Coffee may do more than wake you up. It may help your small blood vessels work better, a small new study suggests.

But that doesn’t mean you should guzzle gallons of java.

Previous research has shown that moderate coffee consumption may have some beneficial effects on cardiovascular health. However, the precise mechanism for this benefit is unknown, says Masato Tsutsui, one of the authors of the new research and a cardiologist and professor in the pharmacology department at the University of the Ryukyus in Okinawa, Japan.

Tsutsui and colleagues in Japan worked with 27 healthy adults, ages 22 to 30, who did not regularly drink coffee. On one day, each participant drank one five-ounce cup of either regular caffeinated or decaffeinated coffee. Then researchers measured reactive hyperemia in the participants’ left index fingers. This is a measure of vascular function that takes into consideration how well small blood vessels function. Two days later the researchers repeated the procedure with the other type of coffee.

Findings presented last week at an American Heart Association meeting in: Those who drank a cup of caffeinated coffee had a 30 percent increase in vascular function in the index finger during a 75-minute period, compared to those who drank decaffeinated coffee.

Caffeinated coffee slightly raised participants’ blood pressure and decreased finger blood flow, compared with decaf.

Heart rate levels were the same in those who drank decaf or regular coffee.

Tsutsui says caffeine may improve blood vessels’ function. The study was funded in part by the All Japan Coffee Association.

However, cardiologist Vincent Bufalino, a spokesman for the heart association and senior vice president for the Advocate Cardiovascular Institute in Chicago, says “it’s hard to come to broad-based scientific conclusions based on this one small study. The research is limited to one cup of coffee.”