Caffeine content of specialty coffees

Caffeine is the world's most widely consumed drug with its main source found in coffee. We evaluated the caffeine content of caffeinated and decaffeinated specialty coffee samples obtained from coffee shops. Caffeine was isolated from the coffee by liquid-liquid extraction and analyzed by gas chromatography with nitrogen-phosphorus detection. In this study, the coffees sold as decaffeinated were found to have caffeine concentrations less than 17.7 mg/dose. There was a wide range in caffeine content present in caffeinated coffees ranging from 58 to 259 mg/dose. The mean (SD) caffeine content of the brewed specialty coffees was 188 (36) mg for a 16-oz cup. Another notable find is the wide range of caffeine concentrations (259-564 mg/dose) in the same coffee beverage obtained from the same outlet on six consecutive days.     

An examination of consumer exposure to caffeine from retail coffee outlets

Objective

To analyse the distribution of caffeine doses obtainable from espresso coffee sold by a sample of commercial coffee vendors located on the Gold Coast, Qld, Australia.

Design

A cross section of “Espresso/short black” coffee samples were purchased and analysed for their caffeine content using micellar electrokinetic capillary chromatography (MEKC). Coffees were collected using systematic cluster sampling across five major retail centres.

Results

Ninety-seven espresso samples were analysed. The mean (±SD) quantity of caffeine was 106 ± 38 mg/serve with a concentration of 2473 ± 1092 mg/l. There was considerable variation in caffeine content. The range per serve was 25–214 mg whilst the concentration range was 580–7000 mg/l. Twenty-four samples (24.7%) contained 120 mg of caffeine or higher and 12 samples (12.3%) exceeded 167 mg per serve.

Conclusions and implications

The number of heavily caffeinated samples differentiates these findings from frequently cited caffeine values and supports similar data recently collected throughout the United Kingdom. As a result, the accuracy of any previous intake modelling regarding caffeine use in the Australian population is in doubt. The present data suggests that the probability of consumer exposure to high caffeine doses is greater than previously anticipated. Greater sample numbers from a broader selection of venues is required to confirm the extent of caffeine content variance within retail ground coffees.     

Effect of dose on the ability of caffeine to serve as a reinforcer in humans

This study tested the effects of dose on the reinforcing effects of caffeine in humans. Eight moderate coffee drinkers were given concurrent access to decaffeinated coffee vs. decaffeinated coffee to which different doses of caffeine (25, 50, 150 and 200mg/cup) were added. Subjects were tested across several independent double-blind trials. The coffees with 25mg of caffeine were repeatedly self-administered at a rate greater than that of decaffeinated coffee in two of six subjects, the 50mg dose in four of eight subjects, the 150mg dose in three of six subjects, and the 200mg dose in none of the three subjects tested. Headaches, drowsiness and fatigue occurred with use of decaffeinated coffee in five subjects. When these symptoms occurred, there was a greater probability of self-administration of the caffeinated coffee. We conclude that doses of caffeine similar to those in tea or soda can serve as reinforcers.     

Forced-choice versus free-choice procedures: Caffeine self-administration in humans

Methodological comparisons of procedures for drug self-administration are rare. In studies examining the reinforcing effect of caffeine in humans, caffeine self-administration usually has been inferred from performance under forced-choice procedures. In the present experiment, caffeine self-administration via coffee was compared under forced-choice and free-choice conditions; i.e., when subjects were and were not required to use a minimum number of coffees. Ten moderate coffee drinkers (2–7 cups/day) were assigned to forced- and free-choice conditions using a randomized cross-over design. Under each choice condition, subjects completed six independent, double-blind trials, consisting of a 2-day exposure period followed by a 2-day test period. During exposure, subjects consumed either decaffeinated or caffeinated (100 mg/serving) coffee on day 1 and the other coffee on day 2. During the test period, subjects had concurrent access to the same decaffeinated and caffeinated coffees. Under the forced-choice condition, subjects were required to drink at least four cups of coffee per day during the test period. Under the free-choice condition, subjects did not have a minimum-cup requirement. In general, the relative rate at which subjects self-administered caffeinated versus decaffeinated coffee was similar across choice conditions, even though subjects self-administered significantly fewer cups of both coffee types under the free-choice than the forced-choice condition. These results suggest that, at least for caffeine, forced-choice and free-choice procedures produce comparable results. Whether this finding generalizes to a context in which caffeine or another drug is more robustly self-administered, remains to be determined.Supported by grant DA-04843, T32-DA07242, and Research Scientist Development Award DA-00109 (J.R.H) from the National Institute on Drug Abuse.     

Coffee and Caffeine Protect against Liver Injury Induced by Thioacetamide in Male Wistar Rats

Coffee intake has been inversely related to the incidence of liver diseases, although there are controversies on whether these beneficial effects on human health are because of caffeine or other specific components in this popular beverage. Thus, this study evaluated the protective effects of coffee or caffeine intake on liver injury induced by repeated thioacetamide (TAA) administration in male Wistar rats. Rats were randomized into five groups: one untreated group (G1) and four groups (G2–G5) treated with the hepatotoxicant TAA (200 mg/kg b.w., i.p.) twice a week for 8 weeks. Concomitantly, rats received tap water (G1 and G2), conventional coffee (G3), decaffeinated coffee (G4) or 0.1% caffeine (G5). After 8 weeks of treatment, rats were killed and blood and liver samples were collected. Conventional and decaffeinated coffee and caffeine intake significantly reduced serum levels of alanine aminotransferase (ALT) (p < 0.001) and oxidized glutathione (p < 0.05), fibrosis/inflammation scores (p < 0.001), collagen volume fraction (p < 0.01) and transforming growth factor β‐1 (TGF‐β1) protein expression (p ≤ 0.001) in the liver from TAA‐treated groups. In addition, conventional coffee and caffeine intake significantly reduced proliferating cellular nuclear antigen (PCNA) S‐phase indexes (p < 0.001), but only conventional coffee reduced cleaved caspase‐3 indexes (p < 0.001), active metalloproteinase 2 (p ≤ 0.004) and the number of glutathione S‐transferase placental form (GST‐P)‐positive preneoplastic lesions (p < 0.05) in the liver from TAA‐treated groups. In conclusion, conventional coffee and 0.1% caffeine intake presented better beneficial effects than decaffeinated coffee against liver injury induced by TAA in male Wistar rats.     

Influence of genetic polymorphisms and habitual caffeine intake on the changes in blood pressure,pulse rate,and calculation speed after caffeine intake: A prospective,double blind,randomized trial in healthy volunteers

The aim of this study was to investigate the contribution of gene polymorphisms, in combination with habitual caffeine consumption, to the effect of caffeine intake on hemodynamic and psychoactive parameters. A double-blind, prospective study was conducted with 201 healthy volunteers randomly allocated 2:1 to the caffeinated group (150 mL decaffeinated coffee with additional 200 mg caffeine) or decaffeinated group (150 mL decaffeinated coffee). We measured the changes in blood pressure (BP) and calculation speed upon coffee intake, stratifying with gene polymorphisms, e.g., those in adenosine A_2A receptor (ADORA2A) and cytochrome P450 (CYP) 1A2, and daily caffeine consumption (≤90 mg/day and >90 mg/day). Overall, caffeine intake independently increased BP and calculation speed (p-values < 0.05), irrespective of the polymorphisms. In stratified analysis, a statistical significance within the caffeinated group was observed for the change in systolic BP in the stratum of CYP1A2 polymorphism with daily caffeine consumption ≤90 mg/day: change in systolic BP in the CYP1A2 rs762551 CC group (mean ± SD = 11.8 ± 5.9) was higher than that in the AA/CA group (4.1 ± 5.5). Gene polymorphisms may limitedly modify the effect of caffeine intake on hemodynamic parameters in combination with habitual caffeine consumption.     

Caffeine as an intensifier of stress-induced hormonal and pathophysiologic changes in mice

Psychosocially stressed male mice competing in a Henry-Stephens complex population cage develop hypertension, cardiovascular damage, and chronic interstitial nephritis. Their plasma renin, noradrenaline, corticosterone, and adrenal-catecholamine synthetic enzymes are increased and they die prematurely. Adding 3.3 mg of caffeine a day per kilogram of mouse body weight (the equivalent of 20 μg/ml decaffeinated coffee) to their drinking water significantly intensifies most of these changes. A dose of 90 mg/kg of caffeine (the equivalent of 560 μg/ml, i.e., brewed tea or coffee) further increases the effects. The drug-induced enhancement of competitive social stimulation of the neuroendocrine system resulted in a further increase of plasma renin and corticosterone levels as well as blood pressure and adrenal weight. These effects together with accelerated mortality and increased pathology indicate that chronic consumption of caffeinated liquids adds to the risks of psychosocial stress.     

Variability in caffeine consumption from coffee and tea: possible significance for epidemiological studies

Five surveys, using a previously developed high-performance liquid chromatography procedure to measure caffeine concentrations, indicated great variations in the concentrations of caffeine in tea and coffee. In the study of beverages prepared at home, data on caffeine concentrations in 58 samples of tea and coffee, volumes of cups, and numbers of cups consumed/day, indicated that the range of caffeine intakes for the women participating was 49-1022 mg/day. There were considerable day-to-day variations in caffeine contents in coffee samples from some commercial coffee shops. When 17 samples of five national brands of instant coffee were made into beverages in the laboratory, variations in caffeine concentrations between lots were small but between brands were significant. A considerable range of caffeine concentrations was also found when 12 samples of coffee prepared at work by different individuals using the same jar of instant coffee were analysed. Analysis of tea samples prepared in the laboratory indicated that steeping time had an important influence on resulting caffeine and theobromine concentrations. People preparing their own beverages were found to drink more liquid than the volume offered commerically. The mean caffeine 'contents' of home-made coffee and of coffee prepared by individuals at work were 79.4 and 81.7 mg/cup respectively, indicating a mean intake of approximately 80 mg caffeine/cup. When this amount (80 mg/cup) was used to estimate daily intakes of caffeine from coffee, on the basis of the number of reported cups/day, and the values obtained were compared with the amounts actually consumed by individuals, the potential for misrepresentation of individual consumption became obvious. For example, for subjects consuming three cups of coffee, only 25% would have been correctly categorized in the expected range for the daily intake of caffeine, 39% would have been overestimated and 36% underestimated for the amount of caffeine consumed. These variations in caffeine concentrations and in the volume of coffee consumed have frequently been ignored in examinations of the possible relationship between coffee consumption and various health problems, and this could perhaps partly explain some conflicting results seen in epidemiological studies.     

Effects of Caffeine and Noise on Mood,Performance and Cardiovascular Functioning

An experiment was conducted to examine the effects of caffeine and noise on mood, mental performance and cardiovascular function. One hundred and six young adults (mean age 21·2 years) took part in the study. Subjects were assigned to one of six groups formed by combining noise/quiet and drink (caffeinated coffee, decaffeinated coffee and fruit juice) conditions. Subjects were familiarized with the tasks and then completed a pre-drink baseline session (conducted in the quiet). Subjects were then given either caffeinated coffee (1·5 mg/kg caffeine), decaffeinated coffee or fruit juice. Following consumption of the drink subjects were re-tested 1 h later, either in noise (75 dBA conglomerate noise, consisting of speech, music and machinery noise) or in quiet. The subjects exposed to noise felt more anxious and showed an increase in blood pressure. Their performance of a cognitive vigilance task also declined over time. There were no significant main effects of caffeine, although simple reaction time was quickest in the caffeinated coffee group. Caffeine did not modify the effects of noise on mood, cardiovascular functioning or sustained attention. Indeed, the only interaction between drinks and noise was found in recall and recognition memory tasks, with the caffeine/noise group having better memory performance than the decaffeinated/noise subjects. Overall, the results show that low levels of caffeine do not increase the behavioural and physiological changes observed in a stressful situation. © 1997 John Wiley & Sons, Ltd.     

Coffee drinking and cigarette smoking: II. coffee, urinary pH and cigarette smoking behavior

Two experiments designed to assess the relationship between coffee intake and smoking are reported. In Experiment I, coffee drinking smokers were randomly assigned to four groups in which they received 0, 1, 2, or 3 cups of coffee during two one-hour sessions while they worked on crossword puzzles. Results showed that subjects receiving coffee in any amount smoked more than subjects who were not provided coffee. Moderate and low rate smokers were then randomly assigned to one of five groups in Experiment II, in which they were provided no drink, water, Postum^® (a coffee substitute), caffeinated, or decaffeinated coffee. These groups were selected to assess the characteristics of coffee that may have influenced increased smoking. Results for number of cigarettes smoked and puff rate generally showed that subjects receiving caffeinated or decaffeinated coffee smoked more than subjects in the no drink or water control groups. The results of this study provide experimental evidence of the role of coffee in setting the occasion for smoking, as well as ruling out the presence of a liquid or caffeine as the important characteristics of coffee in influencing smoking.     

Chronic coffee and caffeine ingestion effects on the cognitive function and antioxidant system of rat brains

Coffee is a popular beverage consumed worldwide and its effect on health protection has been well studied throughout literature. This study investigates the effect of chronic coffee and caffeine ingestion on cognitive behavior and the antioxidant system of rat brains. The paradigms of open field and object recognition were used to assess locomotor and exploratory activities, as well as learning and memory. The antioxidant system was evaluated by determining the activities of glutathione reductase (GR), glutathione peroxidase (GPx) and superoxide dismutase (SOD), as well as the lipid peroxidation and reduced glutathione content. Five groups of male rats were fed for approximately 80 days with different diets: control diet (CD), fed a control diet; 3% coffee diet (3%Co) and 6% coffee diet (6%Co), both fed a diet containing brewed coffee; 0.04% caffeine diet (0.04%Ca) and 0.08% caffeine diet (0.08%Ca), both fed a control diet supplemented with caffeine. The estimated caffeine intake was approximately 20 and 40 mg/kg per day, for the 3%Co-0.04%Ca and 6%Co-0.08%Ca treatments, respectively. At 90 days of life, the animals were subjected to the behavioral tasks and then sacrificed. The results indicated that the intake of coffee, similar to caffeine, improved long-term memory when tested with object recognition; however, this was not accompanied by an increase in locomotor and exploratory activities. In addition, chronic coffee and caffeine ingestion reduced the lipid peroxidation of brain membranes and increased the concentration of reduced-glutathione. The activities of the GR and SOD were similarly increased, but no change in GPx activity could be observed. Thus, besides improving cognitive function, our data show that chronic coffee consumption modulates the endogenous antioxidant system in the brain. Therefore, chronic coffee ingestion, through the protection of the antioxidant system, may play an important role in preventing age-associated decline in the cognitive function.     

Coffee drinking and cigarette smoking: I. coffee,caffeine and cigarette smoking behavior

Two experiments designed to assess the relationship between coffee intake and smoking are reported. In Experiment I, coffee drinking smokers were randomly assigned to four groups in which they received 0, 1, 2, or 3 cups of coffee during two one-hour sessions while they worked on crossword puzzles. Results showed that subjects receiving coffee in any amount smoked more than subjects who were not provided coffee. Moderate and low rate smokers were then randomly assigned to one of five groups in Experiment II, in which they were provided no drink, water, Postum^® (a coffee substitute), caffeinated, or decaffeinated coffee. These groups were selected to assess the characteristics of coffee that may have influenced increased smoking. Results for number of cigarettes smoked and puff rate generally showed that subjects receiving caffeinated or decaffeinated coffee smoked more than subjects in the no drink or water control groups. The results of this study provide experimental evidence of the role of coffee in setting the occasion for smoking, as well as ruling out the presence of a liquid or caffeine as the important characteristics of coffee in influencing smoking.     

The effect of brewed and instant coffee on reproduction and teratogenesis in the rat

A blend of roasted and ground coffees was brewed and an instant coffee was prepared daily and given to rats in place of their drinking water, at either full-strength (100%) or as 50 or 25% dilutions. A control group was given water. The administration of the coffee solutions began shortly after weaning and continued for about 30 weeks, through two pregnancies. During pregnancy and lactation the caffeine intakes were approximately 80, 40, or 20 mg/kg/day, being slightly higher in the groups given brewed coffee and slightly lower in the groups give instant coffee. The parent rats given either brewed or instant coffee grew as well as or better than controls and ate more feed, although feed efficiencies were not different. The rats given full-strength coffees drank significantly less than controls, but the ones given 50 or 25% solutions drank more. Both male and female rats given 100% brewed or instant coffee to replace their drinking water had enlarged kidneys at 13 and 30 weeks, while only the females given 50% solutions of either coffee had enlarged kidneys. The females given full-strength coffees had enlarged livers at both times, while the females given 50% brewed coffee had enlarged livers only at 30 weeks. No effects on the organ weights were seen in the groups given 25% coffee solutions. No effects were seen on reproduction or lactation, except that the pups in the groups given 100% brewed or instant coffee to replace their drinking water weighed significantly less than the controls at weaning. Neither embryotoxicity nor frank teratogenicity was seen as a result of coffee ingestion. However, the fetuses in the groups given 100 or 50% solutions of the brewed coffee and 100% instant coffee in place of drinking water had a significantly higher incidence of unossified sternebrae, indicating a delay in calcification.     

Sex differences in estimation of time intervals and in reaction time are removed by moderate but not high doses of caffeine in coffee

Estimation of the passage of time in the seconds-to-minutes range and reaction time are strongly dependent on a hypothetical internal clock. Dopamine is the neurotransmitter most closely related to the rate of this clock. Caffeine, probably the most consumed drug in the world, leads to an augmentation of dopamine neurotransmission. In this study coffee, which reproduces the conditions under which caffeine is normally ingested, containing 3, 75, 150 or 300 mg of caffeine, was given to healthy male and female volunteers. A computerized time estimation and reaction time test was carried out 50 min after ingestion. Sex differences in placebo control subjects (who took decaffeinated coffee with 3 mg of caffeine), with females making more accurate estimates of time intervals than males and males showing shorter reaction times than females, were removed in subject taking doses of 75 and 150 mg of caffeine in the case of time estimation and 150 mg in the case of reaction time. The 300 mg dose induced overestimation of time in females and shortened the reaction time in males. There were no sex differences in the pharmacokinetics of caffeine, as measured in salivary concentration of caffeine using high-performance liquid chromatography. Results indicating sex differences in time estimation or reaction time should not be generalized from the laboratory to real life without considering the fact that everyday coffee consumption may eliminate these differences. Copyright 2001 John Wiley & Sons, Ltd.     

Expectations and placebo responses to caffeine-associated stimuli

Rationale To test the theory that expectations control placebo responses. Objective Subjects (n=20) were asked how much they expected their arousal to increase after one or two cups of coffee, and were subsequently exposed to one or two cups of decaffeinated coffee, or to caffeine equivalent to one or two cups of coffee (200 and 400 mg). The expectancy theory of placebo responses predicts a positive correlation between expectations and actual placebo responses. Methods Dependent variables were acoustic startle eyeblink and skin conductance responses, blood pressure and heart rate, and measures of subjective arousal. Results Caffeine increased startle eyeblink and skin conductance responses, as well as blood pressure and subjective arousal. Decaffeinated coffee increased startle eyeblink and skin conductance responses, but had no effect on subjective arousal, although the participants clearly expected increased subjective arousal after both one and two cups of coffee. However, there were significant correlations between the alertness expected after coffee, and the actual alertness recorded after decaffeinated coffee. Conclusions The main finding in this study was that relatively strong expectations about the effects of coffee did not generate placebo responses after administration of decaffeinated coffee. Expectations were dose dependent, whereas the placebo response was not. However, expected alertness after coffee predicted recorded alertness after coffee. In sum, the expectancy theory of placebo effects received only limited support.     

The acute physiological and mood effects of tea and coffee: the role of caffeine level

The objective of this study was to determine the effect of caffeine level in tea and coffee on acute physiological responses and mood. Randomised full crossover design in subjects after overnight caffeine abstention was studied. In study 1 (n = 17) the caffeine level was manipulated naturalistically by preparing tea and coffee at different strengths (1 or 2 cups equivalent). Caffeine levels were 37.5 and 75 mg in tea, 75 and 150 mg in coffee, with water and no-drink controls. In study 2 (n = 15) caffeine level alone was manipulated (water, decaffeinated tea, plus 0, 25, 50, 100, and 200 mg caffeine). Beverage volume and temperature (55 degrees C) were constant. SBP, DBP, heart rate, skin temperature, skin conductance, and mood were monitored over each 3-h study session. In study 1, tea and coffee produced mild autonomic stimulation and an elevation in mood. There were no effects of tea vs. coffee or caffeine dose, despite a fourfold variation in the latter. Increasing beverage strength was associated with greater increases in DBP and energetic arousal. In study 2, caffeinated beverages increased SBP, DBP, and skin conductance and lowered heart rate and skin temperature compared to water. Significant dose-response relationships to caffeine were seen only for SBP, heart rate, and skin temperature. There were significant effects of caffeine on energetic arousal but no consistent dose-response effects. Caffeinated beverages acutely stimulate the autonomic nervous system and increase alertness. Although caffeine can exert dose-dependent effects on a number of acute autonomic responses, caffeine level is not an important factor. Factors besides caffeine may contribute to these acute effects.     

Coffee contains cholinomimetic compound distinct from caffeine. I: Purification and chromatographic analysis

Both regular and decaffeinated coffees were found to have cholinomimetic actions when tested in urethane-anesthetized rats. These actions were distinct from those of caffeine and reversible by atropine. The bioactive fraction was purified from alcoholic extracts of instant decaffeinated coffee by liquid column chromatography and preparative TLC. The purified compound showed similar pharmacological actions as the starting material. Chromatographic behavior was further characterized by analytical TLC and HPLC. Chromatographic analyses of extracts of green coffee beans and roasted ground coffees showed that the cardioactive compound was only present in roasted coffees. Similar analyses of other commonly consumed beverages, including teas and cocoa, showed that this compound was not present in beverages besides coffee.     

The cardiovascular effects of regular and decaffeinated coffee.

In a single-blind study the effects of drinking two cups of regular or decaffeinated coffee on blood pressure, heart rate, forearm blood flow and plasma concentrations of caffeine, renin and catecholamines were studied in 12 normotensive subjects. Drinking regular coffee led to a rise of blood pressure, a fall of heart rate and an increase of plasma catecholamines. Decaffeinated coffee induced a smaller increase of diastolic blood pressure without changing other parameters. This study shows that the cardiovascular effects of drinking coffee are mainly the result of its caffeine content.     

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.