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| Date: 09-15-2015 | HC# 081531-528 |
Lamport DJ, Pal D, Moutsiana C, et al. The effect of flavanol-rich cocoa on cerebral perfusion in healthy older adults during conscious resting state: a placebo controlled, crossover, acute trial. Psychopharmacology (Berl). September 2015;232(17):3227-3234.
Flavonoids, particularly flavanols, have been studied for their effects on memory and learning. The consumption of cocoa (Theobroma cacao, Malvaceae), rich in flavanols, has been shown to improve cognitive function in healthy young and older adults. These effects may be mediated by increased cerebral blood flow (CBF), or blood supply to the brain, which stimulates neuronal function. These authors conducted a randomized, placebo-controlled, crossover trial to investigate regional perfusion in the human brain in the acute postprandial period after cocoa flavanol consumption.
The authors, from the University of Reading, Reading, United Kingdom, recruited 18 native, English-speaking, healthy adults aged 55 to 65 years (mean age, 61 years) with no neurological symptoms.
The study included 2 conditions (low flavanol [LF] and high flavanol [HF]) and 2 time points (baseline and 2 hours). On the first visit day, 9 subjects consumed an LF drink and 9 consumed an HF drink. After a 1-week washout period, the subjects consumed the alternate drink (visit day 2). The 330 mL drinks (Mars Incorporated; Hackettstown, New Jersey) were provided as dry, dairy-based cocoa beverage mixes. Total flavanol amounts were 494 mg in the HF drink and 23 mg in the LF drink. Epicatechins totaled 89 mg and 3 mg and catechins totaled 21 mg and 3 mg in the HF and LF drinks, respectively. Both drinks were matched in calories, macronutrients, micronutrients, theobromine, and caffeine, and also in flavor and appearance.
On each visit day, the subjects arrived at 8 am, after fasting the previous night and avoiding vigorous physical activity and polyphenol-rich foods for 24 hours. Upon arrival, they ate croissants and low-fat cream cheese. They then underwent a 12-minute functional magnetic resonance imaging scan including structural and arterial spin labeling (ASL) sequences to measure CBF before drinking the cocoa beverage. Two hours after cocoa consumption, a second 12-minute scan was conducted. During the 2 hours between scans, the subjects were allowed to consume only water.
The authors hypothesized that perfusion would increase between the 2 time points (baseline and 2 hours) only for those consuming the HF beverage. The authors observed significantly increased regional perfusion in subjects who consumed the HF drink compared with those who consumed the LF drink (P<0.05). More specifically, statistically significant increased perfusion was observed in the anterior cingulate cortex and regions of the parietal lobe 2 hours after consumption of the HF drink compared with the LF drink. According to the authors, these findings are consistent with the only published study1 of acute effects of a single cocoa flavanol dose on blood flow in the brain using ASL. In that study, increased global CBF was observed 2 hours after consumption of 516 mg cocoa flavanols in young adults. Results of the current study summarized here expand on those findings by demonstrating increased perfusion in specific brain regions in older adults.
As no task was performed in the current study, the authors found it difficult to associate the observed regions of increased perfusion and previously reported behavioral effects. Future studies should examine CBF and neuronal activation with behavioral cognitive measures after both long-term and acute consumption of cocoa flavanols.
The specific mechanisms responsible for regional perfusion are unknown; however, a beneficial effect of cocoa flavanols for peripheral and cerebral vascular function in humans is supported by a number of trials. In one study, consumption of flavanol-rich cocoa induced vasodilation through activation of the nitric oxide system,2 providing one plausible mechanism for vascular benefits. Also, cocoa flavanols have been linked to enhanced endothelial function; a recent meta-analysis reported a pooled estimate increase of 2% in flow-mediated dilation after cocoa consumption compared with placebo/control.3
Results of this study, which support the hypothesis that flavanol-rich cocoa beverages are associated with increased CBF within a 2-hour postprandial time frame, "add to the substantial body of literature demonstrating that flavanol consumption is beneficial for peripheral and cerebral vascular function and thus for maintaining, protecting and enhancing cardiovascular health," write the authors.
—Shari Henson
References
1Francis ST, Head K, Morris PG, Macdonald IA. The effect of flavanol-rich cocoa on the fMRI response to a cognitive task in healthy young people. J Cardiovasc Pharmacol. 2006;47(Suppl 2):S215-S220.
2Fisher ND, Hughes M, Gerhard-Herman M, Hollenberg NK. Flavanol-rich cocoa induces nitric-oxide-dependent vasodilation in healthy humans. J Hypertens. 2003;21(12):2281-2286.
3Petrone AB, Gaziano JM, Djoussé L. Effects of dark chocolate and cocoa products on endothelial function: a meta-analysis. Curr Nutr Rep. 2013;2(4):267-273.
