A study by US and Italian scientists found that eating a 100g bar of dark chocolate every day led to significant improvements in health.
The study involved 19 patients, all of whom had high blood pressure, and found that after two weeks, participants' blood pressure readings had fallen, typically from 142/90mmHg to 137/87mmHg.
The researchers estimate that dark chocolate may therefore reduce deaths from heart attacks and strokes by six per cent.
However, milk chocolate and white chocolate do not have the same health benefits as they do not contain large quantities of naturally-occurring flavanol compounds which protect against heart disease.
The researchers, whose findings are published in the Journal of Nutrition, claimed that flavanol-rich cocoa products "may have a positive impact on cardiovascular risk factors".