Tuesday, 7 February 2017

Re: Cocoa Flavanol Intake Improves Cerebral Oxygenation without Improving Cognitive Function

  • Cocoa (Theobroma cacao, Malvaceae)
  • Exercise
  • Cognitive Function
  • Cerebral Oxygenation
Date: 01-31-2017HC# 011731-561

Decroix L, Tonoli C, Soares DD, Tagougui S, Heyman E, Meeusen R. Acute cocoa flavanol improves cerebral oxygenation without enhancing executive function at rest or after exercise. Appl Physiol Nutr Metab. 2016;41(12):1225-1232.

Because athletic performance depends partially on coordination, decision-making, and motor control, optimizing cognitive functioning during exercise is important. Exercise affects cognitive function depending on the type, intensity, and duration of the exercise. Researchers have increasingly focused on dietary constituents that can improve cognitive function; however, studies examining the acute effects of cognitive-enhancing nutritional supplements on exercise are limited. Reports show that acute cocoa (Theobroma cacao, Malvaceae) flavanol intake may improve cognitive function, cerebral blood flow in humans, and brain-derived neurotrophic factor (BDNF) levels in animals. BDNF is a biomarker associated with improved cognitive function induced by exercise. These authors conducted a randomized, double-blind, crossover, interventional study to investigate the effect of cocoa flavanol (CF) intake and exercise on cognitive function, cerebral hemodynamics, and BDNF levels. The authors hypothesized that acute CF intake would improve executive function (cognitive processes) by affecting cerebral hemodynamics and BDNF levels, and that CF could strengthen the beneficial effects of exercise on executive function.
Enrolled in the study were 12 well-trained men (mean age, 30 ± 3 years). [Note: The authors do not indicate where the study took place. However, the majority of the authors are from Belgium.] The study included 3 laboratory visits over 3 consecutive weeks, separated by 7-day washout periods. During visit 1, the subjects underwent a medical screening and completed an incremental cycle test to determine maximal oxygen uptake and peak power output. To prevent a possible learning effect, the subjects familiarized themselves with the cognitive task (CT) that would be used in the interventional trials by performing it 3 times.
During the next 2 intervention visits, the subjects reported to the laboratory after fasting for 4 hours. They refrained from intense exercise for 48 hours preceding the visit and abstained from caffeine and high-polyphenol foods for the preceding 24 hours. Both interventions started with a baseline 5-minute CT. The Stroop test was used as the CT; outcome measures were accuracy and reaction time (RT).
After completing the baseline test, the subjects consumed in a randomized manner either the high-CF Acticoa®(Barry Callebaut AG; Zurich, Switzerland) chocolate milk (903.75 mg flavanol) or a placebo (PL) of low-CF chocolate milk (15 mg flavanol). Along with the drink, the subjects ate a standardized, high-carbohydrate lunch to increase flavanol absorption. The subjects performed a second CT after 95 minutes, followed by a 5-minute warmup, and a 30-minute time trial on a cycle ergometer.
Subjects were instructed to complete a fixed amount of work on the cycle as fast as they could. Only the total workload completed was measured; time lapse, power output, heart rate, and pedal cadence were not recorded. The subjects performed a third CT approximately 5 minutes after the time trial. Blood samples were taken upon arrival and before and after the 30-minute time trial to analyze BDNF levels.
To assess cerebral blood flow, subjects underwent prefrontal near-infrared spectroscopy during the CTs and exercise to measure changes in oxygenated (HbO2), deoxygenated (HHb), and total hemoglobin (Hbtot).
The authors reported neutral RT on the Stroop task was faster after exercise than before exercise (P<0.05), but CF intake did not affect the results. For both groups, significant improvements in RT on the congruent and incongruent parts of the task were observed after exercise compared with pre-exercise testing (P=0.001 for both parts). No between-group differences were observed in the Stroop task results. A significantly greater increase in HbO2 was observed during the first part of the Stroop test in the CF group compared with the PL group (P=0.02). During the second part of the task, a similar, though not significant, increase in HbO2 was seen after CF intake. Both groups experienced significant increases in HbO2 (P=0.002), HHb (P<0.001), and Hbtot (P<0.001) after the time trial. Serum BDNF levels also increased after exercise in both groups (P<0.001).
"Contrary to our hypothesis," the authors write, "acute intake of CF did not result in improved cognitive performance (RT and accuracy on neutral, congruent, and incongruent stimuli and Stroop interference) compared with PL intake, neither at rest nor after exercise."
Addressing the study's limitations, the authors note that although a familiarization session was conducted 1 week before the study, some learning effect for the first part of the Stroop task could have existed. The authors also acknowledge "the fact that (left) prefrontal cortex hemodynamic and oxygenation recording is a regional measurement that may not be reflective of global cerebral changes." Because they did not measure hemodynamic changes at rest and the near-infrared spectroscopy measured relative and not absolute hemodynamic changes, the authors could not make any conclusions on the effect of CF on cerebral blood flow at rest.
In this study, acute CF intake increased cerebral oxygenation during the CT but did not impact cognitive performance compared with PL; CF intake did not affect serum BDNF levels. Exercise improved cognitive function and increased cerebral blood flow, oxygenation, and BDNF levels. Combining CF with exercise did not affect those benefits seen with exercise alone. 
Shari Henson