Cocoa, Even With Few Flavonoids, Boosts Cognition

Drinking cocoa, whether rich in flavonoids or not, appears to boost the effect of blood flow on neuronal activity in the brain, known as neurovascular coupling (NVC).

A new study shows not only that drinking flavonoid-rich or flavonoid-poor cocoa improves NVC but also that higher NVC is associated with better cognitive performance and greater cerebral white matter structural integrity in elderly patients with vascular risk factors.

As researchers search for ways to detect dementia at the earliest possible stage, the study results could pave the way for using NVC as a biomarker for vascular function in those at high risk for dementia, said lead author Farzaneh A. Sorond, MD, PhD, Department of Neurology, Stroke Division, Brigham and Women's Hospital, Boston, Massachusetts.

"Our study shows that NVC is modifiable and can be enhanced with cocoa consumption," said Dr. Sorond.

The study is published online August 7 in Neurology.

Tight Correlation
The double-blind proof-of-concept study included 60 community-dwelling participants, mean age 72.9 years. About 90% of the participants were hypertensive, but with well-controlled blood pressure, and half had diabetes mellitus type 2 with reasonably good control. Three quarters were overweight or obese.

Participants were randomly assigned to 2 cups a day of cocoa rich in flavonoids (609 mg per serving) or cocoa with little flavonoids (13 mg per serving). Diets were adjusted to incorporate the cocoa, each cup of which contained 100 calories. Participants were also asked to abstain from eating chocolate.

Researchers measured cerebral blood flow in these participants using transcranial Doppler ultrasonography. Among other things, they documented changes in the middle cerebral artery and blood flow velocity at rest and in response to cognitive tasks (NVC).

The study showed that NVC was tightly correlated with cognition; scores for Trail making Test B, a test of executive function, were significantly better in those with intact NVC (89 seconds vs 167 seconds; P = .002). Participants with intact NVC also had significantly better performance on the 2-Back Task, a test for both attention and memory (82% vs 75%; P = .02).

"The higher you increase your blood flow during a cognitive task, the better your cognitive performance," commented Dr. Sorond, adding that this is something that has never been shown before.

NVC was also correlated with cerebral white matter structural integrity. Higher NVC was associated with overall less white matter macro- and micro-structural damage. In general, those with intact NVC had a greater volume of normal white matter and smaller volume of white matter hyperintensities, higher fractional anisotropy, and lower mean diffusivity in the normal white matter and WMH.

Therapeutic Target
These results suggest that NVC could be an important therapeutic target. But before NVC can be considered a biomarker, it has to be shown to be changeable, and the clinical importance of the modification must be shown.

To that end, the study authors opted to use cocoa. They could have chosen many other potential modifiers but chose cocoa because the literature has shown the beneficial effects of cocoa on brain health and also because it's something that many people enjoy, said Dr. Sorond.

The study found that blood pressure, blood flow, and change in NVC were not significantly different between the 2 cocoa groups. In the combined cocoa groups, 30-day blood pressures were not significantly different from baseline (P > .5).

In contrast, response to cocoa differed significantly depending on NVC status. Cocoa had a significant effect on NVC in those with impaired (<5%) coupling at baseline. Of those with impaired NVC, 89% responded to 30 days of cocoa consumption and increased NVC compared with only 36% of those with intact NVC (P = .0002). In those with impaired baseline coupling, cocoa consumption was associated with an 8.3% (P < .0001) increase in NVC at 30 days.