Newsgroup: it.sport.atletica
Titolo: caffeina e cuore (lungo)

Brutte notizie per i devoti della tazzulilla prima di un allenamento o di
una gara...
:-(
Vi allego il riassunto giornalistico di un articolo scientifico, in cui si
documenta come la caffeina riduca la capacita' del flusso coronarico di
adeguarsi alle maggiori richieste di sangue del muscolo cardiaco sotto
sforzo.
Inoltre si ricorda come la caffeina sia uno stimolatore solo del livello
psichico, non  di quello fisico (posto che siano dissociabili...).
I ricercatori precisano comunque:
- di non aver valutato la performance atletica ma solo il flusso coronarico
- che la cosa e' piu' che altro un elemento di rischio per chi abbia
(magari anche senza saperlo)qualche problema coronarico.
Io penso che a 50 anni ormai prossimi, magari provo a cambiare abitudine...
;-)
Results suggest that coffee may impair peak heart function 
BETHESDA, MD -- January 13, 2006 -- 
In healthy volunteers, the equivalent of two cups of coffee reduced the
body's ability to boost blood flow to the heart muscle in response to
exercise, and the effect was stronger when the participants were in a
chamber simulating high altitude, according to a new study in the Jan. 17,
2006, issue of the Journal of the American College of Cardiology. 
"Whenever we do a physical exercise, myocardial blood flow has to increase
in order to match the increased need of oxygen. We found that caffeine may
adversely affect this mechanism. It partly blunts the needed increase in
flow," said Philipp A. Kaufmann, MD, FACC, from the University Hospital
Zurich and Center for Integrative Human Physiology CIHP in Zurich,. 
The researchers, including lead author Mehdi Namdar, MD, FACC, studied 18
young, healthy people who were regular coffee drinkers. The participants
did not drink any coffee for 36 hours prior to the study testing. In one
part of the study, PET scans that showed blood flow in the hearts of 10
participants were performed before and immediately after they rode a
stationary exercise bicycle. In the second part of the study, the same
type of myocardial blood-flow measurements were done in 8 participants who
were in a chamber simulating the thin air at about 15,000 feet (4,500
meters) altitude. The high-altitude test was designed to mimic the way
coronary artery disease deprives the heart muscle of sufficient oxygen. In
both groups, the testing procedure was repeated 50 minutes after each
participant swallowed a tablet containing 200 milligrams of caffeine, the
equivalent of two cups of coffee. The caffeine dose did not affect blood
flow within the heart muscle while the participants were at rest. However,
the blood flow measurements taken immediately after exercise were
significantly lower after the participants had taken caffeine tablets. The
effect was pronounced in the group in the high-altitude chamber. Blood
flow normally increases in response to exercise, and the results indicate
that caffeine reduces the body's ability to boost blood flow to the muscle
of the heart on demand. The ratio of exercise blood flow to resting blood
flow, called the myocardial flow reserve, was 22% lower in the group at
normal air pressure after ingesting caffeine and 39% lower in the group in
the high-altitude chamber. 
Dr. Kaufmann said that caffeine may block certain receptors in the walls
of blood vessels, interfering with the normal process by which adenosine
signals blood vessels to dilate in response to the demands of physical
activity. "Although these findings seem not to have a clinical importance
in healthy volunteers, they may raise safety questions in patients with
reduced coronary flow reserve, as seen in coronary artery disease,
particularly before physical exercise and at high-altitude exposure," the
researchers wrote. 
Although caffeine is a stimulant, these results also indicate that coffee
may not necessarily boost athletic performance. "We now have good evidence
that, at the level of myocardial blood flow, caffeine is not a useful
stimulant. It may be a stimulant at the cerebral level in terms of being
more awake and alert, which may subjectively give the feeling of having
better physical performance. But I now would not recommend that any
athlete drink caffeine before sports. It may not be a physical stimulant,
and may even adversely affect physical performance," Dr. Kaufmann said.
"It may not be as harmless as we thought before, particularly if you
suffer from coronary artery disease or if you are in the mountains." Dr.
Kaufmann noted that this study was not designed to measure athletic
performance. Although the participants were all healthy, Dr. Kaufmann said
that the results raise concerns about possible effects of caffeine in
people with heart disease. "Any advice would be based on results of
healthy volunteers and would be a bit speculative; nevertheless, my advice
would be: do not drink coffee before doing physical activities. We hope to
be able to provide data soon on the situation of patients with coronary
artery disease," he said. 
The researchers noted that other studies of coffee and heart disease have
produced mixed results. Although this study included only 18 participants,
the researchers said that the differences they saw were large enough for
them to be confident that the effect of caffeine on heart muscle blood
flow is real. They pointed out that longer studies of people with heart
disease will be needed in order to understand whether the blood flow
effects have important health consequences. 
Thomas H. Schindler, MD from the David Geffen School of Medicine at UCLA
in Los Angeles, California, who was not connected with this study, said
that if the results are confirmed, they could have important implications.
"In particular, this may play an important role in patients with
obstructive coronary artery disease in the intermediate range between 50%
and 85% narrowing of the epicardial luminal diameter. In this range of
coronary artery disease-induced epicardial narrowing, the myocardial flow
reserve (MFR) has been widely assumed to compensate for the epicardial
narrowing and, thereby, to preserve the myocardial blood flow to the
heart. A further reduction of the MFR, for example owing to caffeine
intake, therefore could precipitate stress-induced myocardial ischemia,
angina pectoris (reflecting an imbalance between myocardial oxygen supply
and demand) or could also contribute to the manifestation of acute
coronary syndromes. Consequently, as stated by Namdar et al., the current
findings indeed raise safety questions in patients with already reduced
MFR as seen in coronary artery disease, particularly before physical
exercise and at high-altitude exposure," Dr. Schindler said. Dr. Schindler
said that further studies will be needed to answer the important questions
raised by this study. Dr. Kaufmann was supported by a grant from the Swiss
National Science Foundation. SOURCE: American College of Cardiology 
-- 
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 ;-)
 Be' almeno prima degli allenamenti sicuramente anch'io!!
Sarebbe poi e' interessante sapere quanto tempo dura questo effetto della
caffeina, mezz'ora, una o due ore???? Perche' almeno un paio di caffe' al
giorno vorrei continuare a prenderli!
gabry
--
Nulla e' bene o male se non si
pensa di fare bene o male
Shakespeare
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Sarà bene che ci provi anch'io!
Era un classico prima delle gare al mattino, visto che non faccio
colazione.
Grazie Fabrizio
Ciao
Mauro