Coffee may perk up the blood vessels due to the effects of caffeine, a study suggests.
Researchers found that drinking a cup of caffeinated coffee significantly improved blood flow in the fingers of 27 healthy adults.
Measuring blood flow in the finger provides an indication of how well the body's smaller blood vessels are functioning.
Comparing normal-strength coffee with decaf, the caffeinated version increased blood flow by 30% over a 75-minute period.
Professor Masato Tsutsui, a heart expert from the University of the Ryukyus in Okinawa, Japan, said: "This gives us a clue about how coffee may help improve cardiovascular health."
He presented the findings at the American Heart Association's Scientific Sessions meeting in Dallas, Texas.
The study participants were all people aged from 22 to 30 who did not regularly drink coffee.
A laser technique was used to study blood circulation in the finger on a microscopic level non-invasively.
Volunteers were randomly assigned to drink caffeinated or decaffeinated coffee without knowing what they had been given. Two days later, each group had its coffee allocation swapped and the study was repeated.
Caffeinated coffee caused a slight increase in blood pressure and improved the functioning of cells lining blood vessel walls, the researchers found.
The study was part-funded by the All Japan Coffee Association.