I always had a poor view of the healthfulness of chocolate, but recently I came across an 8fact image which says otherwise:
Is it true that eating dark chocolate reduces the risk of heart diseases by one third?
In several studies, chocolate consumption was associated with decreased risk of heart disease. Association does not already mean the cause-effect relationship, though.
The supposedly beneficial nutrients in chocolate are flavonoids, which are found in higher amounts in dark than in milk chocolate.
PubMed Central (2012)
Cocoa and particularly dark chocolate are rich in flavonoids and recent studies have demonstrated blood pressure lowering effects of dark chocolate....consumption of chocolate is inversely related with prevalent coronary heart disease in a general population.
The acute ingestion of both solid dark chocolate and liquid cocoa improved endothelial function and lowered blood pressure in overweight adults.
Dark, but not white, chocolate decreases blood pressure and improves insulin sensitivity in healthy persons.
In other studies, no effect of chocolate on heart disease was identified:
...chocolate specifically was not shown to affect risk of coronary heart disease.
This investigation failed to support the predicted beneficial effects of short-term dark chocolate and cocoa consumption on any of the neuropsychological or cardiovascular health-related variables.
or insufficient evidence:
PubMed Central (2006)
...flavonoids are likely protective against coronary heart disease mortality. The highest priority now is to conduct larger randomized trials to definitively investigate the impact of chocolate consumption on long-term cardiovascular outcomes.
Cochrane Summaries (Meta-analysis of 20 studies, 2012)
the effect of cocoa products on blood pressure in adults when consumed daily for a minimum of two weeks...a small but statistically significant blood pressure reducing effect of -2.8 mm Hg systolic and -2.2 mm Hg diastolic...more trials are required.
My conclusion: When the effects of dark chocolate in some studies seem to be small and of questionable clinical significance (a relatively small drop--2.8 mm Hg--of blood pressure) and inconsistent (no benefits in some studies), for me, there is insufficient evidence about the beneficial effects of dark chocolate on heart disease.