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Caffeine, postmenopausal
estrogen, and risk of Parkinson's disease. |
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Effects of caffeine on human
health. |
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Effects of coffee and caffeine
on fertility, reproduction, lactation, and development. Review
of human and animal data. |
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Caffeine: an update. |
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Coffee, tea, and caffeine
consumption and breast cancer incidence in a cohort of Swedish
women. |
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Effects of caffeine on bone
and the calcium economy. |
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Caffeine and coffee: effects
on health and cardiovascular disease. |
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Caffeine intake and low birth
weight: a population-based case-control study. |
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Selected health and behavioral
effects related to the use of caffeine. |
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Regular caffeine consumption:
a balance of adverse and beneficial effects for mood and psychomotor
performance. |
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Caffeine affects cardiovascular
and neuroendocrine activation at work and home. |
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Effect of coffee consumption
on intraocular pressure. |
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Coffee intake and risk of
hypertension: the Johns Hopkins precursors study. |
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Coffee, caffeine and blood
pressure: a critical review. |
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The effect of caffeine on
ambulatory blood pressure in hypertensive patients. |
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A prospective study of coffee
drinking and suicide in women. |
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Coffee consumption and risk
of ischaemic heart disease - a settled issue? |
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Coffee intake and coronary
heart disease. |
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Coffee consumption and cause-specific
mortality. Association with age at death and compression of
mortality. |
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Cardiovascular effects of
coffee consumption in the aged: the CASTEL epidemiologic study. |
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Mortality patterns among
hypertensives by reported level of caffeine consumption. |
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Coffee consumption and blood
pressure: an Italian study. |
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Coffee consumption and the
incidence of coronary heart disease. |
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Coffee and health. |
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Coffee consumption and the
risk of coronary heart disease and death. |
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Coffee and tea consumption
in the Scottish Heart Health Study follow up: conflicting relations
with coronary risk factors, coronary disease, and all cause
mortality. |
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Coffee consumption and coronary
heart disease in women. A ten-year follow-up. |
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Coffee
contains a complex mixture of chemical compounds. Some components,
particularly those related to the aroma, are produced during roasting
of the green beans. The substances which during "brewing"
dissolve in water to form the beverage are classified as nonvolatile
taste components (including caffeine, trigonelline, chlorogenic
acid, phenolic acids, amino acids, carbohydrates, and minerals)
and volatile aroma components including organic acids, aldehydes,
ketones, esters, amines, and mercaptans.
The major physiologically active substance in
coffee is the alkaloid caffeine (C_8 H_10 O_2 N_4·H_2 O),
also called guaranine or methyltheobromine, which acts as a mild
stimulant. Caffeine is a naturally occurring substance found in
the leaves, seeds or fruits of more than 60 plants, including
coffee and cocoa beans, cola nuts and tea leaves. These are used
to make beverages such as coffee, tea and cola drinks, and foods
such as chocolate. Caffeine is also contained in many over-the-counter
(OTC) and prescription medications. In the United States, most
of the population uses caffeine in some form.
A cup of coffee, depending on the strength, may
contain some 20-100mg of caffeine. Some types of coffee may also
contain significant amounts of the B-vitamin niacin, although
this nutrient is of course readily available from other foods
as well. Caffeine-containing tablets or medications should not
be taken as well as cups of coffee or tea, since this would increase
the true dosage. The effects of caffeine vary from person to person;
some individuals can drink several cups of coffee in an hour and
notice no effects, while others may feel a strong effect after
just one serving. Caffeine is prohibited for competition athletes.
People who wish to avoid or minimise caffeine intake (see below)
often use decaffeinated coffee, or coffee substitutes. One method
of decaffeination is by treating the green beans (before roasting)
with chlorinated hydrocarbon solvents; other methods are also
used. Important coffee substitutes are chicory, and roasted cereals
such as barley; although these are commonly used not as total
substitutes but as "extenders". Under U.S. law, the
addition of chicory or any other substance must be clearly stated
on the label.
Caffeine is a drug that has been widely used
for centuries. Its main
effect is that it is a mild stimulant of the central nervous system
(CNS), helping to reduce feelings of drowsiness and fatigue. However,
regular use may lead to "habituation"; that is, no net
benefit from use but, rather, a negative effect if the drug is
not taken.
Besides the above-mentioned CNS stimulant effect,
caffeine also temporarily increases heartbeat, increases the blood
pressure, and stimulates the action of the lungs; increases basal
metabolic rate (BMR), and promotes urine production; and it relaxes
smooth muscles, notably the bronchial muscle. Caffeine is used
in treating migraine, either alone or in combination. It enhances
the action of the ergot alkaloids used for the treatment of this
problem, and also increases the potency of analgesics such as
aspirin. It can somewhat relieve asthma attacks by dilating the
bronchial airways.
Too much caffeine can produce restlessness, nausea,
headache, tense muscles, sleep disturbances, and cardiac arrhythmias
(irregular heartbeats). Because caffeine increases the production
of stomach acid it may worsen ulcer symptoms or cause acid reflux
("heartburn"). Evening use of caffeine may disrupt sleep
and cause insomnia.
Caffeine should be used with caution by people
with heart disease and high blood pressure (hypertension), and
by those suffering from the eye disease glaucoma. Caffeine medications
should generally not be used in children. Many children are already
consuming significant amounts of caffeine in drinks and food.
In this connection, a nutritional concern is that children may
choose fizzy drinks in preference to milk, thus getting "empty"
calories at the expense of valuable nutrients.
As already mentioned, some potentially harmful
effects of coffee are recognized, particularly for people who
should take few or no stimulants. Beyond this however, scientific
studies of the effects of caffeine have in general failed to prove
negative effects, although some have produced contradictory conclusions.
An individual study may produce interesting results which may
suggest fruitful directions for further research, but usually
it is only when several independent studies confirm one another,
and any contradictory results can be accounted for, that one can
have reasonable confidence in the safety of a drug -- particularly
an " optional" one like coffee.
Although caffeine does not fall into the class
of "addictive" drugs, it may be habit-forming. Some
people may experience headache, fatigue, irritability and nervousness
when their daily intake of caffeine is quickly and substantially
altered.
Such "withdrawal effects" may be responsible
for confusing results in some studies. There are many complicating
factors in long-term studies. One is the familiar "convergence
of risk-factors" (e.g. that coffee-drinkers may be more likely
to be smokers). Another is that many of the study subjects may
deliberately change (or have previously changed) their consumption
habits or behaviour, e.g. in response to discovering that they
suffer from hypertension. There may also be significant differences
in methods of coffee preparation between study populations, or
over long periods of time.
Moderate caffeine consumption during pregnancy
is generally considered safe. A study has not found any effect
on low birth-weight or incidence of premature births. However,
although it has been suggested that caffeine may stimulate milk
production, cautious mothers may prefer to avoid such beverages
during pregnancy or while breastfeeding.
Furthermore, a large study has not shown any
connection of coffee or tea consumption with breast-cancer incidence.
Osteoporosis is another condition which particularly affects women.
Previous studies have suggested caffeine consumption as a risk-factor,
but a recent analysis concludes that such an effect is probably
not significant except in conditions of calcium-deficiency, which
can be easily corrected.
There is even some actual positive news. The
effect of caffeine on the risk of developing Parkinson's disease,
which usually affects older people, has been found to be favourable
for men. For women, previous results have been confusing; but
a recent study suggests that a crucial factor may be the effect
of hormone levels. Often caffeine may have a favourable effect
against developing this disease; but when combined with hormone
replacement therapy (HRT), it may have a negative one.
One study has found (for women) a strong
inverse association between coffee intake and risk of suicide.
However, even if confirmed, to determine whether this might be
actual cause and effect is, as usual, a much more challenging
problem.
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Departments of Nutrition (Drs. Ascherio
and Chen), Epidemiology (Drs. Ascherio, Zhang, and Colditz),
and Environmental Health (Dr. Speizer), Harvard School of
Public Health.
BACKGROUND: Men who regularly consume
caffeinated drinks have a lower risk of PD than do nondrinkers,
but this relation has not been found in women. Because this
sex difference could be due to hormonal effects, the authors
examined prospectively the risk of PD according to use of
postmenopausal hormones and caffeine intake among participants
in the Nurses' Health Study. METHODS: The study population
comprised 77,713 women free of PD, stroke, or cancer at baseline,
who were postmenopausal at baseline or reached menopause before
the end of the study. During 18 years of follow-up the authors
documented 154 cases of PD. RESULTS: Overall, the risk of
PD was similar in women using hormones and women who never
used hormones (relative risk 1.02, 95% CI 0.69 to 1.52). Use
of hormones, however, was associated with a reduced risk of
PD among women with low caffeine consumption (RR 0.39, 95%
CI 0.13 to 1.17), and with increased risk among women with
high caffeine consumption (RR 2.44, 95% CI 0.75 to 7.86; p
for interaction = 0.01). Among hormone users, women consuming
six or more cups of coffee per day had a fourfold higher risk
of PD (RR 3.92, 95% CI 1.49 to 10.34; p = 0.006) than did
women who never drink coffee. CONCLUSION: These results suggest
that caffeine reduces the risk of PD among women who do not
use postmenopausal hormones, but increases risk among hormone
users. Clinical trials of caffeine or estrogens in women should
avoid the combined use of these agents.
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Toxicological Evaluation Section, Chemical
Health Hazard Assessment Division, Bureau of Chemical Safety,
Food Directorate, Health Canada, Tunney's Pasture, PL 2204D1,
Ottawa, Ontario, Canada K1A 0L2. peter_nawrot@hc-sc.gc.ca
Caffeine is probably the most frequently
ingested pharmacologically active substance in the world.
It is found in common beverages (coffee, tea, soft drinks),
in products containing cocoa or chocolate, and in medications.
Because of its wide consumption at different levels by most
segments of the population, the public and the scientific
community have expressed interest in the potential for caffeine
to produce adverse effects on human health. The possibility
that caffeine ingestion adversely affects human health was
investigated based on reviews of (primarily) published human
studies obtained through a comprehensive literature search.
Based on the data reviewed, it is concluded that for the healthy
adult population, moderate daily caffeine intake at a dose
level up to 400 mg day(-1) (equivalent to 6 mg kg(-1) body
weight day(-1) in a 65-kg person) is not associated with adverse
effects such as general toxicity, cardiovascular effects,
effects on bone status and calcium balance (with consumption
of adequate calcium), changes in adult behaviour, increased
incidence of cancer and effects on male fertility. The data
also show that reproductive-aged women and children are 'at
risk' subgroups who may require specific advice on moderating
their caffeine intake. Based on available evidence, it is
suggested that reproductive-aged women should consume
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INSERM U 272, Universite de Nancy I.
In the present review, we have examined
the effects of coffee ingestion on fertility, reproduction,
lactation and development. The potential effects of coffee
consumption on fertility, spontaneous abortion and prematurity
are not clearly established but appear to be quite limited.
In rodents, caffeine can induce malformations but this effect
appears in general at doses never encountered in humans. Indeed,
as soon as the quantity of caffeine is divided over the day,
as is the case for human consumption, the teratogenic effect
of caffeine disappears in rodents. Coffee ingested during
gestation induces a dose-dependent decrease in birth weight,
but usually only when ingested amounts are high (i.e. more
than 7 cups/day), whereas coffee has no effect at moderate
doses. Caffeine consumption during gestation affects hematologic
parameters of the new-born infant or rat. In animals, caffeine
induces long-term consequences on sleep, locomotion, learning
abilities, emotivity and anxiety, whereas, in children, the
effects of early exposure to coffee and caffeine on behavior
are not clearly established. The quantities of caffeine found
in maternal milk vary with authors, but it appears clearly
that caffeine does not change maternal milk composition and
has a tendency to stimule milk production. In conclusion to
this review, it appears that maternal coffee or caffeine consumption
during gestation and/or lactation does not seem to have measurable
consequences on the fetus of the newborn, as long as ingested
quantities remain moderate. Therefore, pregnant mothers should
be advised to limit their coffee and caffeine intake to 300
mg caffeine/day (i.e. 2-3 cups of coffee or 2.5-3 l of coke)
especially because of the increase of caffeine half-life during
the third trimester of pregnancy and in the neonate.
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While the total annual volume of caffeine
has increased over the years, the actual per capita daily
intake has not. This is based on the fact that the quantity
of caffeine in a soft drink is about the same or, in the case
of diet drinks, less than in 1961 when the original GRAS (Generally
Recognized as Safe) determinations were made. Since that time,
there have been numerous studies on the effect of caffeine
on animals and humans. The Select Committee on GRAS Substances
(SCOGS) of the Federation of American Societies for Experimental
Biology (FASEB) in 1978 reviewed all the data available at
that time and concluded that there is "no evidence in the
available information on caffeine [that] demonstrates a hazard
to the public when it is used in cola-type beverages at levels
that are now current and in the manner now practiced...",
although they did suggest further study was necessary. The
Flavor and Extract Manufacturers' Association (FEMA) Expert
Panel has now reviewed not only the same data s the FASEB
(SCOGS) Committee, but several more recent studies. On the
basis of this review, the Panel reaffirms the GRAS status
of caffeine under conditions of its current use as an international
ingredient in nonalcoholic beverages.
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Obstetrics & Gynecology Epidemiology
Center, Brigham & Women's Hospital, Harvard Medical School,
Boston, MA 02115, USA.
PURPOSE: Coffee, caffeinated tea, and
caffeine have been suggested to play a role in breast carcinogenesis
or in the promotion or inhibition of tumor growth. Prior epidemiologic
evidence has not supported an overall association between
consumption of caffeinated beverages and risk of breast cancer,
but consumption in some studies was low. METHODS: We studied
this relation in the Swedish Mammography Screening Cohort,
a large population-based prospective cohort study in Sweden
comprising 59,036 women aged 40-76 years. Sweden has the highest
coffee consumption per capita in the world. RESULTS: During
508,267 person-years of follow-up, 1271 cases of invasive
breast cancer were diagnosed. Women who reported drinking
4 or more cups of coffee per day had a covariate-adjusted
hazard ratio of breast cancer of 0.94 [95% confidence interval
(CI) 0.75-1.28] compared to women who reported drinking 1
cup a week or less. The corresponding hazard ratio for tea
consumption was 1.13 (95% CI 0.91-1.40). Similarly, women
in the highest quintile of self-reported caffeine intake had
a hazard ratio of beast cancer of 1.04 (95% CI 0.87-1.24)
compared to women in the lowest quintile. CONCLUSIONS: In
this large cohort of Swedish women, consumption of coffee,
tea, and caffeine was not associated with breast cancer incidence.
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Creighton University, 2500 California
Plaza, Omaha, Nebraska 68178, USA. rheaney@creighton.edu
Caffeine-containing beverage consumption
has been reported to be associated with reduced bone mass
and increased fracture risk in some, but not most, observational
studies. Human physiological studies and controlled balance
studies show a clear but only a very small depressant effect
of caffeine itself on intestinal calcium absorption, and no
effect on total 24-h urinary calcium excretion. The epidemiologic
studies showing a negative effect may be explained in part
by an inverse relationship between consumption of milk and
caffeine-containing beverages. Low calcium intake is clearly
linked to skeletal fragility, and it is likely that a high
caffeine intake is often a marker for a low calcium intake.
The negative effect of caffeine on calcium absorption is small
enough to be fully offset by as little as 1-2 tablespoons
of milk. All of the observations implicating caffeine-containing
beverages as a risk factor for osteoporosis have been made
in populations consuming substantially less than optimal calcium
intakes. There is no evidence that caffeine has any harmful
effect on bone status or on the calcium economy in individuals
who ingest the currently recommended daily allowances of calcium.
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Cardiology Division, Moffitt-Long Hospitals,
University of California, San Francisco 94143-1220.
Caffeine is a methylxanthine whose primary
biological effect is the competitive antagonism of the adenosine
receptor. Its presence in coffee, tea, soda beverages, chocolate
and many prescription and over-the-counter drugs makes it
a commonly consumed stimulant. Coffee and/or caffeine consumption
has been linked to many human diseases in epidemiologic studies.
Causal relationships have been difficult to substantiate.
Initial investigations, showing an association between coffee
and coronary heart disease, suffer from confounding variables
and have been difficult to replicate. Recent studies, showing
a significant effect over long follow-up periods and with
high coffee intake, have again raised the question of a role
for coffee and/or caffeine consumption in the pathogenesis
of atherosclerotic heart disease. Contrary to common belief,
the published literature provides little evidence that coffee
and/or caffeine in typical dosages increases the risk of infarction,
sudden death or arrhythmia.
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Pos-Graduacao em Epidemiologia, Universidade
Federal de Pelotas, Brazil.
The authors conducted a matched case-control
study to investigate the effects of caffeine intake during
pregnancy on birth weight. From January to November 1992,
in the first 24 hours after delivery, 1,205 mothers (401 cases
and 804 controls) were interviewed and their newborns were
examined to assess birth weight and gestational age by means
of the method of Capurro et al. (J Pediatr 1978;93:120-2).
The cases were children with birth weight < 2,500 g and gestational
age > or = 28 weeks. Cases and controls were matched for time
of birth and hospital of delivery and were recruited from
the four maternity hospitals in Pelotas, southern Brazil.
Daily maternal caffeine intake during pregnancy for each trimester
was estimated. To assess caffeine intake, 10% of the mothers
were reinterviewed at their households and samples of reported
information on drip coffee and mate (a caffeine-containing
drink widely used in South America) were collected and sent
to the laboratory for caffeine determination through liquid
chromatography. When instant coffee was reported, the weight
of powder was measured using a portable scale, and caffeine
intake was estimated from a reference table. Caffeine intake
from tea, chocolate, soft drinks, and medicines was estimated
from a reference table. Analyses were performed by conditional
logistic regression. Crude analyses showed no effect of caffeine
on low birth weight, preterm births or intrauterine growth
retardation. The results did not change after allowing for
confounders.
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Department of Health and Community Services,
California State University, Chico 95929-0505.
This paper reviews the research literature
concerning health and selected behavioral effects of caffeine.
Epidemiological and laboratory findings are reviewed to determine
the health risks associated with both acute and chronic caffeine
exposure. Common sources of caffeine, its properties, and
physiological effects are considered. The relationships between
caffeine and various health conditions are examined including
caffeine's association with heart disease, cancer, and benign
breast disease. Caffeine's possible contribution to enhanced
exercise performance is discussed along with a brief overview
of caffeine's effects on mental and emotional health. Over
100 references cited in this review were part of a more extensive
literature base obtained from several on-line services including
MEDLINE and LEXIS/NEXIS medical data bases. Other sources
of relevant literature included manual searches of research
journals and the use of selected references from appropriate
articles. The relationship between caffeine consumption and
various illnesses such as cardiovascular disease and cancer
remains equivocal. Prudence might dictate that pregnant women
and chronically ill individuals exercise restraint in their
use of caffeine, although research suggests relatively low
or nonexistent levels of risk associated with moderate caffeine
consumption.
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Consumer Sciences Department, Institute
of Food Research, Reading Laboratory, UK.
It has often been pointed out that caffeine
is the most widely "used" psychoactive substance in the world,
and accordingly, there is a very large amount of research
available on the effects of caffeine on body and mind. In
particular, a psychostimulant action of caffeine is generally
accepted as well established; for example, caffeine has been
found to quicken reaction time and enhance vigilance performance,
and to increase self-rated alertness and improve mood. There
is, however, a real difficulty in determining the net effects
of caffeine. In a typical experiment the subjects have a history
of regular caffeine consumption, and they are tested on caffeine
and a placebo after a period of caffeine deprivation (often
overnight). The problem with relying solely on this approach
is that it leaves open the question as to whether the results
obtained are due to beneficial effects of caffeine or to deleterious
effects of caffeine deprivation. The present article briefly
reviews this evidence on the psychostimulant effects of caffeine,
and presents some new data testing the hypothesis that caffeine
may enhance cognitive performance to a greater extent in older
adults than in young adults. No age-related differences in
the effects of caffeine on psychomotor performance were found.
We conclude that overall there is little unequivocal evidence
to show that regular caffeine use is likely to substantially
benefit mood or performance. Indeed, one of the significant
factors motivating caffeine consumption appears to be "withdrawal
relief."
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Department of Psychiatry and Behavioral
Sciences, Duke University Medical Center, Durham, NC 27710,
USA. jdlane@acpub.duke.edu
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.
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Department of Ophthalmology and External
Eye Disease Clinic, Rabin Medical Center, Petah Tiqva, Israel.
lavisar@bezeqint.net.
BACKGROUND: Many ophthalmologists instruct
patients with glaucoma to avoid coffee, although data supporting
this practice are insufficient. OBJECTIVE: To estimate the
effect of drinking coffee on intraocular pressure (IOP). METHODS:
In this crossover study, the effect of the consumption of
regular (180 mg caffeine in 200 mL beverage) and decaffeinated
coffee (3.6 mg caffeine in 200 mL beverage) was compared in
patients with normotensive glaucoma (n = 6) or ocular hypertension
(n = 22). IOP was monitored in both groups at 30, 60, and
90 minutes after coffee ingestion. RESULTS: In patients with
normotensive glaucoma who drank regular coffee, the mean +/-
SD changes in IOP at 30, 60, and 90 minutes were 0.9 +/- 0.5,
3.6 +/- 1.1, and 2.3 +/- 0.66 mm Hg, respectively; in those
who drank decaffeinated coffee, they were 0.75 +/- 0.36, 0.70
+/- 0.4, and 0.4 +/- 0.6 mm Hg, respectively. The corresponding
values in patients with ocular hypertension were as follows:
after regular coffee, 1.1 +/- 0.7, 3.4 +/- 1.0, and 3.0 +/-
2.7 mm Hg; and after decaffeinated coffee, 0.6 +/- 0.4, 0.9
+/- 0.2, and 0.5 +/- 0.5 mm Hg. The difference in the change
in IOP from baseline after ingestion of regular versus decaffeinated
coffee was statistically significant in each group at 60 and
90 minutes. Subjects who drank regular coffee demonstrated
a greater elevation in IOP; this elevation may be clinically
significant. CONCLUSIONS: Intake of caffeinated beverage (>/=180
mg caffeine) may not be recommended for patients with normotensive
glaucoma or ocular hypertension.
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The Johns Hopkins Precursors Study, 2024
E Monument St, Suite 2-200, Baltimore, MD 21205-2223, USA.
BACKGROUND: Whether the increase in
blood pressure with coffee drinking seen in clinical trials
persists over time and translates into an increased incidence
of hypertension is not known. METHODS: We assessed coffee
intake in a cohort of 1017 white male former medical students
(mean age, 26 years) in graduating classes from 1948 to 1964
up to 11 times over a median follow-up of 33 years. Blood
pressure and incidence of hypertension were determined annually
by self-report, demonstrated to be accurate in this cohort.
RESULTS: Consumption of 1 cup of coffee a day raised systolic
blood pressure by 0.19 mm Hg (95% confidence interval, 0.02-0.35)
and diastolic pressure by 0.27 mm Hg (95% confidence interval,
0.15-0.39) after adjustment for parental incidence of hypertension
and time-dependent body mass index, cigarette smoking, alcohol
drinking, and physical activity in analyses using generalized
estimating equations. Compared with nondrinkers at baseline,
coffee drinkers had a greater incidence of hypertension during
follow-up (18.8% vs. 28.3%; P =.03). Relative risk (95% confidence
interval) of hypertension associated with drinking 5 or more
cups a day was 1.35 (0.87-2.08) for baseline intake and 1.60
(1.06-2.40) for intake over follow-up. After adjustment for
the variables listed above, however, these associations were
not statistically significant. CONCLUSION: Over many years
of follow-up, coffee drinking is associated with small increases
in blood pressure, but appears to play a small role in the
development of hypertension.
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Institute of Biomedicine, Department
of Pharmacology and Toxicology, University of Helsinki, Finland.
marja-leena.nurminen@helsinki.fi
OBJECTIVE: We review the published data
relating to intake of coffee and caffeine on blood pressure
in man. We also refer to studies on the possible mechanisms
of actions of these effects of caffeine. DESIGN: The MEDLINE
and Current Contents databases were searched from 1966 to
April 1999 using the text words 'coffee or caffeine' and 'blood
pressure or hypertension'. Controlled clinical and epidemiologic
studies on the blood pressure effects of coffee or caffeine
are reviewed. We also refer to studies on the possible mechanisms
of action of these effects of caffeine. RESULTS: Acute intake
of coffee and caffeine increases blood pressure. Caffeine
is probably the main active component in coffee. The pressor
response is strongest in hypertensive subjects. Some studies
with repeated administration of caffeine showed a persistent
pressor effect, whereas in others chronic caffeine ingestion
did not increase blood pressure. Epidemiologic studies have
produced contradictory findings regarding the association
between blood pressure and coffee consumption. During regular
use tolerance to the cardiovascular responses develops in
some people, and therefore no systematic elevation of blood
pressure in long-term and in population studies can be shown.
CONCLUSIONS: We conclude that regular coffee may be harmful
to some hypertension-prone subjects. The hemodynamic effects
of chronic coffee and caffeine consumption have not been sufficiently
studied. The possible mechanisms of the cardiovascular effects
of caffeine include the blocking of adenosine receptors and
the inhibition of phosphodiesterases.
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Chorley Hypertension Institute, Chaim
Sheba Medical Center, Tel Hashomer, Israel.
Because the potential impact of habitual
caffeine intake on blood pressure is a controversial issue,
a study was carried out to explore the relationship between
caffeine and various humoral factors that could account for
a coffee-induced rise in blood pressure. Twenty-three hypertensive
patients who refrained from caffeine for 2 to 3 weeks were
given 250 mg oral caffeine powder dissolved in water. Blood
pressure was recorded every 15 min by blood pressure monitor.
Caffeine blood level, renin and endothelin were measured before
and 1, 2, 3, and 6 h after caffeine intake. Urinary electrolytes
and catecholamines were measured under caffeine influence
(period I), and for the next 6 h (period II). A significant
increase in systolic (P = .017) and diastolic blood pressure
(P = .023) occurred in 13 subjects who were 58 +/- 10.4 years
old. Nonresponders were younger (44.5 +/- 15.8 years). A statistically
significant decrease in heart rate was seen during the first
hour after caffeine intake in both responders (P = .008) and
nonresponders (P = .004). Marked diuresis and natriuresis
were observed during period I in both groups. Renin and endothelin
levels were unchanged. Although chronic studies point to development
of tolerance to long-term caffeine ingestion, acute studies
like the one described are essential to obtain data on the
immediate effects that can be of practical importance, especially
in the elderly.
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Channing Laboratory, Department of Medicine,
Harvard Medical School, Boston, Mass., USA.
BACKGROUND: Among the many reported
central nervous system effects of long-term caffeine use is
improvement in mood. OBJECTIVE: To examine prospectively the
relationship of coffee and caffeine intake to risk of death
from suicide. METHODS: We conducted a 10-year follow-up study
(1980 to 1990) in an ongoing cohort of 86 626 US female registered
nurses aged 34 to 59 years in 1980, who were free of diagnosed
coronary heart disease, stroke, or cancer. Information on
coffee and caffeine intake was collected by a semiquantitative
food frequency questionnaire in 1980. Deaths from suicide
were determined by physician review of death certificates.
RESULTS: Fifty-six cases of suicide occurred during 832 704
person-years of observation. Compared with non-drinkers of
coffee, the age-adjusted relative risk of suicide in women
who consumed two to three cups per day was 0.34 (95% confidence
interval [CI, 0.17 to 0.68) and 0.42 (95% CI, 0.21 to 0.86)
in women who consumed four or more cups per day (P for linear
trend=.002). These findings remained essentially unchanged
after adjusting for a broad range of potential confounding
factors, including smoking habit, alcohol intake, medication
use (diazepam and phenothiazine), history of comorbid disease
(hypertension, hypercholesterolemia, or diabetes), marital
status, and self-reported stress. A strong inverse relationship
was similarly found for caffeine intake from all sources and
risk of suicide. CONCLUSIONS: The data suggest a strong inverse
association between coffee intake and risk of suicide. Whether
regular intake of coffee or caffeine has clinically significant
effects on the maintenance of affect or the prevention of
depression merits further investigation in clinical trials
and population-based prospective studies.
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Epidemiological Research Unit, Copenhagen
Male Study, Denmark.
OBJECTIVE. Based on a meta-analysis,
it was recently stated that there is no association between
coffee consumption and the risk of coronary heart disease.
Why then, have studies on the issue shown quite variable results?
DESIGN SETTING AND SUBJECTS. A prospective study was performed
in the Copenhagen Male Study on 2975 men (53-74 years) without
cardiovascular disease at baseline in 1985/1986. They were
classified according to self-reported consumption of filter
coffee. Some 147 men (5%) were coffee abstainers. Potential
confounders were alcohol use, physical activity, smoking,
serum cotinine, serum lipids, serum selenium, body mass index,
blood pressure, Lewis blood group, hypertension, non-insulin-dependent
diabetes mellitus and social class. MAIN OUTCOME MEASURES.
The incidence of ischaemic heart disease (IHD) 1985/86-1991.
RESULTS. Some 184 men had a first IHD event. There was no
significant difference between those consuming 1-4, 5-8 or
> or = 9 cups per day after controlling for confounders (P-value
of trend test: 0.14). The crude incidence rates were 6.8,
6.7 and 4.6%, respectively; the adjusted rates were 6.8, 6.7
and 4.0%, respectively. Coffee consumption was significantly
(P < 0.05) inversely correlated with serum selenium concentration
(never previously described) and, positively or negatively,
with a number of other potential risk factors: smoking, alcohol
use, serum triglycerides, serum cholesterol, blood pressure,
social class, body mass index, and serum selenium. In nonsmokers
and smokers of only a small amount of tobacco, coffee consumption
was associated with a lower risk of IHD (P < 0.05). CONCLUSION.
We conclude that the association between coffee consumption
and risk of IHD is conditioned by known risk factors correlated
with use of coffee, which may partly explain the inconsistencies
in the results of previous studies.
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Department of Medicine, Johns Hopkins
University School of Medicine, Baltimore.
We examined the risk of coronary heart
disease (CHD) associated with coffee intake in 1040 male medical
students followed for 28 to 44 years. During the follow-up,
CHD developed in 111 men. The relative risks (95% confidence
interval) associated with drinking 5 cups of coffee/d were
2.94 (1.27, 6.81) for baseline, 5.52 (1.31, 23.18) for average,
and 1.95 (0.86, 4.40) for most recent intake after adjustment
for baseline age, serum cholesterol levels, calendar time,
and the time-dependent covariates number of cigarettes, body
mass index, and incident hypertension and diabetes. Risks
were elevated in both smokers and nonsmokers and were stronger
for myocardial infarction. Most of the excess risk was associated
with coffee drinking prior to 1975. The diagnosis of hypertension
was associated with a subsequent reduction in coffee intake.
Negative results in some studies may be due to the assessment
of coffee intake later in life or to differences in methods
of coffee preparation between study populations or over calendar
time.
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Loma Linda University, CA 92354.
The relationship between reported coffee
consumption and specific causes of death was examined in 9484
males enrolled in the Adventist Mortality Study in 1960 and
followed through 1985. Coffee consumption was divided into
three levels: less than 1 cup per day, 1-2 cups per day, and
greater than or equal to 3 cups per day. Approximately one
third of the subjects did not drink coffee. Cause-specific
mortality rates were compared using survival analysis including
Cox's proportional hazard model, and controlling for potential
confounders such as body mass index, heart disease and hypertension
at baseline, race, physical activity, marital status, educational
level, smoking history, and dietary pattern. Inclusion of
interaction terms between coffee consumption and attained
age as time-dependent covariates allowed the hazard ratio
to vary with age. Univariate analyses showed a statistically
significant association (p less than 0.05) for coffee consumption
and mortality for most endpoints. Multivariate analyses showed
a small but statistically significant association between
coffee consumption and mortality from ischemic heart disease,
other cardiovascular diseases, all cardiovascular diseases,
and all causes of death. For the major causes of death, the
hazard ratios decreased from about 2.5 at 30 years of age
to 1.0 around 95 years of age. These results indicate that
abstinence from coffee leads to compression of mortality rather
than an increase in lifespan.
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Clinica Medica I, Universita degli Studi,
Padova.
The data obtained from 2240 subjects
aged 65 years or more from the general population of Castelfranco
Veneto (Italy) included in the CASTEL (CArdiovascular STudy
in the ELderly) epidemiological Italian project were analyzed
in relation to coffee consumption. Subjects were divided into
3 classes: class 1 (N = 109): non coffee drinkers; class 2
(N = 1554): 1 to 2 cups of coffee per day; class 3 (N = 577):
3 or more cups per day. The results were described by ANOVA,
Tukey post hoc test and Pearson correlation coefficient with
Bonferroni's conservative correction. In classes 2 and 3 total
cholesterol, apolipoprotein B100 and calculated LDL-cholesterol
were higher than in class 1. The number of cups of coffee
per day directly correlated to both the number of cigarettes
per day and the number of drinks per week. Although these
data seem to indicate a convergence of risk factors (cholesterol,
smoking, alcohol) in coffee drinkers, no increase in the prevalence
of cardiovascular events was found in coffee drinkers in comparison
with non drinkers. This could be attributed to the fact that
prevalence of hypertension and diabetes did not increase with
increasing coffee consumption; on the contrary, they were
lower in classes 2 and 3 than in class 1.
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School of Allied Health Sciences, Program
in Nutrition and Dietetics, University of Texas Health Science
Center 77225.
The effect of caffeine consumption on
mortality was evaluated in a historical cohort study of 10,064
diagnosed hypertensive individuals participating in the Hypertension
Detection and Follow-up Program from 1973 to 1979. Total caffeine
intake level from beverages (coffee and tea) and certain medications,
was estimated at the 1-year visit. No evidence was found supporting
an association between increased level of caffeine consumption
and increased all-cause mortality or cardiovascular disease
mortality during the following 4 years. Cigarette smoking
was significantly associated with mortality; the association
being more pronounced among non- and low-caffeine consumers
for all-cause mortality and among non-caffeine consumers for
all cardiovascular mortality except cerebrovascular mortality.
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The relation between habitual coffee
consumption and blood pressure was studied in 500 Italian
subjects, males and females, aged 18-62 years. After allowing
for sex, age and weight, the pressure levels showed a significant
decrease with increasing coffee consumption. Systolic blood
pressure (SBP) and diastolic blood pressure (DBP) were respectively
130.4 +/- 1.8 (SE) mmHg and 81.5 +/- 1.1 mmHg for non-coffee
drinkers, 129.4 +/- 1.4 and 82.2 +/- 0.9 mmHg for 1 cup per
day, 128.4 +/- 0.8 and 81.4 +/- 0.5 mmHg for 2-3 cups per
day, 124.9 +/- 1.1 and 78.8 +/- 0.7 mmHg for 4-6 cups per
day, and 124.1 +/- 2.5 and 78.7 +/- 1.6 mmHg for more than
6 cups of coffee daily (analysis of covariance: SBP F = 3.46,
4 df, P less than 0.01; DBP F = 3.46, 4 df, P less than 0.01).
Even after correcting pressure levels for habitual alcohol
intake and cigarette smoking, we observed a mean reduction
in SBP and DBP of 0.80 mmHg and 0.48 mmHg respectively per
cup per day.
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We conducted a prospective investigation
of the effect of coffee consumption on coronary heart disease
in 1130 male medical students who were followed for 19 to
35 years. Changes in coffee consumption and cigarette smoking
during follow-up were examined in relation to the incidence
of clinically evident coronary disease in comparisons of three
measures of coffee intake--base-line intake, average intake,
and most recent intake reported before the manifestation of
coronary disease. Clinical evidence of coronary disease included
myocardial infarction, angina, and sudden cardiac death. In
separate analyses for each measure of coffee intake, the relative
risks for men drinking five or more cups of coffee per day,
as compared with nondrinkers, were approximately 2.80 for
all three measures in the univariate analyses (maximum width
of 95 percent confidence intervals, 1.27 to 6.51). After adjustment
for age, current smoking, hypertension status, and base-line
level of serum cholesterol, the estimated relative risk for
men drinking five or more cups of coffee per day (using the
most recent coffee intake measure), as compared with those
drinking none, was 2.49 (maximum width of 95 percent confidence
interval, 1.08 to 5.77). The association between coffee and
coronary disease was strongest when the time between the reports
of coffee intake and the coronary event was shortest. These
findings support an independent, dose-responsive association
of coffee consumption with clinically evident coronary heart
disease, which is consistent with a twofold to threefold elevation
in risk among heavy coffee drinkers.
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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.
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Division of Nutrition, University of
Helsinki, PO Box 27, Latokartanonkaari 9, 00014 University
of Helsinki, Finland.
OBJECTIVES: To study prospectively the
relation of coffee drinking with fatal and nonfatal coronary
heart disease (CHD) and all-cause mortality and to perform
a cross-sectional analysis at baseline on the association
between coffee drinking and CHD risk factors, diagnosed diseases,
self-reported symptoms, and use of medicines. METHODS: The
study cohort consisted of 20 179 randomly selected eastern
Finnish men and women aged 30 to 59 years who participated
in a cross-sectional risk factor survey in 1972, 1977, or
1982. Habitual coffee drinking, health behavior, major known
CHD risk factors, and medical history were assessed at the
baseline examination. Each subject was followed up for 10
years after the survey using the national hospital discharge
and death registers. Multivariate analyses were performed
by using the Cox proportional hazards model. RESULTS: In men,
the risk of nonfatal myocardial infarction was not associated
with coffee drinking. The age-adjusted association of coffee
drinking was J shaped with CHD mortality and U shaped with
all-cause mortality. The highest CHD mortality was found among
those who did not drink coffee at all (multivariate adjusted).
Also, in women, all-cause mortality decreased by increasing
coffee drinking. The prevalence of smoking and the mean level
of serum cholesterol increased with increasing coffee drinking.
Non-coffee drinkers more often reported a history of various
diseases and symptoms, and they also more frequently used
several drugs compared with coffee drinkers. CONCLUSIONS:
Coffee drinking does not increase the risk of CHD or death.
In men, slightly increased mortality from CHD and all causes
in heavy coffee drinkers is largely explained by the effects
of smoking and a high serum cholesterol level.
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Department of Applied Statistics, University
of Reading.
STUDY OBJECTIVE: To relate habitual
(cups per day) tea and coffee consumption to conventional
coronary risk factors and subsequent risk of coronary heart
disease and death. DESIGN: Cohort study. SETTING: Nationwide
random population study. PARTICIPANTS: Over 11,000 men and
women aged 40-59 who took part in the Scottish Heart Health
Study lifestyle and risk factor survey in 1984-87. Participants
were followed up to the end of 1993, an average of 7.7 years,
for all cause mortality, coronary death, or any major coronary
event (death, non-fatal infarction or coronary artery surgery).
Cox's proportional hazards regression model was used to estimate
the hazard in consumers of tea and coffee relative to the
zero consumption group, both before and after correction for
other factors. MAIN RESULTS: Coffee and tea consumption showed
a strong inverse relation. For many conventional risk factors,
coffee showed a weak, but beneficial, gradient with increasing
consumption, whereas increasing tea consumption showed the
reverse. Increasing coffee consumption was associated with
beneficial effects for mortality and coronary morbidity, whereas
tea showed the opposite. Adjusting for age and social class
had some effect in reducing associations. Multiple adjustment
for other risk factors removed the associations for tea and
most of those for coffee although there was a residual benefit
of coffee consumption in avoiding heart disease among men.
CONCLUSIONS: The epidemiological differences shown in this
study occurred despite the pharmacological similarities between
tea and coffee. Either they differ more than is realised,
or they identify contrasting associated lifestyle and health
risks, for which this multiple adjustment was inadequate.
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Channing Laboratory, Boston, MA 02115,
USA.
OBJECTIVE--To assess the relationship
between coffee consumption and risk of coronary heart disease
(CHD) among women. DESIGN--Prospective cohort study with coffee
consumption measured in 1980, 1984, and 1986, and follow-up
through 1990. SETTING--Female registered nurses in the United
States. PARTICIPANTS--A total of 85,747 US women 34 to 59
years of age in 1980 and without history of CHD, stroke, or
cancer. MAIN OUTCOME MEASURE--Ten-year incidence of CHD (defined
as nonfatal myocardial infarction or fatal CHD). RESULTS--During
10 years of follow-up we documented 712 cases of CHD. After
adjustment for age, smoking, and other CHD risk factors, we
found no evidence for any positive association between coffee
consumption and risk of subsequent CHD. For women drinking
six or more cups of caffeine-containing coffee per day in
1980, the relative risk was 0.95 (95% confidence interval,
0.73 to 1.26) compared with women who did not consume this
beverage. Similarly, there was no association when the first
4 years of follow-up were excluded, when nonfatal and fatal
CHD end points were examined separately, or when we updated
coffee consumption in 1984 or 1986 and examined only CHD during
the next 2-year interval. Further, there was no association
with caffeine intake from all sources combined or with decaffeinated
coffee consumption. CONCLUSIONS--These data indicate that
coffee as consumed by US women is not an important cause of
CHD.
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