Long-Term Cocoa Flavanol Supplements Do Not Cut Overall Hypertension Risk in Older Adults

Small, short-term studies have suggested that cocoa flavanols lower blood pressure, but a large, long-term trial found that they did not reduce the incidence of hypertension itself. The analysis comes from COSMOS (Cocoa Supplement and Multivitamin Outcomes Study), published in Hypertension by researchers at Brigham and Women's Hospital, Harvard Medical School, in the United States.

8,905 people followed for a median of 3.4 years

COSMOS was a double-blind, placebo-controlled randomized trial that tested cocoa extract (500 mg of flavanols per day, including 80 mg of epicatechin) and a multivitamin in a 2×2 factorial design among 21,442 women aged 65 or older and men aged 60 or older. The researchers analyzed 8,905 participants (mean age 71.1) who did not have hypertension at the start. Over a median of 3.4 years, the incidence of hypertension was 7.1 per 100 person-years in the cocoa group and 7.4 in the placebo group, with no significant difference (hazard ratio 0.96).

In a subgroup analysis, people whose systolic blood pressure was below 120 mmHg at baseline had a 24% lower risk of developing hypertension in the cocoa group, and this difference became clear from the second year after assignment. People with 120 to 139 mmHg showed no difference.

The subgroup results are hypothesis-level and need separate validation, and the diagnosis of hypertension included self-reported diagnoses. Some of the researchers disclosed funding from a company that donated the study products.