In April 2017 researchers from Australia published their review of the scientific literature to assess the effect of chocolate and cocoa products on blood pressure levels. A total of 35 articles were included in the review. Results showed that there was a small but statistically significant blood pressure-reducing effect of flavanol-rich cocoa products when compared with placebo. While systolic blood pressure was reduced by approximately 4 mmHg in hypertensive individuals and also tended to be lowered in prehypertensive individuals, there was no significant difference in individuals with normal blood pressure levels. It is not known whether the age of participants played a role in the effect of cocoa on blood pressure, with younger participants responding with a greater reduction in blood pressure levels, and this needs to be further investigated.
Ried K et al. Effect of cocoa on blood pressure. Cochrane Database Syst Rev. 2017 Apr 25;4:CD008893.