say researchers in the BMJ who conducted a meta-analysis.
"Based on observational evidence, levels of chocolate consumption seem to be associated with a substantial reduction in the risk of cardiometabolic disorders. Further experimental studies are required to confirm a potentially beneficial effect of chocolate consumption." 
Of course, making it Fairtrade, makes it even better for you!
1. Buitrago-Lopez A, Sanderson J, Johnson L, Warnakula S, Wood A, Di Angelantonio E, Franco OH. Chocolate consumption and cardiometabolic disorders: systematic review and meta-analysis. BMJ 2011;343:d4488. Available from: http://www.ncbi.nlm.nih.gov/pubmed/21875885