A study published last year in the European Heart Journal offers the strongest evidence yet that chronic chocolate consumption reduces blood pressure and lowers the risk of stroke.
This recent evidence comes from the European Prospective Investigation into Cancer (EPIC) study, which followed over 19,000 Germans during the 1990s to see how diet, lifestyle and various health issues affected the risk of cancer. Because of the broad range of data collected by EPIC, it has been possible to mine the database produced by this study to try to answer questions unrelated to cancer - such as whether chocolate confers health benefits.
Investigators report that individuals in the EPIC study who habitually ate an average of 7.5 grams of chocolate per day (about 1/4 ounce) had a 39% reduction in the risk of stroke, compared with individuals who ate no chocolate.
Previous studies have strongly suggested that chocolate with the highest cocoa content (i.e., dark chocolate), and which therefore contains the most flavenoids, can reduce blood pressure and improve vascular function. The EPIC study, which was conducted before anyone raised the possibly counter-intuitive notion that chocolate might be beneficial to health, did not record the type of chocolate its participants consumed.
This more recent study, while adding to previous reports which suggested the same result, does not prove that chocolate consumption is beneficial - it would take a randomized long-term clinical trial to do that. However, since conducting a double-blind randomized controlled clinical trial would require investigators to come up with a "control substance" that looks, feels, and tastes like chocolate, without actually being chocolate, the observational data we have today may be the best data we'll have for a long, long time.
If you choose to take the "chocolate is healthy" message to heart, please be aware of two things. First, the 7.5 grams (1/4 oz) per day of chocolate that conferred the cardiovascular benefit seen in this study is really just a little bit of chocolate. And second, considering that a 3.5 oz chocolate bar contains 500 calories, chronically eating more "normal" portions of chocolate will make you fat, probably negating any health benefits you'd get from the candy.
Buijsse, B, Weikert C, Drogan D et al. Chocolate consumption in relation to blood pressure and risk of CV disease in German adults. Eur Heart J 2010: DOI:10.1093/eurheartj/ehq068.