WEDNESDAY, Nov. 20, 2013 (HealthDay News) -- Coffee seems to
offer a mysterious benefit to heart health -- one that doctors have
been at pains to explain.
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 percent 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.
These microvessels 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 Association.
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 noninvasive 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
Heart rate levels remained the same between the two groups,
although caffeinated coffee slightly raised blood pressure.
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.
By opening blood vessels and reducing harmful inflammation,
caffeine may create favorable conditions for good heart health, he
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 percent and women's risk by 15 percent.
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 skepticism 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 said.
Data and conclusions presented at meetings typically are
considered preliminary until published in a peer-reviewed medical
For more information on heart health, visit the
U.S. National Library of Medicine.
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