Summary: Study reveals cocoa powder reduces blood pressure and arterial stiffness, only when levels of both are elevated.
Source: University of Surrey
Cocoa only reduces blood pressure and arterial stiffness when elevated, a new study from the University of Surrey finds.
Cocoa flavanols have previously been found to lower blood pressure and arterial stiffness as much as some blood pressure medication. However, how effective flavanols are in everyday life in reducing blood pressure has remained unknown, as previous studies in this area have been performed in tightly controlled experimental settings.
Surrey’s new research reduces concerns that cocoa as a treatment for raised blood pressure could pose health risks by decreasing blood pressure when it is not raised, paving the way for it to be potentially used in clinical practice.
In the first study of its kind study, researchers set out to investigate the use of flavanols, a compound found in cocoa, in lowering blood pressure and arterial stiffness in individuals outside of clinical settings.
Christian Heiss, Professor of Cardiovascular Medicine at the University of Surrey, said:
“High blood pressure and arterial stiffness increases a person’s risk of heart disease and strokes, so it is crucial that we investigate innovative ways to treat such conditions.
“Before we even consider introducing cocoa into clinical practices, we need to test if the results previously reported in laboratory settings safely translate into real-world settings, with people going about their everyday lives.”
For several days, eleven healthy participants consumed, on alternating days, either six cocoa flavanol capsules or six placebo capsules containing brown sugar. Participants were provided with an upper arm blood pressure monitor and a finger clip measuring pulse wave velocity (PWV) which gauges levels of arterial stiffness.
Measurements of blood pressure and PWV were taken prior to consumption of the capsules and every 30 minutes after ingestion for the first three hours, and then hourly for the remaining nine hours. Researchers found that blood pressure and arterial stiffness were only lowered in participants if it was high, and there was no effect when the blood pressure was low in the morning.
Significantly, effects were also, for the first time, identified at eight hours after cocoa was consumed. Researchers believe that this second peak may be due to how bacteria in the gut metabolise cocoa flavanols.
Professor Heiss added:
“The positive impact cocoa flavanols have on our cardiovascular system, in particular, blood vessel function and blood pressure, is undeniable. Doctors often fear that some blood pressure tablets can decrease the blood pressure too much on some days.
“What we have found indicates that cocoa flavanols only decrease blood pressure if it is elevated. Working with participants’ personal health technologies showed us how variable blood pressure and arterial stiffness can be from day to day and shows the role of personal health monitors in developing and implementing effective personalized care.”
Assessing Variability in Vascular Response to Cocoa With Personal Devices: A Series of Double-Blind Randomized Crossover n-of-1 Trials
Controlled clinical intervention studies have demonstrated that cocoa flavanols (CF) can decrease blood pressure and arterial stiffness in healthy humans, although a large variability in the effect size across trials has been reported.
In this study, we evaluated the intra- and inter-individual variability of responses to CF in everyday life using a series of n-of-1 trials in healthy free-living individuals with normal blood pressure carrying personal devices.
In total, eleven healthy young humans participated in a repeated crossover randomized controlled double-blind n-of-1 trial. On 8 consecutive days, each volunteer consumed on alternating days 6 CF capsules (862 mg CF) on 4 days and 6 matched placebo capsules (P, 0 mg CF/day) on another 4 days in one of the two randomized sequences (CF-P-CF-P-CF-P-CF-P or P-CF-P-CF-P-CF-P-CF). On each day, the capsules were taken at the same time in the morning with breakfast after baseline measurements.
Each subject was provided with an upper arm blood pressure monitor and a finger clip that measures pulse wave velocity (PWV). Measurements of blood pressure, heart rate, and PWV were taken at least hourly over 12 h during the day by the participants.
On the first 2 days, measurements were performed under supervision to provide training. The overall mixed model analysis showed that CF significantly decreased 12-h systolic blood pressure and PWV by −1.4 ± 0.3 mmHg and −0.11 ± 0.03 m/s, respectively.
Peak effects were observed within the first 3 h (1.5 h SBP: −4.9 ± 2.2 mmHg, PWV: −0.32 ± 0.17 m/s) and again after 8 h post-ingestion. Large inter-individual variation in responses was found [intra-cluster correlation coefficients (ICC): 0.41, 0.41].
When analyzing single individuals’ datasets, there was also considerable between-day variation in individual responses that varied greatly between subjects (ICC: 0–0.30, 0–0.22, 0–0.45). Effect sizes inversely correlated with baseline blood pressure values both between- and within-subjects.
The data confirm that cocoa can decrease blood pressure and arterial stiffness in everyday life when elevated within the normal range. The large inter- and intra-individual variation in responses calls for more personalized nutritional intervention strategies.