Masato Tsutsui, cardiologist and professor at the University of Ryukyus in Okinawa, Japan, presented a small-scale study that he led – a placebo controlled, randomized crossover – at the American Heart Association’s (AHA's) 2013 Scientific Sessions on November 20.
His team's research suggests drinking caffeinated coffee can improve blood flow in a human finger by 30%, and thus shows how the drink can help improve cardiovascular health.
Tsutsui claims that, until now, no study has looked at the effect of coffee on microvascular (small blood vessel) function, although previous work has linked coffee drinking to lower risk of death from heart disease and stroke.
It has also been found that high doses of caffeine may improve the function of larger arteries.
Decaffeinated coffee had no effect
The results of the unpublished study were presented during a poster session, and involved 27 healthy adults (aged 22-30) who were not regular coffee drinkers.
Each person drank one 5oz cup of either regular or decaffeinated coffee (administered using a double blind) and researchers measured finger blood flow using laser Doppler flowmetry – technology that gauges blood circulation on a microscopic level.
Two days later the tests were repeated using the other coffee, and the researchers noted blood pressure, heart rate and vascular resistance levels.
Blood samples were also taken to analyze caffeine levels and rule out the role of hormones on blood flow, and Tsutsui et al. found that subjects who drank caffeinated coffee had a 30% increase in blood flow (measured over a 75-minute period), compared to those who drank decaffeinated.
Tsutsui said it was still unclear how caffeine works to improve small blood vessel function – improved function has been linked with a lower risk of death from cardiovascular disease – but suggested it may help open blood vessels and reduce inflammation.
“We examined only a small number of subjects, so our findings should be confirmed by a large-scale clinical study,” he added.
Tomaselli's 'take home message'
Gordon Tomaselli, professor of cardiology at Johns Hopkins University School of Medicine, told the AHA that the blood pressure increases in the caffeinated group were one negative in what he said was a small study with “mixed messages”.
“I think the take home message is that there are at least some effects of caffeine on blood vessel function that suggest improvement in blood vessel function, at least in normal subjects,” he said.
Tomaselli warned against extrapolating this study's conclusion to other caffeine delivery vehicles, such as energy drinks.
“I think the only thing we can say right now is that it looks like it may be caffeine, caffeine in coffee that seems to mediate the blood vessel effects. If it's something about caffeine by other means of delivery then you'd actually have to test that,” he said.
The study was part-funded by the All Japan Coffee Association, and you can access the AHA information on the presentation here.