Chocolate on the Brain: MRI study shows cocoa boosts cognitive function

For older people showing signs of cognitive impairment, doctors could one day prescribe a daily dose of chocolate. New research shows regular cocoa consumption in the elderly led to significantly better neuronal metabolic function and blood flow, and subsequently improved cognition, according to a study published August 7 in Neurology.

Farzaneh A. Sorond, MD, PhD, from the department of neurology, stroke division, at Brigham and Womens Hospital in Boston, and colleagues tested their theory that cocoa, which is known to be rich in flavanols and which was previously shown to protect circulatory health and brain function, could alter an integral relationship between neuronal activity and blood flow that is implicated in pathology when it goes awry. Researchers wondered if cocoa-derived flavanols might have a beneficial effect on this functional and spatial relationship of metabolism and blood flow in the brain, called neurovascular coupling (NVC), when it is out of whack. They were right and matched these results with previous studies.

“Our study shows that NVC is modifiable and can be enhanced with cocoa consumption,” wrote Sorond et al. “This finding is supported by the effect of cholinesterase inhibitors on NVC in patients with [Alzheimer’s disease.]”

For this study, 60 people around the age of 73 underwent a concurrently phased, double-blind clinical trial assessing NVC and mental performance at the outset of the study, after consuming cocoa for 24 hours and also after two cups a day of either high flavanol or low-flavanol cocoa for 30 days. Patients were evaluated for parameters of cognition using the Mini-Mental State Examination and the Trail Making Test A and B, which tests a person’s gait. Beat-to-beat blood flow velocity was used to measure NVC in the middle cerebral arteries in conjunction with the N-Back Task, which tests for fluid intelligence. The structural integrity of cerebral white matter was also evaluated with MRI.

After 30 days of chocolate consumption in liquid form, researchers found that cocoa intake was connected with about 5 percent higher levels of NVC in patients with cognitive impairment. Trails B score times were improved with NVC from about 167 seconds down to about 116 seconds, and results of the 2-Back Task were also positively affected. Additionally, raised NVC was matched with significantly more viable white matter. 

“There is a strong correlation between neurovascular coupling and cognitive function, and both can be improved by regular cocoa consumption in individuals with baseline impairments,” wrote the authors. “Better neurovascular coupling is also associated with greater white matter structural integrity.”

Further studies, such as those involving PET or functional MRI, are needed for researchers to get a better understanding of the relationship between dietary cocoa and improved cerebral blood flow and its effect on cognitive performance. A wild card remains as scientists aren’t completely sure why patients who drank low-flavanol cocoas still showed significant improvements in NVC.

“Given our prior work establishing the beneficial effects of cocoa flavanols on systemic and cerebral vascular function, we were surprised to observe the equivalence of neurovascular responses between flavanol-rich and flavanol-poor cocoa subgroups in our study,” the researchers wrote. “Improvements in NVC were present in both groups. One possible explanation is that the previously reported responses to flavanol-rich cocoa were not entirely driven by flavanols, but another component(s) of cocoa. Alternatively, it is conceivable that the regulation is so exquisitely sensitive to flavanols that even the slight amounts contained in the flavanol-poor drink were sufficient to improve NVC.”