Coffee seems to offer a
mysterious benefit to heart health – one that doctors have been at pains to
Now, a small, new study
from Japan suggests that the caffeine in a cup of coffee might help your small
blood vessels work better, which could ease strain on the heart.
A cup of caffeinated coffee
caused a 30% increase in blood flow through the small vessels of people's
fingertips, compared with a cup of decaf, according to the research, which is
scheduled for presentation Wednesday at the American Heart Association's annual
meeting in Dallas.
regulate the ease with which blood flows through the circulatory system and the
body's tissues, said lead researcher Dr Masato Tsutsui, a cardiologist and
professor in the pharmacology department at the University of the Ryukyus, in
Previous studies have shown
an association between coffee drinking and lower risk of heart attack, heart
disease and stroke, said Dr Gordon Tomaselli, chief of cardiology at the Johns
Hopkins University School of Medicine. Researchers found that high doses of
caffeine may improve the function of larger arteries.
But scientists have not
been able to figure out why this is, given that coffee also can increase blood
pressure. High blood pressure can damage arteries.
"This is an intriguing
observation that may help us understand why consumption of coffee may be
beneficial," said Tomaselli, former president of the American Heart
Finger blood flow
The study involved 27
healthy adults, aged 22 to 30, who did not regularly drink coffee. They were
asked to drink a 5-ounce cup of either caffeinated or decaffeinated coffee.
Researchers then measured their finger blood flow using a non-invasive laser
technique for gauging blood circulation.
Two days later, the
experiment was repeated with the other type of coffee. Neither the researchers
nor the participants knew when they were drinking caffeinated coffee.
The researchers found that
blood flow in the small blood vessels improved by nearly one-third among the
people who drank caffeinated coffee. The effect continued in those people over
a 75-minute period.
Heart rate levels remained
the same between the two groups, although caffeinated coffee slightly raised
The improved blood flow is
likely because of improved function of the inner lining of the blood vessels,
Tsutsui said. Researchers have linked the function of the lining of blood
vessels – also known as endothelial function – to future heart attacks, heart
disease and strokes.
Reducing harmful inflammation
By opening blood vessels
and reducing harmful inflammation, caffeine may create favourable conditions
for good heart health, he said.
But how much coffee is too
much? Tsutsui pointed to a landmark U.S. National Institutes of Health study
that showed that, overall, drinking six or more cups of coffee a day reduced
men's risk of early death by 10% and women's risk by 15%.
That study, published last
year in the New England Journal of Medicine, found that risk of heart
disease and stroke either remained low or went even lower as people drank more
coffee during the day.
The new study was
co-sponsored by the All Japan Coffee Association, which might raise some
healthy scepticism were it not for the large body of evidence that already
shows coffee's heart health benefits, Tomaselli said.
That said, the study's
small sample size does not conclusively explain why coffee is so good for the
heart. "I don't think this answers any questions for us," Tomaselli
Data and conclusions
presented at meetings typically are considered preliminary until published in a
peer-reviewed medical journal.
For more information on
heart health, visit the US National Library of Medicine.