By Carrie Decker, ND
Founder and Medical Director, Blessed Thistle, Madison, WI
Dr. Decker reports no financial relationships relevant to this field of study.
Synopsis: Age-related decline in dentate gyrus activity and associated cognitive function is improved over a 3-month period by a diet including high amounts dietary flavanols from cocoa.
Source: Brickman AM, et al. Enhancing dentate gyrus function with dietary flavanols improves cognition in older adults. Nat Neurosci 2014 Oct 26; [Epub ahead of print].
Decline in functional integrity of the dentate gyrus, a hippocampal region, has been observationally seen with aging.1 However, beyond these correlations, direct association between cognitive decline, dentate gyrus function, and the effects of non-pharmacological interventions has not been demonstrated. This study was designed to assess the effects of a high flavanol dietary intervention and exercise on dentate gyrus function and cognitive performance.
A population of 41 healthy but sedentary 50- to 69-year-old subjects were randomly assigned to interventions of high dietary flavanols (900 mg cocoa flavanols and 138 mg of epicatechin per day) and active exercise, high dietary flavanols and no exercise, low dietary flavanols (10 mg cocoa flavanols and < 2 mg epicatechin per day) and active exercise, or low dietary flavanols and no exercise for a duration of 12 weeks. Active exercise consisted of 1-hour exercise sessions, including 40 minutes of aerobic activity four times a week. Exercise was performed at a target heart rate of 65-80% of each participant’s maximum heart rate for weeks 4 through 12 of the study, gradually ramping intensity in the weeks prior to this. There were no other dietary interventions, and individuals who used dietary supplements regularly were excluded from the study. Both participants and observers were blinded to intervention randomization.
Cerebral blood volume (CBV) measurement by functional magnetic resonance imaging is routinely used to measure changes in brain activity2 and is an established correlate of neuronal metabolism. The Benton Visual Retention Test (BVRT) has been shown to stimulate dentate gyrus function.3 However, in healthy individuals, a ceiling effect exists, and modifications were integrated to the test to eliminate this limitation. The primary outcomes of the modified BVRT and CBV were utilized to assess subjects both prior to and upon completion of the 12-week intervention period. At the end of the 12-week intervention, it was found that the high flavanol intervention had a significant effect on the modified BVRT performance, independent of exercise. Modified BVRT reaction times of the high flavanol group were 1997 ms compared with 2627 ms for the low flavanol group (P = 0.038). Preliminary data acquired from a general healthy population (ages 21-69 years) showed that the modified BVRT reaction time worsens with age, at approximately 220 ms per decade. The improvement seen with the high flavanol intervention is comparable to 2-3 decades of aging. No significant effect of the exercise intervention was seen in the modified BVRT performance. A significant increase in CBV in the dentate gyrus was also seen with the high flavanol intervention (P = 0.042), but the exercise intervention had no effect. Changes in the modified BVRT performance were shown to be correlated with CBV to the dentate gyrus.
In addition to positive benefits that chocolate consumption offers for cardiovascular health,4 this study offers further reason to consider chocolate in moderation as a part of a healthy diet. Flavanols are currently not a part of package labeling of chocolate; however, there are some flavanol-enriched products that do display this information on their label. Natural cocoa solids are high in flavanols. However, as flavanols are associated with bitterness, they may be processed out of chocolate products, particularly by the process of ditching.5 The amount of flavonoids in chocolate products range from the low end of approximately 26 mg per serving of chocolate syrup to 227 mg per serving of cocoa powder or baking chocolate.6 In general, flavanol content is correlated with percent cacao content of chocolate, so do consider this with your holiday snacking!
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- Brickman AM, et al. Hippocampal subregions differentially associate with standardized memory tests. Hippocampus 2011;21:923-928.
- Buijsse B, et al. Cocoa intake, blood pressure, and cardiovascular mortality: The Zutphen Elderly Study. Arch Intern Med 2006;166:411-417.
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- Miller KB, et al. Survey of commercially available chocolate- and cocoa-containing products in the United States. 2. Comparison of flavan-3-ol content with nonfat cocoa solids, total polyphenols, and percent cacao. J Agric Food Chem 2009;57:9169-9180.