Foods like dark chocolate, which contain plenty of cocoa, may potentially reduce high blood pressure by acting in a manner similar to many blood pressure-lowering drugs, according to an analysis of previous studies by German researchers.
Researchers from the University Hospital of Cologne examined data of five cocoa studies and five tea studies and concluded that dark chocolate and other cocoa-rich foods acted to reduce high blood pressure better than tea.
The details of the study appear in the April 9 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
Dark chocolate contains a high amount of cocoa and is also rich in elements called flavonoids. These compounds are known to reduce cholesterol levels in blood vessels. Flavonoids are also found in tea, red wine and some fruits and vegetables.
Flavonoids also slow the grouping of "bad" LDL cholesterol besides rendering blood platelets less likely to clump and cause clots. In a previous study Dr. Norman Hollenberg of Brigham and Women's Hospital in Boston reported that flavanols may be associated with nitric oxide, which regulates the arteries and is critical for healthy blood flow and pressure.
Current guidelines for people with high blood pressure advise a diet rich in fruits and vegetables. These eatables are high in polyphenols, which are thought to protect against heart disease and high blood pressure.
The background information of today's article says that although tea and cocoa products account for the major proportion of total polyphenol intake in Western countries, they are not part of the cardioprotective or anti-hypertensive dietary advice.
Dirk Taubert, M.D., Ph.D., and colleagues at the University Hospital of Cologne, reviewed previously conducted trials to gauge the benefits of cocoa and tea in reducing high blood pressure.
There were 173 participants in the five cocoa trials, while the tea trials involved both green tea and black tea and had 343 participants. All studied took place between 1966 and 2006 and lasted for at least a week. Hypertension was defined as having a systolic and diastolic blood pressure greater than 140 and 90 mm of Hg (mercury).
All studies were randomized placebo-controlled trials, or used a crossover design. The latter design means that the blood pressure of participants was assessed both before and after consuming cocoa and tea.
In the cocoa trials, 87 participants were assigned to consume cocoa, while 86 were controls. Among the 173 participants, 34 percent had high blood pressure. Researchers report a two-week follow-up of these patients after which both systolic and diastolic blood pressure was lowered in the group consuming cocoa.
Systolic blood pressure dropped by an average of 4.7 mmHg and diastolic blood pressure by 2.8 mmHg, the researchers reported.
But no such benefits were reported from the tea studies where 171 participants were drinking tea and 172 acted as controls.
"At the population level, a reduction of four to five mm Hg in systolic blood pressure and two to three mm Hg in diastolic blood pressure would be expected to substantially reduce the risk of stroke, coronary heart disease, and all-cause mortality," the researchers write.
In fact researchers theorized a 20 percent reduction in stroke risk, a 10 percent reduction in risk of coronary heart disease and an 8 percent reduction in all-cause mortality.
Although tea and cocoa contain polyphenols in high quantities, black and green tea contain more flavan-3-ols, while cocoa is rich in compounds called procyanids. These procyanids control blood pressure in a better manner. The Reviewers said
tea phenols appeared to be less active than cocoa polyphenols.
"This suggests that the different plant phenols must be differentiated with respect to their blood pressure-lowering potential and thus cardiovascular disease prevention," they added.
Dr Taubert, the lead researcher cautioned the jury was still out as far as the potential benefits of large-scale cocoa consumption was concerned. "In the studies we reviewed, the blood pressure results occurred with cocoa doses above the habitual intake and were observed only in the setting of short-term interventions," he said.
"It is not known whether long-term intake of small habitual amounts of cocoa, such as a small bar or piece of chocolate per day, may also cause significant blood pressure effects."
Researchers also warned the study was not a recommendation to consume large amounts of chocolate since they are still loaded with calories. "Rationally applied, cocoa products might be considered part of dietary approaches to lower hypertension risk," they concluded.
Many confectionary companies are already researching methods to make their chocolate flavonoid-rich. Mars, Incorporated, the world leader in chocolate production has been able to incorporate these flavanols into their chocolates.
While a little dark chocolate is good, a lot is not necessarily healthy. Consumers must be aware that chocolate still is loaded with calories. If it is consumed in large amounts, other dietary adjustments must be made. But at the end of the day a balanced diet with plenty of exercise is the best way to maintain a healthy heart.