Studies of Caffeine & Coffee Drinking
Lane, J.D., Barkauskas, C.E., Surwit, R.S., and Feinglos, M.N. Caffeine impairs glucose metabolism in type 2 diabetes. DIABETES CARE, 2004, 27: 2047-2048.
Objective: Caffeine is a widely consumed central stimulant that has recently been shown to decrease insulin sensitivity in healthy, non-diabetic individuals. We hypothesized that caffeine disrupts glucose metabolism in patients with type 2 diabetes and causes both hyperinsulemia and hyperglycemia.
Research Design and Methods. A placebo-controlled cross-over study tested the effects of a moderate dose of caffeine (375 mg) on fasting glucose and insulin and on glucose and insulin responses to a mixed carbohydrate meal in 14 adult men and women diagnosed with type 2 diabetes. Responses to the meal were calculated as incremental areas under the 2-hour glucose and insulin time-curves.
Results. Caffeine had no effect on fasting levels of glucose or insulin, but significantly increased the glucose (21% larger) and insulin (48% larger) responses to the mixed meal.
Conclusions. Caffeine can cause exaggerated hyperglycemia and hyperinsulinemia in patients with type 2 diabetes, when given prior to a meal. The increase in post-prandial glucose could impede clinical efforts at glucose control in patients who consume caffeine on a daily basis. Long term effects on diabetes and its complications remain to be determined.
Lane, J. D., Pieper, C. F., Phillips-Bute, B. G., Bryant, J. E., Kuhn, C. M.. (2002). "Caffeine affects cardiovascular and neuroendocrine activation at work and home." Psychosomatic Medicine. 64(4): 595-603.
OBJECTIVE: This study investigated the effects of moderate doses of caffeine on ambulatory blood pressure and heart rate, urinary excretion of epinephrine, norepinephrine, and cortisol, and subjective measures of stress during normal activities at work and at home in the evening. METHODS: Healthy, nonsmoking, habitual coffee drinkers (N = 47) participated in 3 days of ambulatory study. After a day of ad lib caffeine consumption, caffeine (500 mg) and placebo were administered double-blind in counter-balanced order on separate workdays. Ambulatory blood pressure and heart rate were monitored from the start of the workday until bedtime. Urinary excretion of catecholamines and cortisol was assessed during the workday and evening. RESULTS: Caffeine administration significantly raised average ambulatory blood pressure during the workday and evening by 4/3 mm Hg and reduced average heart rate by 2 bpm. Caffeine also increased by 32% the levels of free epinephrine excreted during the workday and the evening. In addition, caffeine amplified the increases in blood pressure and heart rate associated with higher levels of self-reported stress during the activities of the day. Effects were undiminished through the evening until bedtime. CONCLUSIONS: Caffeine has significant hemodynamic and humoral effects in habitual coffee drinkers that persist for many hours during the activities of everyday life. Furthermore, caffeine may exaggerate sympathetic adrenal-medullary responses to the stressful events of normal daily life. Repeated daily blood pressure elevations and increases in stress reactivity caused by caffeine consumption could contribute to an increased risk of coronary heart disease in the adult population.
Lane, J. D. and Phillips-Bute, B. G. (1998). "Caffeine deprivation affects vigilance performance and mood." Physiology & Behavior, 63(1):171-175.The effects of brief caffeine deprivation on vigilance performance, mood, and symptoms of caffeine withdrawal were studied in habitual coffee drinkers. Thirty male and female coffee drinkers were tested twice at midday (1130 to 1330 hrs) after mornings in which they either consumed caffeinated beverages ad lib or abstained. Vigilance performance was tested with a 30-min computerized visual monitoring task. Mood and withdrawal symptom reports were collected by questionnaire. Caffeine deprivation was associated with impaired vigilance performance characterized by a reduction in the percentage of targets detected and an increase in response time, and by subjective reports of decreased vigor and increased fatigue and symptoms characterized by sleepiness, headache, and reduced ability to work. Even short periods of caffeine deprivation, equivalent in length to skipping regular morning coffee, can produce deficits in sustained attention and noticeable unpleasant caffeine-withdrawal symptoms in habitual coffee drinkers. Such symptoms my be a common side-effect of habitual caffeine consumption that contributes to the maintenance of this behavior.
Lane, J. D., Phillips-Bute, B. G., and Pieper, C. F. (1998). "Caffeine raises blood pressure at work." Psychosomatic Medicine, 60(3): 327-330.Objective: The study investigated the effects of moderate doses of caffeine on ambulatory blood pressure and heart rate during workday activities. Methods: Healthy, nonsmoking, habitual coffee drinkers (N = 21) received daily doses of 100 mg and 500 mg of caffeine on 2 days in a crossover design. Treatment order was random and counterbalanced, and administration was double-blind. Ambulatory monitoring was conducted for 6 to 9 hours during normal workday activities and diary entries were completed at each measurement. Ambulatory data were analyzed for the effects of caffeine dose, controlling for variations in posture, physical activity, and perceived stress. Results: The average workday blood pressure and heart rate were significantly higher when the higher dose of caffeine was consumed. Controlling for other factors, dose-related differences were 4 mm Hg for systolic and 3 mm Hg for diastolic blood pressure, and were 3 bpm for heart rate. Conclusions: Results support earlier evidence that caffeine raises blood pressure at work, and demonstrate that these presser effects are independent of changes in posture, physical activity, or stress. Daily blood pressure increases associated with caffeine consumption could increase the risk of developing cardiovascular diseases. In addition, caffeine consumption effects might confound ambulatory investigations of the cardiovascular effects of other psychosocial, personality, or health-behavior factors.
Phillips-Bute, B. G. and Lane, J. D. (1997). "Caffeine withdrawal symptoms following brief caffeine deprivation." Physiology & Behavior 63(1): 35-9.The effects of short-term caffeine deprivation on mood, withdrawal symptoms and psychomotor performance were studied in habitual coffee drinkers. Thirty-one male and female coffee drinkers were tested twice at midday (1130 to 1330 h) 4 h after double-blind administration of 250 mg of caffeine or placebo. Mood and withdrawal symptoms reports were collected by questionnaires. Psychomotor performance was tested with a brief computerized test battery, and causal blood pressure was measured. Caffeine deprivation was associated with decreased vigor and increased fatigue and with symptoms including sleepiness and yawning. Blood pressure was lower by 5-6 mm Hg. No changes in psychomotor performance were observed. Even short periods of caffeine deprivation, equivalent in length to missing regular morning coffee, can produce noticeable unpleasant caffeine withdrawal symptoms in habitual coffee drinkers. Such symptoms may be common side effects of habitual caffeine consumption that contribute to the maintenance of this behavior.
Lane, J. D. (1997). "Effects of brief caffeinated-beverage deprivation on mood, symptoms, and psychomotor performance." Pharmacology, Biochemistry & Behavior 58(1): 203-8.The effects of short-term deprivation of caffeinated beverages on mood, withdrawal symptoms, and psychomotor performance were studied in habitual coffee drinkers. Twenty-four male and female coffee drinkers were tested at midday (1130-1330 h) under two conditions. On one day they consumed caffeinated beverages ad lib prior to testing, and on the other they remained caffeine abstinent. The order of treatments was counterbalanced. Mood and withdrawal symptom reports were collected by questionnaires. Psychomotor performance was tested with a computerized test battery. Caffeinated-beverage deprivation was associated with decreased vigor and increased fatigue and with symptoms including headache. No changes in psychomotor performance were observed. Even short periods of caffeinated-beverage deprivation, equivalent in length to missing regular morning coffee, can produce noticeable unpleasant caffeine-withdrawal symptoms by the middle of the day. These symptoms may be a common side effect of habitual caffeinated beverage consumption.
Lane, J. D. (1996). "Association of coffee drinking with cigarette smoking in the natural environment." Experimental & Clinical Psychopharmacology. 4(4), 409-412.Coffee drinking may serve as a cue for cigarette smoking. The associationof coffee drinking and cigarette smoking in the natural environment was studied in 6 participants who recorded every instance of ad lib cigarette smoking and coffee drinking for 4 consecutive days. The rate of cigarette smoking was higher during intervals associated with coffee drinking (2.4 cigarettes/hr) than at other times of the day (1.0 cigarettes/hr).However, diary records revealed that on average only 14% of cigarettes were smoked while drinking coffee, and only 55% of coffee-drinking events were accompanied by cigarettes. These results suggest that coffee drinking may exert some stimulus control over smoking in the natural environment. However, given the limited number of coffee-drinking episodes compared with cigarettes consumed in a day, the contributions of coffee drinking to maintaining smoking behavior are probably minimal.
Lane, J. D. and Rose, J. E. (1995). "Effects of daily caffeine intake on smoking behavior in the natural environment." Experimental & Clinical Psychopharmacology, 3: 49-55.The effects of changes in daily caffeine intake on cigarette smoking were investigated. Forty cigarette smokers consumed caffeine ad lib on a baseline day then consumed controlled multiple doses of caffeine (100 mg and 500 mg per day) for two-day trials. Smokers recorded the number of cigarettes consumed, and measurements of expired-air carbon monoxide and salivary cotinine concentration were obtained to estimate smoke and nicotine intake. Baseline caffeine intake averaged 449 mg per day, with wide variations among participants. The 5-fold change in caffeine dose on treatment days did not affect any measure of smoking behavior in these participants. Results suggest that daily caffeine intake has little influence on cigarette smoking in the natural environment. Coffee drinking and cigarette smoking are commonly associated behaviors, although the links between them are not yet understood. Results raise doubts that the
influence of coffee drinking on smoking, if any, can be attributed to the effects of caffeine.
Lane, J. D. (1994). "Neuroendocrine responses to caffeine in the work environment." Psychosomatic Medicine 56(3): 267-70.The effect of caffeine on neuroendocrine stress responses in the workplace was studied in 14 habitual coffee drinkers. Urinary catecholamine and cortisol levels were measured on 2 study days, in a 4-hour interval from morning until noon, while participants performed their normal work-related activities. Caffeine (300 mg) or placebo was administered blind at the beginning of study intervals, after overnight caffeine abstinence. Retrospective mood and symptom ratings were collected at the end of each morning. Caffeine elevated urinary epinephrine levels during work by 37% but did not affect norepinephrine or cortisol levels. Subjective reports suggest that caffeine abstinence was associated with symptoms of caffeine withdrawal by the end of the morning. Effects included higher ratings of sleepiness, lethargy, and headache and a reduced desire to socialize. Results suggest caffeine may increase the activity of the sympathetic adrenal-medullary system during everyday activities in the work environment. This action may potentiate psychophysiological responses elicited by occupational stressors.
Lane, J. D., Pieper, C. F., Barefoot, J. C., Williams, R. B., Jr. and Siegler, I. C. (1994). "Caffeine and cholesterol: interactions with hostility." Psychosomatic Medicine 56(3): 260-6.The consumption of caffeinated beverages has been linked to elevated serum cholesterol and an increased risk of coronary disease, although the relationships are inconsistent across studies and remain controversial. The effect of caffeine on cholesterol and coronary disease risk may be modulated by other factors. Using cohort data from a subsample of the University of North Carolina Alumni Heart Study, we investigated whether the relationships between caffeinated beverage consumption and serum lipid and lipoprotein levels in middle-aged men and women were modulated by levels of trait hostility. After adjustment for other risk factors, higher caffeinated beverage intake was associated with higher low-density lipoprotein cholesterol levels and a higher ratio of total to high-density lipoprotein cholesterol, both indicative of greater coronary disease risk. The interactive effects of hostility and caffeine intake were ambiguous, although there were trends for caffeine intake to have stronger effects on low-density lipoprotein and on total cholesterol in people with less hostility. Additional studies of personality characteristics and other factors that can modulate the cholesterol-raising effects of coffee drinking may be warranted because they might clarify the health consequences associated with coffee drinking and lead to the identification of individuals who would benefit most from changes in their coffee drinking.
Lane, J. D., Steege, J. F., Rupp, S. L. and Kuhn, C. M. (1992). "Menstrual cycle effects on caffeine elimination in the human female." European Journal of Clinical Pharmacology 43(5): 543-6.Increases in the levels of sex steroids due to pregnancy or oral contraceptive steroid use are known to decrease significantly the rate at which caffeine is eliminated from the body. An investigation has now been made into whether the changes in sex steroid levels that occur during normal menstrual cycling also affect the rate of caffeine elimination, especially whether hormonal shifts in the luteal phase are associated with slower elimination of caffeine. Repeated 24-hour caffeine elimination studies were conducted during the follicular and luteal phases of the menstrual cycle in 10 healthy women. Comparisons of the follicular and luteal phases revealed that systemic clearance of caffeine was slower in the luteal phase, although the t1/2 did not differ. The slowing effect was related to the proximity to onset of menstruation and to levels of progesterone. The evidence suggests that caffeine elimination may be slowed in the late luteal phase, prior to the onset of menstruation. Such a reduction would lead to increased accumulation of caffeine with repeated self-administration during the day, but the effect may be too small to be of clinical significance in the majority of women.
Lane, J. D., Adcock, R. A., Williams, R. B. and Kuhn, C. M. (1990). "Caffeine effects on cardiovascular and neuroendocrine responses to acute psychosocial stress and their relationship to level of habitual caffeine consumption." Psychosomatic Medicine 52(3): 320-36.The effects of a moderate dose of caffeine on cardiovascular and neuroendocrine stress reactivity were examined in 25 healthy male subjects selected as habitual or light consumers of caffeine. Measurements were taken under resting conditions before and after administration of caffeine (3.5 mg/kg) or placebo, during a stressful laboratory task, and in a post-stress recovery period. Caffeine elevated blood pressure and plasma norepinephrine levels at rest, effects which added significantly to the effects of stress. Caffeine potentiated stress-related increases in plasma epinephrine and cortisol stress, more than doubling the responses observed in the control condition. These effects were present in both habitual and light consumers and level of habitual caffeine consumption did not affect their magnitude. Results indicate that caffeine can potentiate both cardiovascular and neuroendocrine stress reactivity and that the habitual use of caffeine is not necessarily associated with the development of tolerance to these effects.
Lane, J. D. and Manus, D. C. (1989). "Persistent cardiovascular effects with repeated caffeine administration." Psychosomatic Medicine 51(4): 373-80.Although habitual caffeine users ingest the drug repeatedly throughout each day, the persistence of caffeine's known cardiovascular effects with such repeated use has not been investigated. Blood pressure and heart rate were measured under resting conditions in 10 healthy, male coffee or tea drinkers for 2 hours following a pretreatment dose of caffeine (125 mg) on two separate days after overnight abstinence. Either a second caffeine dose or placebo was administered and measurements continued for 1.5 hours. Compared to placebo, the second dose of caffeine produced significant increases in heart rate and diastolic and mean arterial, but not systolic, blood pressures. The results suggest that the cardiovascular effects of caffeine may persist throughout the day with repeated administration of moderate amounts of caffeine. Habitual caffeine use does not necessarily lead to complete tolerance, which suggests that caffeine's cardiovascular effects could contribute to an increased risk of cardiovascular disease.
Lane, J. D. and Williams, R. B., Jr. (1987). "Cardiovascular effects of caffeine and stress in regular coffee drinkers." Psychophysiology 24(2): 157-64.Investigated the effects of caffeine on cardiovascular activity at rest and in response to psychological stress in 30 healthy male coffee drinkers (aged 19-28 yrs) to replicate caffeine^stress interactions found by the present authors (see PA, Vol 74:3435) in caffeine-naive Ss. Relative to placebo, caffeine (250 mg) had a pressor effect at rest that persisted during stress and recovery. Caffeine magnified forearm blood flow and vascular resistance responses to stress, suggesting a synergistic interaction with stress. Forearm vascular effects were greatest in Type B (noncoronary-prone) Ss with a family history of hypertension. Results suggest that regular caffeine use does not necessarily lead to tolerance for caffeine/stress interactions.
Lane, J. D. and Williams, R. B., Jr. (1985). "Caffeine affects cardiovascular responses to stress." Psychophysiology 22(6): 648-55.The effects of caffeine on cardiovascular activity at rest and during psychological stress were examined in 33 healthy male undergraduates who did not normally ingest caffeinated products. Caffeine (250 mg) and placebo were administered double-blind in separate sessions. Heart rate, blood pressure, and forearm blood flow and vascular resistance were assessed at rest and during the stressful, competitive performance of a mental arithmetic task. Comparisons of caffeine and placebo sessions revealed that caffeine elevated resting blood pressure 4-6 mmHg, an effect added to the elevation produced by stress. Caffeine did not affect resting forearm blood flow but potentiated the forearm blood flow response to stress and led to higher levels of flow during stress. No caffeine effects appeared in heart rate or in task performance. Family history of hypertension and Type A behavior were examined as potential modulating factors of caffeine effects, but results were generally negative. It is concluded that these results suggest possible mechanisms through which caffeine could enhance the pathogenic effects of stress on the cardiovascular system.
Lane, J. D. (1983). "Caffeine and cardiovascular responses to stress." Psychosomatic Medicine 45(5): 447-51.Caffeine and psychologic stress have similar physiologic effects. Moderate doses of caffeine were found to elevate blood pressure in healthy, young males during periods of rest and stress. Blood pressure during stress was also significantly higher after caffeine had been consumed. The elevation of blood pressure due to caffeine appears to add to that elicited by stress. The implications of these results for prevention and treatment of cardiovascular disease are discussed.
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