The amount that needs to be eaten seems to vary between the sexes: women can eat just one ounce, or 30g, of chocolate to have the protective effect, while men need to eat between two and six servings a week. A 30g serving is around a third of the standard 100g chocolate bar.
Overall, chocolate reduces the risk by around 23 per cent, researchers from the Danish Diet, Cancer and Health study have found. It's a breakthrough discovery because there's not been an effective way to prevent or treat atrial fibrillation up to now. The problem causes heart flutter and irregular heart rhythm, and affects around 25 per cent of adults at some point in their lives.
Most of the 55,502 participants were eating milk chocolate, which has just 30 per cent cocoa solids, but the researchers recommend eating the healthier dark chocolate, with 70 per cent cocoa, and which has lower levels of fats and sugars.
Other factors could also be at play, including lifestyle choices and diet, but if you've ever needed an excuse to eat chocolate, well, here it is.