Flavanols found in cocoa have been associated with blood pressure lowering properties due to their stimulation of nitric oxide dependent vasodilation. In this review we assessed the effect of cocoa products on blood pressure in adults when consumed daily for a minimum of two weeks.
Trials were of short duration, all but one trial were between two and eight weeks long (n=1 of 18 weeks). While a significant effect with trials of two weeks duration (n=9) was evident, it was not with trials of longer duration (n=11). It is not clear whether this result is directly attributable to the trial length or may be due to another factor such as the type of control group used in the shorter trials or the level of blinding of participants to the treatment. While analysis of trials using a flavanol free control group indicated a significant effect on blood pressure, analysis of trials using a low flavanol control group did not.
Adverse effects including gastrointestinal complaints and distaste of the trial product were reported by 5% of patients in the active cocoa intervention group and 1% of patients in the control groups.
Although we did further analyses and explored other subgroups for an effect (including by age, body mass index and baseline blood pressure; sugar content of the cocoa product), the results of all subgroup analyses, and any measured association of effect, need to be tested, and confirmed or refuted, in further trials.
The small reduction in blood pressure of about 2-3 mm Hg observed in the pooled trials overall might complement other treatment options and might contribute to reducing the risk of cardiovascular disease. However, we were unable to identify any randomized, controlled trials that tested the effect of long-term daily ingestion of cocoa products on blood pressure and there were no trials that measured an effect on clinical outcomes related to high blood pressure such as heart attacks or strokes.
More trials in which the intake of low flavanol dosages are compared with flavanol-free controls are required to test whether low dosages are effective in reducing blood pressure. In addition, longer term trials are needed to elucidate whether regular consumption of flavanol-rich cocoa products has a beneficial effect on blood pressure and cardiovascular health over time, and whether there are any potential adverse effects of long-term ingestion of cocoa products on a daily basis.