According to the Journal of the American Medical Association in 2007:

Small amounts of dark chocolate (one piece of a 16 piece bar of 100g or around 30 calories a day) when taken daily for about 18 weeks can lower blood pressure, which in turn can help reduce the risk of stroke or death from coronary artery disease.

but but but… that is too little. Who can stop after eating just 6 gms of chocolate? I hope eating a few more pieces don’t reverse the good effects of that first one little piece.