By improving glucose-insulin metabolism, regular consumption of cocoa flavonol may improve cognitive function in older adults with mild cognitive impairment (MCI)….
First author Giovambattista Desideri, MD, director of the Geriatric Division, Department of Life, Health and Environmental Sciences, University of L’Aquila in Italy, stated that, "Given the global rise in cognitive disorders due to the ‘graying’ of populations in Western countries, our findings provide encouraging evidence that consuming cocoa flavonols could represent a fascinating new tool for preserving/improving cognitive function during senescence.
Mary Ann Johnson, PhD, national spokesperson for the American Society of Nutrition (ASN), who was not involved in the study, stated that, "There is great interest in identifying nutritional factors that could potentially delay or prevent conversion of MCI to dementia."
What makes this study novel, she said, is that it is a randomized controlled trial in people with MCI, it employed well-known cognitive tests, and it used 3 levels of cocoa flavonols: low, medium, and high.
"Both the medium and high levels conferred some benefits to cognition, insulin resistance, and blood pressure. Poor cognition, poor insulin resistance, high blood pressure, and other cardiovascular risk factors have all been linked to dementia," Dr. Johnson said.
Based on prior studies, intake of flavonoids may be associated with a decreased risk for incident dementia, a lower prevalence of cognitive impairment, and better cognitive evolution over 10 years in aging adults, the authors note.
To investigate further, Dr. Desideri and colleagues recruited 90 elderly individuals with MCI into the Cocoa, Cognition and Aging (CoCoA) Study. They were randomly assigned to consume once daily for 8 weeks a drink containing 1 of 3 levels of cocoa flavonols: 990 mg, the high flavonol (HF) group; 520 mg, the intermediate flavonol (IF) group; or 45 mg, the low flavonol (LF) group.
The team assessed cognitive function and a verbal fluency test. Baseline performances on these 3 tests were similar. During the study period, the researchers did not see any significant changes in MMSE scores in relation to group assignment.
However, the time needed to complete the TMT A did change significantly during the study period (P < .0001), with significant reductions observed in participants in the HF group (-14.3 seconds; P < .0001) and IF group (-8.8 seconds; P < .0001) but not in those in the LF group (+1.1 seconds; P = .65).
The results were similar for the TMT B test, with significant reductions in the time needed to complete the test seen in the HF and IF groups (-29.2 and -22.8 seconds, respectively; for both, P < .0001) but not in the LF group (+3.8 seconds; P = .21).
As a result, TMT A and B scores at the end of follow-up were significantly (P < .05) better in the HF and IF groups than in the LF group, the authors note.
Additionally, they say verbal fluency test scores significantly improved (P < .0001) during the study, with improvements seen in the HF group (+8.0 words per 60 seconds; P < .0001) and IF group (+5.1 words per 60 seconds; P < .0001) and, to a lesser extent, in the LF group (+1.2 words per 60 seconds; P < .014).
The improvement of verbal fluency test score was significantly greater in HF participants than in those assigned to the LF group (P < .05).
Baseline blood pressure and metabolic parameters were similar in the 3 groups, but with treatment, HF and IF groups experienced a decrease in insulin resistance, blood pressure, and lipid peroxidation.
Dr. Desideri and colleagues report that changes in homeostasis model assessment–insulin resistance (HOMA-IR) were the main determinants of change in cognitive function, accounting for roughly 40% of composite z score variability throughout the study period (P < .0001).
Changes in systolic blood pressure levels and plasma isoprostane concentrations accounted for only 2% and 7% of cognitive improvement, respectively, throughout the study period.
"Our data suggest that regular cocoa flavonol consumption, in the context of a calorie-controlled and nutritionally balanced diet, might represent an effective strategy in preserving brain and cardiovascular health and function," Dr. Desideri concluded. "Obviously, larger studies are needed to validate our findings."
The researchers caution that the intervention lasted only 2 months; therefore, the extent of the cognitive benefits and their duration, as well as their impact on a clinical course of MCI, remain to be established.
It is also unclear whether the observed benefits in neurocognition are a direct consequence of cocoa flavonols themselves or a secondary effect related to general improvements in cardiovascular function or health.
Finally, the study team points out that the participants in the study were generally in good health and were free of cardiovascular disease and therefore may not be completely representative of all individuals with MCI.
Published online August 14, 2012 in Hypertension