One or two servings of good-quality dark chocolate a week reduced the risk of middle-aged and elderly women developing the condition by almost a third, a study found.
Scientists looked at the association between chocolate and heart failure in almost 32,000 Swedish women aged 48 to 83.
A typical chocolate bar weighs around 100 grams, but the amount of healthy cocoa solids it contains varies greatly. Dark chocolate can contain as much as 75% cocoa while standard milk chocolate may have 20% or less.
Antioxidant plant compounds called flavonoids in cocoa are believed to protect against heart disease and high blood pressure. The study authors pointed out that chocolate eaten in Sweden tends to have a high cocoa content while around 90% of chocolate consumed in the UK is milk chocolate, it consists of around 30% cocoa solids.
The research was carried out by the Cardiovascular Epidemiology Research Unit at the Beth Israel Deaconess Medical Centre in Boston, US.