There have been three studies released recently, dealing with the effects of coffee, coffee and tea, and chocolate on the heart. The studies variously showed a small reduction in both systolic and diastolic blood pressure or a reduced risk of heart failure. Once again, these studies are suggestive, but larger and more complete studies are necessary to reach a firm conclusion. And let us not lose sight of the fact that none of the studies showed the consumption of coffee or tea or chocolate to have a deleterious effect on heart function or blood pressure. The benefit of chocolate is presumed to be the result of flavanol in the chocolate; this compound increases the formation of nitrous oxide and thereby dilates the arteries ( much as Viagra does).
One study was done by Dr. Karen Ried of the University of Melbourne, Australia. This was a review of 20 short term studies involving over 900 volunteers. The studies lasted 2 weeks, 8 weeksa, or 18 weeks.They ate 100 gm of chocolate daily, and averaged a 3mm drop in systolic pressure and a 2mm drop in diastolic. One study showed a drop of 4mm and 3 mm, respectively. This is the same effect you would see from daily exercise or a heart-healthy diet. The control group showed no such decrease. The article also mentioned the Kuma Indians of South America who average 4 cups of cocoa a day and have remarkably good blood pressure.
Another study was a meta-analysis of 5 studies. There was a j-shaped curve relating the consumption of coffee to heart failure. The biggest "protection" against heart failure came with those who averaged 3 to 5 cups of coffee a day. The results of this study might make one reconsider the recommendations against coffee consumption in certain patients.
The final study was a French retrospective analysis of over 175,000 patients ranging in age from 16 to 95 years with regard to their consumption of tea or coffee. They subdivided the patients into 3 groups: no coffee or tea, one to four cups a day, and more than four cups daily. In those drinking 1-4 cups a day, there was a small decrease in systolic blood pressure, in pulse pressure, and in pulse rate. The effect was small, but it is suggestive.
To me the take away message from these studies is that there is no evidence that the consumption of tea, coffee or chocolate is detrimental, and it may in fact be beneficial.