several subjects estimates of sleep characteristics. These results suggest that coffee and caffeine may be used in normal subjects to induce symptoms mimicking those of insomnia. Such a tool should promote further understanding of insomnia.

Adult↗

PubMed2002

Efficacy and residues of phloxine B and uranine for the suppression of Mediterranean fruit fly in coffee fields.

The field efficacy of a bait containing phloxine B, uranine and Provesta 621 protein was tested against Mediterranean fruit fly (Ceratitis capitata; Medfly) by aerial and ground spraying in about 84 ha of coffee fields in Kauai, Hawaii, USA. Concurrently, soil and crop samples were collected from the aerially sprayed field and its unsprayed control field for residue studies. Efficacy of the sprays was assessed through trapping with both protein-baited and trimedlure-baited traps and through the infestation level of coffee cherries collected at least three-quarters ripe. The C capitata population was low at the start of the aerial and ground spray studies, but dramatically increased in the control fields. This increase coincided with initial ripening of coffee cherries. During times of peak population levels, C capitata populations were reduced by more than 91% in the ground-sprayed field and 99% in the aerial-sprayed field, relative to the populations in their respective control fields and based on protein-baited trap catches. Results of residue analyses indicated that uranine dissipated quickly compared with phloxine B on coffee and soil. Coffee samples collected at pre-spray periods had phloxine B residues of 7.2-25.5 ng g-1 on berries. Phloxine B concentrations were much higher on coffee leaves (163-1120 ng g-1). Lower concentrations of the dye were found from coffee samples collected during rainy days. Average phloxine B concentrations immediately after spraying were 56 and 2840 ng g-1 in coffee berries and leaves, respectively. Dissipation of phloxine B on berries was fast, with a half-life (t1/2) of 3 days. Dissipation of phloxine B on leaves was fitted to two linear phases: the initial (0-4 days) with a shorter t1/2 of 3 days and the later phase (4-28 days) with a longer t1/2 of 15 days. Average concentrations of phloxine B in the top soil ranged from 50 to 590 ng g-1 at pre-spray. Phloxine B initial concentration (770 ng g-1) reached a plateau immediately after the last spraying, but showed a steady decline over time with t1/2 of 16 days. Fast dissipation of the dyes in the field indicates that these chemicals may be environmentally compatible and therefore a promising alternative for fruit fly control.

Animals↗

PubMed1994

Coffee, tea, and lifestyle.

BACKGROUND: Previous reports have indicated that coffee drinking is associated with an unhealthy lifestyle, compared with tea drinking, which may confound the effect in relation to coronary risk factors. METHODS: In a population sample of 2,400 25- to 64-year-old men and women, associations of lifestyle factors with coffee and tea consumption were analyzed. Lifestyle factors were related to four realms of behavior: smoking, eating, drinking, and physical activity. RESULTS: Overall response rate exceeded 77%. Twenty-two behavioral factors were included in the analysis and controlled for age and sex. Mean daily cigarette consumption, the consumption of main fat sources (meat and sausages) and lemonade drinking increased with coffee and decreased with tea consumption. Conversely, intake of fresh fruits, drinking of juice or mineral water, and physical activity on the way to work decreased with coffee and increased with tea. The strongest associations were between coffee, than tea, and cigarette smoking. Controlling smoking (and physical activity) changed trends mainly with respect to alcoholic drinks. CONCLUSIONS: We conclude that drinking coffee is positively associated with factors that promote coronary heart disease, while drinking tea is associated with a preventive lifestyle. Factors supporting these results were found located in all realms of lifestyle for both for coffee and tea. Therefore, investigations on the health effects of coffee and tea must be carefully controlled for confounding behavioral parameters.

Adult↗

PubMed1985

[Acids in coffee. XI. The proportion of individual acids in the total titratable acid].

22 acids in ground roast coffees and instant coffees were determined by GLC of their silyl derivatives (after preseparation by gel electrophoresis) or isotachophoresis. The contribution to the total acidity (which was estimated by titration to pH 8 after cation exchange of the coffee solutions) was calculated for each individual acid. The mentioned acids contribute with 67% (roast coffee) and 72% (instant coffee) to the total acidity. In the first place citric acid (12.2% in roast coffee/10.7% in instant coffee), acetic acid (11.2%/8.8%) and the high molecular weight acids (8%/9%) contribute to the total acidity. Also to be mentioned are the shares of chlorogenic acids (9%/4.8%), formic acid (5.3%/4.6%), quinic acid (4.7%/5.9%), malic acid (3.9%/3%) and phosphoric acid (2.5%/5.2%). A notable difference in the contribution to total acidity between roast and instant coffee was found for phosphoric acid and pyrrolidonecarboxylic acid (0.7%/1.9%). It can be concluded that those two acids are formed or released from e.g. their esters in higher amounts than other acids during the production of instant coffee.

Acids↗

PubMed1977

[Coffee and health].

Coffee as a rule develops stimulating effects on the central nervous system, heart and circulation which are mainly caused by caffeine. In certain cases coffee may also have a sedative effect and sometimes even it is useful to fall asleep quickly. Furthermore coffee may be advantageous in the treatment of some functional disorders caused by lacking of dopamine, because coffee is able to increase the dopamine formation in brain. Concerning the effects of coffee in the gastrointestinal-tract and liver-bile system caffeine is only of secondary importance. Hereby certain roasting substances, possibly also chlorogenic acid or caffeic acid should be responsible for the stimulating effects observed in these organs. These stimulating effects could be caused whether directly or indirect e.g. by liberating gastrin or other gastrointestinal hormones. Vitamin niacin, which is formed in greater amounts from trigonelline during the roasting process, may also be important from the nutritional standpoint. Therefore coffee may be prescribed as a true drug in cases of deficiency in vitamin niacin or also in the pellagra disease. By extensive epidemiological studies performed lately it could be demonstrated that there exists no correlation between coffee consumption and certain risk factors as hypertension, heart infarction, diabetes, gout or cancer diseases. Furthermore there was no evidence that coffee or its caffeine content are able to induce genetic alterations or even malformations.

Animals↗

PubMed2006

Ant patchiness: a spatially quantitative test in coffee agroecosystems.

Arboreal ants form patchy spatial patterns in tropical agroforest canopies. Such patchy distributions more likely occur in disturbed habitats associated with lower ant diversity and resource availability than in forests. Yet, few studies have quantitatively examined these patchy patterns to statistically test if ants are non-randomly distributed or at what scale. Coffee agroecosystems form a gradient of management intensification along which vegetative complexity and ant diversity decline. Using field studies and a spatially explicit randomization model, I investigated ant patchiness in coffee agroecosystems in Chiapas, Mexico varying in management intensity to examine if: (1) coffee intensification affects occurrence of numerically dominant ants, (2) numerical dominants form statistically distinguishable single-species patches in coffee plants, (3) shade trees play a role in patch location, and (4) patch formation or size varies with management intensity. Coffee intensification correlated with lower occurrence frequency of numerically dominant species generally and of one of four taxa examined. All dominant ant species formed patches but only Azteca instabilis was patchy around shade trees. Ant patchiness did vary somewhat with spatial scale and with strata (within the coffee layer vs around shade trees). Patchiness, however, did not vary with management intensity. These results provide quantitative evidence that numerically dominant ants are patchy within the coffee layer at different scales and that shade tree location, but not coffee management intensity, may play a role in the formation of patchy distributions.

Animals↗

PubMed2000

A naturalistic investigation of the effects of day-long consumption of tea, coffee and water on alertness, sleep onset and sleep quality.

RATIONALE: The effects of caffeine, especially caffeinated coffee, on human performance have been extensively studied. However, few studies have been naturalistic representations of how tea/coffee is normally consumed in terms of dose and time of consumption. OBJECTIVES: This study investigated the effects of day-long consumption of tea, coffee and water on cognitive and psychomotor performance, and sleep quality at night. METHODS: Thirty healthy volunteers received equal volume drinks equivalent to either 1 or 2 cups of tea (containing 37.5 mg or 75 mg caffeine), or coffee (75 mg or 150 mg caffeine), or water, in a randomised five-way crossover design. Drinks were administered on four occasions during the day (0900, 1300, 1700 and 2300 hours). A psychometric battery consisting of critical flicker fusion (CFF), choice reaction time (CRT) and subjective sedation (LARS) tests, was administered pre-dose and at frequent time points post-dose. The Leeds Sleep Evaluation Questionnaire (LSEQ) was completed each morning and a wrist actigraph was worn for the duration of the study. RESULTS: Caffeinated beverages maintained CFF threshold over the whole day (P<0.05), independent of caffeine dose or beverage type. During the acute phase of beverage ingestion, caffeine significantly sustained performance compared to water after the first beverage for CFF and subjective sedation (P<0.05), and after the second beverage for the Recognition component of the CRT task (P<0.05). Additionally, there were significant differences between tea and coffee at 75 mg caffeine after the first drink. Compared to coffee, tea produced a significant increase in CFF threshold between 30 and 90 min post-consumption (P<0.01). However, following the second beverage caffeinated coffee at 75 mg significantly improved reaction time (P<0.05), compared to tea at the same dose, for the Recognition component of the CRT task. Caffeinated beverages had a dose dependent negative effect on sleep onset (P<0.001), sleep time (P<0.001) and sleep quality (P<0.001). CONCLUSIONS: These results indicate that ingestion of caffeinated beverages may maintain aspects of cognitive and psychomotor performance throughout the day and evening when caffeinated beverages are administered repeatedly. This study also demonstrates that day-long tea consumption produces similar alerting effects to coffee, despite lower caffeine levels, but is less likely to disrupt sleep. Other differences between tea and coffee were more subtle, and require further investigation.

Adult↗

PubMed1989

Effects of regular and decaffeinated coffee on fetal breathing and heart rate.

The effects of maternal consumption of regular or decaffeinated coffee on the fetus were determined in eight pregnant women at 32 to 36 weeks of gestation. This was a single-blind crossover study in which two cups of caffeinated or decaffeinated coffee were consumed after an overnight fast. The total maternal caffeine ingested was 454 +/- 4 mg for regular coffee and 12 +/- 0.4 mg for decaffeinated coffee. Maternal consumption of regular coffee was associated with a twofold increase in the incidence of fetal breathing activity and a significant fall in baseline fetal heart rate. Decaffeinated coffee also increased the incidence of fetal breathing activity and produced a slight reduction in fetal heart rate. These results indicate that maternal consumption of regular and decaffeinated coffee can stimulate fetal breathing. Moreover, these results suggest that caffeinated coffee can produce baseline shifts in fetal heart rate.

Blood Glucose↗

PubMed1994

The inhibitory effects of coffee on radical-mediated oxidation and mutagenicity.

Hydrogen peroxide (H2O2) has been implicated as a major contributor to coffee mutagenicity and genotoxicity in vitro. We have used three assays to show the gradual formation of H2O2 in freshly prepared roasted ground coffee and in instant coffees over time reaching levels of 400-450 microM after a 1-h incubation period. Formation of H2O2 occurs through an auto-oxidation process where polyphenolics, in the presence of transition metals, reduce atmospheric oxygen. However, because of these polyphenolics, coffee also possesses in vitro antioxidant activity as shown by its capacity to inhibit lipid peroxidation in Fenton-catalysed hydroxylation reactions. The pro- and antioxidative effects of coffee are also reflected in its mutagenic and antimutagenic activity in the Ames test. Coffee is directly mutagenic in strains TA100 and TA102 due to H2O2 formation. However, coffee is also an antioxidant and antimutagen. This beverage exerts a strong protective effect against the mutagenicity and cytotoxicity induced by the oxidant t-butylhydroperoxide (t-BOOH). Thus, coffee, like many antioxidants, exhibits dual effects in vitro which are highly dependent upon parameters such as dose, atmospheric oxygen, transition metals as well as the biological and chemical endpoints used for measurement. Consequently, the data obtained on the pro- and antioxidant properties of foods and beverages from in vitro bioassays must be interpreted with caution and the results are not easily extrapolated in vivo to assess the impact on human health.

8-Hydroxy-2'-Deoxyguanosine↗