Coffee as medicine? Japanese scientists show how it helps the heart

Five ounces of caffeinated coffee improves blood flow in small blood vessels, Japanese researchers report.
(Mariah Tauger / Los Angeles Times)
<i>This post has been corrected, as indicated below.</i>

The next time you take a coffee break, you might want to consider a triple espresso. The extra caffeine may reduce your risk of dying from cardiovascular disease.

A study presented Wednesday at the American Heart Assn.’s Scientific Sessions meeting offers new evidence that coffee boosts the function of small blood vessels in people who are already healthy.

Researchers in Japan recruited 27 young adults in their 20s to participate in the study. None of them were regular coffee drinkers, but they agreed to consume two 5-ounce cups of joe for the sake of science.


On one of the days, the coffee was caffeinated. On the other day, they drank decaf. They weren’t told which was which. Neither were the researchers, who measured the volunteers’ blood pressure and blood flow after they finished their beverages.

[Updated at 5:15 p.m. PST, Nov. 20: The researchers placed a probe on the tip of each volunteer’s left index finger or thumb and used a technique called laser Doppler flowmetry to measure blood flow to the digit. It works by shining a laser beam through the blood and measuring how much it is scattered by the movement of red blood cells.

For the study, the researchers interrupted blood flow to the hand for one minute, Dr. Masato Tsutsui, the cardiologist who led the study, said in an email to The Times. When the minute was up, they monitored how quickly the normal blood returned to the finger or thumb.]

It turned out that blood flow measured in the finger or thumb was 30% higher on the day they had regular coffee than on the day they had decaf. This was significant because the measurements are a proxy for how well the small blood vessels in the body are working.

That wasn’t the only change. Blood pressure rose “significantly” as well on the days the volunteers drank regular coffee, according to the study abstract. But the caffeine didn’t cause the volunteers’ hearts to beat more quickly.

The researchers also measured levels of the neurotransmitters epinephrine (also known as adrenaline) and norepinephrine in the volunteers’ blood plasma. The levels were essentially the same after drinking both types of coffee.

“This gives us a clue about how coffee may help improve cardiovascular health,” Tsutsui said in a statement from the American Heart Assn. Tsutsui is a professor of pharmacology at the University of the Ryukyus in Okinawa, Japan.

If scientists can figure out how caffeinated coffee helps small blood vessels work better, “it could lead to a new treatment strategy for cardiovascular disease in the future,” he said.

[Updated at 5:15 p.m. PST, Nov. 20: But this is probably not the only reason why many studies have linked coffee consumption with better cardiovascular health, he said via email. Instead, he said, it’s “just one of many.”]

[For the Record, 11:30 pm.m PST, Nov. 20: An earlier version of this story said that extra caffeine from coffee could help get your blood flowing. In the experiment, that only occurred after researchers impeded blood flow in test subjects, not under normal conditions.]

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