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.     

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. Received: 16 February 1999 / Final version: 20 December 1999     

The effects of black tea and other beverages on aspects of cognition and psychomotor performance

Nineteen healthy volunteers ingested 400 ml black tea, coffee, caffeinated water, decaffeinated tea or plain water on three occasions through the day (0900, 1400 and 1900 hours). A 2 × 2 factorial design with caffeine (0, 100 mg) and beverage type (water, tea) was employed, with coffee (100 mg caffeine) as a positive internal control, based on a five-way crossover. A psychometric test battery comprising critical flicker fusion (CFF), choice reaction time (CRT), short-term memory (STM) and subjective sedation (LARS) was performed at regular intervals throughout the day, and intensively so immediately following each beverage. Consumption of tea compared to water was associated with transient improvements in performance (CFF) within 10 min of ingestion and was not affected by the time of day. Caffeine ingestion was associated with a rapid (10 min) and persistent reduction in subjective sedation values (LARS), again independent of time of day, but did not acutely alter CFF threshold. Over the whole day, consumption of tea rather than water, and of caffeinated compared to decaffeinated beverages, largely prevented the steady decline in alertness (LARS) and cognitive capacity observed with water ingestion. The effects of tea and coffee were similar on all measures, except that tea consumption was associated with less variation in CFF over the whole day. No significant treatment effects were apparent in the data for the STM. Tea ingestion is associated with rapid increases in alertness and information processing capacity and tea drinking throughout the day largely prevents the diurnal pattern of performance decrements found with the placebo (no caffeine) condition. It appears that the effects of tea and coffee were not entirely due to caffeine per se; other factors either intrinsic to the beverage (e.g. sensory attributes or the presence of other biologically active substances) or of a psychological nature (e.g. expectancy) are likely to play a significant role in mediating the responses observed in this study. Received: 18 September 1997/Final version: 16 February 1998     

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.     

Does caffeine intake enhance absolute levels of cognitive performance?

The relationship between habitual coffee and tea consumption and cognitive performance was examined using data from a cross-sectional survey of a representative sample of 9003 British adults (the Health and Lifestyle Survey). Subjects completed tests of simple reaction time, choice reaction time, incidental verbal memory, and visuo-spatial reasoning, in addition to providing self-reports of usual coffee and tea intake. After controlling extensively for potential confounding variables, a dose-response trend to improved performance with higher levels of coffee consumption was observed for all four tests (P<0.001 in each case). Similar but weaker associations were found for tea consumption, which were significant for simple reaction time (P=0.02) and visuo-spatial reasoning (P=0.013). Estimated overall caffeine consumption showed a dose-response relationship to improved cognitive performance (P<0.001 for each cognitive test, after controlling for confounders). Older people appeared to be more susceptible to the performance-improving effects of caffeine than were younger. The results suggest that tolerance to the performance-enhancing effects of caffeine, if it occurs at all, is incomplete.     

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.     

Stimulatory effect of oral administration of tea, coffee or caffeine on UVB-induced apoptosis in the epidermis of SKH-1 mice

Oral administration of green tea or a caffeine solution, but not decaffeinated green tea, inhibits UVB-induced complete carcinogenesis in SKH-1 mice. Oral administration of green tea, coffee or a caffeine solution for 2 weeks enhanced UVB-induced increases in apoptosis in the epidermis, but these treatments had no effect in non-UVB treated normal epidermis. Our results suggest that administration of green tea, coffee and caffeine may inhibit UVB-induced carcinogenesis--at least in part--by enhancing UVB-induced apoptosis. Plasma levels of caffeine observed after its oral administration at cancer-preventive dose levels were within the range observed in moderate coffee drinkers. Topical applications of caffeine to mice previously treated with UVB for 20 weeks (high risk mice without tumors) inhibited the formation of tumors and stimulated apoptosis in the tumors but not in areas of the epidermis away from tumors. The selective effects of caffeine administration to stimulate UVB-induced apoptosis or apoptosis in tumors but not in normal epidermis or in areas of the epidermis away from tumors is of considerable interest, but the reasons for the selective effects of caffeine on apoptosis in DNA damaged tissues are unknown. Further studies are needed to determine mechanisms of these effects of caffeine and to determine the effects of caffeine administration on sunlight-induced actinic keratoses and squamous cell carcinomas in humans.     

Caffeine-associated stimuli elicit conditioned responses: an experimental model of the placebo effect

Rationale: A neutral stimulus repeatedly paired with administration of a drug may elicit a conditioned response. This process, termed pharmacological classical conditioning, may be important in the understanding of placebo effects. Objective: The unconditioned response to caffeine is increased physiological and psychological arousal. The present study investigated whether stimuli associated with the use of caffeine, i.e. the smell and taste of coffee, elicited a conditioned increase in arousal. It was also investigated whether conditioned arousal modulated the unconditioned arousal induced by caffeine. Methods: Twenty subjects who drank at least two cups of coffee per day were exposed to four conditions in a within-subjects design, where the subjects received coffee or orange juice crossed with placebo or 2 mg/kg caffeine. Dependent variables were skin conductance responses and startle reflexes to 85 dB noise bursts, skin conductance levels, blood pressure, heart rate, and subjective measures of arousal. Results: Both caffeine (caffeinated juice) and caffeine-associated stimuli (decaffeinated coffee) increased subjective and physiological arousal. When caffeine and caffeine-associated stimuli were presented together (caffeinated coffee), a non-significant tendency towards an additive effect of the conditioned arousal on the unconditioned arousal to caffeine was seen in some dependent variables. Conclusions: Presentation of caffeine-associated stimuli to caffeine-users elicited conditioned responses similar to the unconditioned drug response. Thus, presentation of caffeine-associated stimuli could be used as an experimental model of placebo effects. Received: 23 November 1998/Final version: 16 February 1999     

Effects of hot tea, coffee and water ingestion on physiological responses and mood: the role of caffeine, water and beverage type

Psychopharmacological studies using caffeinated beverages or caffeine have rarely considered temporal effects on psychological and physiological function or the specific contribution of caffeine, hot water, or beverage type to the observed effects. The effect of 400 ml hot tea, coffee, and water consumption on systolic and diastolic blood pressure (SBP and DBP), heart rate, skin conductance (a measure of sympathetic nervous system activation), skin temperature, salivary cortisol, and mood were monitored in 16 healthy caffeine-withdrawn (14 h) subjects in a complete crossover design. Beverages were ingested with/without 100 mg caffeine and milk (tea/coffee only). Hot beverage ingestion rapidly increased skin conductance and temperature (+1.7°C) with peak effects observed only 10–30 min post-consumption. Caffeine in the beverage rapidly augmented skin conductance responses but, in contrast to the effect of hot water, reduced the skin temperature response and increased SBP (+2.8 mmHg) and DBP (+2.1 mmHg) 30–60 min post-consumption. Both caffeine and milk addition to beverages independently improved mood and reduced anxiety 30 and 60 min post-consumption. Milk addition had no other effects apart from attenuating the transient increase in physiological responses associated with the drinking phase. There were no effects of beverage consumption on salivary cortisol or of beverage vehicle on salivary caffeine levels, the latter indicating that caffeine pharmacokinetics was similar in both tea and coffee, and not different from caffeinated water. In keeping with this, the responses to tea and coffee ingestion were similar and largely accounted for by the effects of hot water and caffeine. However, tea potentiated the increase in skin temperature compared to coffee and water indicative of a greater vasodilatory response plausibly related to the presence of flavonoids in tea. We conclude that ingestion of hot caffeinated beverages stimulates physiological processes faster than hitherto described, primarily via the effects of hot water and caffeine, but with beverage type and milk playing important modulatory roles. Received: 15 March 1997/Final version: 23 May 1997     

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.     

Beliefs,Behaviors, and Contexts of Adolescent Caffeine Use: A Focus Group Study

Background: Caffeinated products are widely available to adolescents, and consumption of caffeine products—energy drinks and coffee in particular—is on the rise in this age group (Branum, Rossen, & Schoendorf, 2014). Yet, little is known about the psychosocial context of caffeine use. Previous studies on adolescent caffeine use have focused on caffeine's acute physiological effects, rather than the psychosocial contexts and beliefs regarding different types of caffeinated beverages (e.g., coffee, energy drinks, soda). Objectives: The current research examines the contexts and beliefs associated with adolescents' use of caffeinated beverages (e.g., coffee, energy drinks, soda) using a focus group approach. Methods: Eleven focus group interviews (49 total participants) addressed adolescents' motivations for and patterns of caffeine use; they were transcribed and axial coding was used to identify common themes. Results: Coffee and energy drinks were perceived to be the most popular caffeinated beverages. Reasons for consuming caffeine included the effect of caffeine as a stimulant, the pleasant feelings experienced when drinking it, and the fact that caffeine was available. As for contexts, coffee was consumed in more diverse social contexts than other caffeinated beverages. Friends and sports were the most popular contexts for energy drink use. Conclusions: The present findings inform adolescent health promotion efforts and provide researchers and practitioners alike detailed information in adolescents' own words about how and why they use caffeine. Adolescents' beliefs about caffeinated products are not uniform; the reasons adolescents articulate regarding their use of coffee, soda, and energy drinks are different across contexts and beverage type.     

Coffee and cardiovascular disease: in vitro, cellular, animal, and human studies.

Coffee is a commonly consumed beverage with potential health benefits. This review will focus on cardiovascular disease. There are three preparations of coffee that are commonly consumed and thus worthy of examination; boiled unfiltered coffee, filtered coffee, and decaffeinated coffee. Coffee has over a thousand chemicals, many formed during the roasting process. From a physiological point of view, the potential bioactives are caffeine, the diterpenes cafestol and kahweol found in the oil, and the polyphenols, most notably chlorogenic acid. We will examine coffee and its bioactives and their connection with and effect on the risk factors which are associated with heart disease such as lipids, blood pressure, inflammation, endothelial function, metabolic syndrome and potentially protective in vivo antioxidant activity. These will be critically examined by means of in vitro studies, cell experiments, animal supplementation, epidemiology, and the most definitive evidence, human trials.     

White wine and beer induce gastro-oesophageal reflux in patients with reflux disease

BACKGROUND: An induction of gastro-oesophageal reflux has been reported after ingestion of alcoholic beverages in healthy volunteers. However, it is unknown whether reflux in gastro-oesophageal reflux disease patients will be enhanced by the ingestion of alcoholic beverages. AIM: To investigate the effects of wine and beer on postprandial reflux in reflux patients. METHODS: Twenty-five patients (reflux oesophagitis 15, non-erosive reflux disease 10; 18 men and seven women) drank 300-mL white wine (n = 17), 500-mL beer (n = 8), or identical amounts of tap water (controls) together with a standardized meal in a randomized order. pH-measurement was carried out during three postprandial hours by pH-metry and the percentage of time pH < 4 was calculated. RESULTS: Both alcoholic beverages increased reflux compared with water [wine 23% (median), water 12%, P < 0.01; beer 25%, water 11%, P < 0.05]. Between wine and beer, no difference in reflux induction was obtained. The reflux induction was seen in patients with (23%, P < 0.01) and without reflux oesophagitis (22%, P < 0.05) and in both sexes (women 23%, men 25%, P < 0.05 each). CONCLUSIONS: Ingestion of commonly consumed alcoholic beverages such as wine and beer induces gastro-oesophageal reflux in gastro-oesophageal reflux disease patients. Therefore, these patients should be advised to avoid the intake of large amounts (> or = 300 mL) of these beverages.     

Effects of coffee on driving performance during prolonged simulated highway driving

Rationale

Coffee is often consumed to counteract driver sleepiness. There is limited information on the effects of a single low dose of coffee on prolonged highway driving in non-sleep deprived individuals.

Objectives

The aim of this study was to examine the effects of a single cup of coffee (80?mg caffeine) on simulated highway driving performance.

Methods

Non-sleep deprived healthy volunteers (n?=?24) participated in a double-blind, placebo-controlled, crossover study. After 2?h of monotonous highway driving, subjects received caffeinated or decaffeinated coffee during a 15-min break before continuing driving for another 2?h. The primary outcome measure was the standard deviation of lateral position (SDLP), reflecting the weaving of the car. Secondary outcome measures were speed variability, subjective sleepiness, and subjective driving performance.

Results

The results showed that caffeinated coffee significantly reduced SDLP as compared to decaffeinated coffee, both in the first (p?=?0.024) and second hour (p?=?0.019) after the break. Similarly, the standard deviation of speed (p?=?0.024; p?=?0.001), mental effort (p?=?0.003; p?=?0.023), and subjective sleepiness (p?=?0.001; p?=?0.002) were reduced in both the first and second hour after consuming caffeinated coffee. Subjective driving quality was significantly improved in the first hour after consuming caffeinated coffee (p?=?0.004).

Conclusions

These findings demonstrate a positive effect of one cup of caffeinated coffee on driving performance and subjective sleepiness during monotonous simulated highway driving.     

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.     

Behavioral effects of nicotine, amphetamine and cocaine under a fixed-interval schedule of food reinforcement in rats chronically exposed to caffeine

 Epidemiological surveys demonstrate that caffeine, the main psychoactive ingredient of coffee, is a positive correlate in drug abuse. To characterize the behavioral nature of caffeine interactions with other psychomotor stimulants, we examined the effects of chronic caffeine exposure on the behavioral responses to nicotine, amphetamine, cocaine, the selective D₁ agonist SKF-82958 and the selective D₂ receptor agonist NPA, in rats responding under a fixed interval (FI) schedule of food reinforcement. Following stabilization of rates and temporal patterns of responding (mathematically expressed as quarter-life values, QL), twenty-one Sprague-Dawley rats responding under a 5-min FI schedule of food reinforcement were divided into two groups; one (twelve rats) maintained on tap water (control) and the other (nine rats) on caffeine (3 mg/ml added to the drinking water). Following the substitution of caffeine solution for tap water, behavior was temporarily disrupted as evidenced by decreases in responding and QL values which reached a maximum after 72 h (rate 60% and QL 30% below baseline levels). Rats developed complete tolerance to these effects of caffeine over 5 days of caffeine exposure. After response rate and QL values stabilized, effects of drugs were evaluated. Nicotine (0.01–1.0 mg/kg; SC), amphetamine (0.1–5.6; IP), and cocaine (1.0–17; IP) each produced biphasic dose-dependent changes in response rate with maximum increases in response rate following intermediate doses and decreases in response rates following higher doses. The increase in rates of responding produced by amphetamine or cocaine (but not nicotine) were greater (P<0.05) in caffeine-drinking than in water-drinking rats. Both SKF-82958 (0.001–0.3 mg/kg; IP) and NPA (0.0001–0.1; IP) produced only dose-dependent decreases in rates of responding. Caffeine-drinking rats were less sensitive to the rate-depressant effects of SKF-82958 (P<0.05) than water-drinking rats. However, similar changes (P>0.05) were produced by NPA in both groups. Except for amphetamine, the remaining drugs produced similar (P>0.05) dose-dependent decreases in QL values in water- and caffeine-drinking rats. Amphetamine produced smaller decreases in QL values in caffeine-drinking rats than in water-drinking rats (P<0.05). Chronic exposure to caffeine produced complete insurmountable tolerance to the response-rate increasing (stimulant) effects of acute caffeine (3.0–17 mg/kg; IP) in caffeine-drinking rats. In conclusion, our study revealed that chronic caffeine exposure potentiates the behavioral response to amphetamine and cocaine but not to that of nicotine in rats responding under a FI schedule of food reinforcement. Thus, it is likely that these effects are mediated through different pharmacological mechanisms. Received: 3 September 1997 / Final version: 9 May 1998     

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.     

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.     

Effect of caffeine-free beverages on elderly hospitalised patients

The objectives of the study were to determine whether, by providing caffeine-free tea and coffee, plasma caffeine concentrations would fall in elderly hospitalised patients, and whether, as a result, sleep profiles and urinary incontinence would be altered. Twenty-eight patients in two wards of an elderly care hospital received caffeine-containing or caffeine-free tea and coffee for consecutive three week periods in a study which was blinded to patients, nurses and investigator. Median caffeine concentration (μg/ml) was stable between the run in period at 2.3 (range 0–5.8) and the caffeine-containing period at 1.6 (range 0.4–6.0), but fell significantly to 0 (range 0–0.7), during the caffeine-free period (P<0.001). In spite of significantly lowered caffeine concentrations, no change in sleep patterns or urinary incontinence was noted. Of 12 patients with sleep problems a benefit to sleep quality was reported by two individuals, one of whom was prescribed hypnotics from which she subsequently successfully withdrew.