Past evidence suggests eating flavonoids, polyphenic compounds from plant-based foods, may confer cardiovascular benefits. Flavonols are a subclass of these compounds that are abundant in tea, grapes, red wine, apples, and cocoa products including chocolate.
In a double-blind study, elderly patients with mild cognitive impairment who consumed high or moderate levels of cocoa flavanols for 2 months had significant improvements on certain cognitive assessment tests compared with those who took in only small amounts, Giovambattista Desideri, PhD, of the University of L'Aquila in Italy, and colleagues reported online in Hypertension.
"Although additional confirmatory studies are warranted, the findings...suggest that the regular dietary inclusion of flavanols could be one element of a dietary approach to the maintaining and improving not only cardiovascular health but also specifically brain health," they wrote.
So to assess whether cocoa flavanols could improve cognitive function in elderly patients with mild cognitive impairment (MCI), Desideri and colleagues assessed 90 elderly patients with MCI who were randomized to drink varying levels of a dairy-based cocoa containing flavanols per day for 8 weeks: 990 mg (high), 520 mg (intermediate), or 45 mg (low).
The researchers found that scores on the Mini Mental State Examination didn't change significantly in any of the groups ( P=0.13), a finding that was likely due to the low sensitivity of the test to detect small changes at the upper end of cognitive performance over time, they wrote.
There were, however, changes in the time required to complete Trail Making Tests A and B, with significantly greater improvements for those on high or intermediate doses of flavonols compared with those who had a low intake (P<0.05):
- High: -14.3 seconds for A, -29.2 seconds for B
- Intermediate: -8.8 seconds for A, -22.8 seconds for B
- Low: +1.1 second for A, +3.8 seconds for B
Scores on the verbal fluency test improved significantly for all groups, but, improvements were significantly greater for those who had a high versus low intake (P<0.05):
- High: +8.0 words per 60 seconds
- Intermediate: +5.1 words per 60 seconds
- Low: +1.2 words per 60 seconds
Also, the composite cognitive z-score significantly changed over the study period for the high and intermediate intake groups (P
Desideri and colleagues also observed improvements in several metabolic parameters, including blood pressure and insulin resistance, for those on high and intermediate doses of cocoa flavanols.
For blood pressure, the high flavanol group saw mean reductions of 10 mm Hg for systolic and 4.8 mm Hg for diastolic (P0.0001) while the intermediate group saw a mean drop of 8.2 mm Hg for systolic and 3.4 mm Hg for diastolic pressures. here were no significant changes for those taking a low dose of flavanols.
Plasma glucose fell a mean 0.6 mmol/L for those in the highest group and by 0.5 mmol/L for those on the mid-level dose (P0.0001) with no differences for low intake, and both the high and intermediate groups also had significant reductions inhomeostasis model assessment–insulin resistance (HOMA-IR) scores (-1.7 and -0.9 points, respectively).
Changes in HOMA-IR were found to be the main determinant of changes in cognitive function, explaining about 40% of composite z-score variability through the study period, the researchers reported (P<0.0001).
Thus the effect on cognition appears to be mediated in part by improvement in insulin sensitivity, the researchers wrote.
They noted that there were no changes in cholesterol or triglycerides in any of the groups.
The study was limited because its short time-frame didn't allow for conclusions about the extent of cognitive benefits and their duration. Nor can it establish whether the observed benefits are a consequence of the cocoa itself or a secondary effect related to general improvements in cardiovascular function or health. Also, participants were in good health overall and without known cardiovascular disease, so the population may be representative of all subjects with MCI.
Still, the researchers concluded that the data "are suggestive of a possible clinical benefit derived from the regular dietary inclusion of cocoa flavanol-containing foods in subjects with MCI."
The study was supported by a grant from Mars, Inc., which supplied the standardized powdered cocoa drinks used in the study. A co-author is an employee of Mars, Inc.
Reference: Desideri G, et al "Benefits in cognitive function, blood pressure, and insulin resistance through cocoa flavanol consumption in elderly subjects with mild cognitive impairment" Hypertension 2012.