The small amount of caffeine found in a cup of coffee could have a negative effect on the walls of blood vessels, according to new research.
Researchers from the Athens Medical School in Greece, led by Dr Charalambos Vlachopoulos, told delegates at the annual meeting of the American Society of Hypertension that individuals suffering from mild hypertension were shown to have a temporary increase in blood pressure after consuming just 250mg of caffeine. They also experienced a stiffening of the aorta, the main vessel carrying blood from the heart.
Vlachopoulos' team also looked at the effects of caffeine consumption on individuals with normal blood pressure, and found that they too experienced a stiffening of the blood vessel walls.
While the effects of the caffeine were only temporary, blood pressure levels remained elevated for as long as three hours after participants took the caffeine pills, the researchers noted.
Both studies focused on a very small number of patients, and Vlachopoulos stressed that more research was needed to confirm the results. However, the Greek studies suggest that even relatively low doses of caffeine, two or three cups a day, could lead to increased hypertension among individuals already suffering from high blood pressure, and increase the risk of a more serious problem such as a heart attack or a stroke.