A cup of coffee might provide a jolt of energy -- and a potential boost to your blood vessels.
Research presented Nov. 20 at the American Heart Association's Scientific Sessions 2013 shows that drinking just one cup of coffee was able to improve the blood flow in the subject’s finger. This was an indication that the inner linings of the small blood vessels were functioning better.
"This gives us a clue about how coffee may help improve cardiovascular health," lead researcher Dr. Masato Tsutsui, a cardiologist and professor in the pharmacology department at the University of the Ryukyus in Okinawa, Japan, said in a press release.
The study looked at 27 healthy adults between 22 and 30 who were not regular coffee drinkers. They were told to drink one 5-ounce cup of either caffeinated or decaffeinated coffee. Then, two days later, the subjects switched and were given the other kind of coffee to drink.
Blood flow was determined with laser Doppler flowmetry, a device which shines a laser through the blood and then measures how red blood cells move in relation to the beam. The subjects also had their blood pressure, heart rate, and vascular resistance levels measured, and had blood samples taken to measure the amount of caffeine and to rule out hormonal influences.
Those that got a dose of caffeine had a 30 percent increase in blood flow over a 75-minute period compared to when they had a decaffeinated cup of coffee.
Caffeinated coffee also increased blood pressure but the heart rate was similar no matter which beverage was consumed.
The researchers are unclear why caffeine has this affect on blood flow, but they believe the compound might help open blood vessels and cut down on inflammation.
"If we know how the positive effects of coffee work, it could lead to a new treatment strategy for cardiovascular disease in the future," Tsutsui said.
Dr. Vincent Bufalino, a cardiologist and senior vice president for the Advocate Cardiovascular Institute in Chicago, told USA Today that people shouldn’t jump to conclusions about the benefits of coffee because this study is just based on one cup.
"Small amounts of coffee may have a benefit, but a higher consumption of coffee definitely raises blood pressure. It definitely raises heart rate, and it makes you more prone to heart palpitations," Bufalino says. "We see that every day in terms of the use of caffeine in patients. A lot of people sense that a cup of coffee gives them a lift but too much can have negative effects."
Other research has shown that too much coffee -- about four cups a day -- may raise the risk of earlier death in younger adults.
Then again, research has shown that two cups of coffee daily may lower suicide risk by almost 50 percent and heavy coffee drinkers who drank four or more cups of coffee a day were shown to have a lower risk of developing oral cancer.
© 2013 CBS Interactive Inc. All Rights Reserved.