The Guardian reports that most of the study's participants ate milk chocolate, not dark chocolate. Since dark chocolate is known for having a higher percentage of protective molecules called flavonoids, the study says this may show that "other compounds, possibly related to milk constituents such as calcium and fatty acids" could lower one's risk of heart disease as well.
There is a caveat, though: as the study was observational, it may not show cause and effect, but rather a circumstantial association. Come on science, don't let us down now! The Guardian does note, however, that the research team found similar benefits to regular chocolate consumption in its review of other published studies.
Dr. Tim Chico, a consultant cardiologist at the University of Sheffield, tells the BBC, "The message I take from this study is that if you are a healthy weight, then eating chocolate (in moderation) does not detectably increase risk of heart disease and may even have some benefit," but, he notes, "I would not advise my patients to increase their chocolate intake based on this research, particularly if they are overweight."