It also found reduced levels of blood pressure and cholesterol – a waxy substance found in the blood that can lead to a hike in heart attack risk.
The two studies were both carried out by the EU-funded Flaviola Research Consortium, and, commenting on the findings, Flaviola director Professor Malte Kelm, from the University Hospital Dusseldorf, said: “With the world population getting older, the incidence of cardiovascular disease, heart attacks and stroke will only increase.
“It is therefore pivotal that we understand the positive impact diet can have on cardiovascular disease risk. As part of this, we want to know what role flavanol-containing foods could play in maintaining the health of the heart and blood vessels.
“Our results indicate flavanols may have preventive potential for CVD.”