A single dose of cocoa flavanols improves cognitive performance during aerobic exercise

Consuming a single dose of cocoa rich in specific plant compounds can improve a person’s reaction time and decision-making skills during physically and mentally exhausting exercise. These cognitive benefits occur even though the individual still feels just as mentally drained, suggesting a subconscious boost to brain performance. The findings were published in the journal Psychopharmacology.

Hayato Tsukamoto, a researcher at the Faculty of Sport Sciences at Waseda University in Japan, led the investigation. His team wanted to understand how mental exhaustion affects physical performance and whether nutritional supplements could offer a protective effect. They focused their attention on a mental process known as executive function.

Executive function is a cognitive system that helps people manage their thoughts, direct their attention, and control their impulses. During sports like soccer or basketball, athletes constantly rely on this system to make rapid choices and block out distractions. Maintaining this mental sharpness is essential for high-level athletic performance.

When people use their executive function for an extended period, they experience a state of cognitive fatigue. This mental drain slows down their reaction speed and makes them more prone to errors. Physical exertion, like running or cycling, can add to this feeling of exhaustion and further degrade decision-making skills.

To combat this decline, the researchers looked to flavanols, which are naturally occurring chemical compounds found in the seeds of the cacao tree. These seeds are the primary ingredient used to make chocolate. Past research has shown that cocoa flavanols act as antioxidants in the human body.

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Antioxidants are substances that help protect cells from damage caused by harmful molecules. Previous tests revealed that cocoa flavanols could reduce mental fatigue when people were simply sitting at a desk. Tsukamoto and his colleagues wanted to see if these compounds could also protect decision-making skills when a person is exercising and thinking hard at the same time.

The researchers recruited eighteen healthy young men in their early twenties for the experiment. They utilized a placebo-controlled crossover design for the trial. This design means every participant completed the experiment twice on separate days to compare the true supplement against a dummy pill.

On one day, the men took a capsule containing five hundred milligrams of cocoa flavanols. On another day, they took a capsule with only fifty milligrams of the compounds to act as a placebo. The capsules were completely identical in appearance so the participants would not know which one they swallowed.

After taking the capsule, the men waited one hour for the plant compounds to reach peak levels in their bloodstream. They then completed a short, five-minute mental test to establish their baseline brain performance. This mental assessment is known as a color-word Stroop task.

The color-word task tests a person’s ability to process conflicting information and suppress incorrect impulses. For example, the word “red” might appear on a screen printed in blue ink. The participant must press a button corresponding to the ink color rather than the written word.

Following the baseline test, the men began a grueling fifty-minute exercise session. They rode a stationary bicycle at a moderate pace while simultaneously completing a continuous version of the color-word task. This combined effort was designed to induce a high level of cognitive fatigue.

Throughout the session, the researchers tracked how fast the men reacted and how well they handled the conflicting information. They also monitored heart rates and asked the men to rate their own feelings of mental exhaustion. Finally, the team drew blood to check for biological markers of cellular stress.

One hour after taking the capsules, but before the exercise began, the men showed distinct cognitive improvements. The high-dose cocoa capsule led to faster reaction times on the most confusing parts of the mental test compared to the low-dose capsule. The higher dose also improved their ability to filter out distracting information while resting.

As the fifty-minute cycling session dragged on, the cognitive benefits of the high-dose cocoa persisted. The men reacted more quickly to the conflicting word prompts while pedaling. Their overall ability to maintain focus and suppress incorrect impulses was superior when they had consumed the high-flavanol capsule.

Even a modest improvement in reaction time can be meaningful in competitive sports. The researchers noted that subtle differences in decision-making speed can dictate the outcome of major sporting events. A fraction of a second can determine whether a player successfully intercepts a pass or reacts to a referee’s call.

Despite the better performance, the high-dose cocoa did not change how the men actually felt. They reported the exact same levels of mental exhaustion and physical strain in both trials. The differences in their subjective feelings of fatigue were not statistically significant.

The blood tests also failed to show any changes in oxidative stress markers or a specific protein called brain-derived neurotrophic factor. This protein normally encourages the growth and health of brain cells. Because these blood markers remained unchanged, the exact biological process driving the improved reaction times remains unclear.

The researchers suspect that the flavanols might improve blood flow in the brain. Prior studies suggest that cocoa compounds can enhance the way blood vessels respond to increased demands for oxygen. When a person exercises and thinks hard simultaneously, the brain must divide its resources between the motor cortex and the prefrontal cortex.

The motor cortex controls physical movement, while the prefrontal cortex handles decision-making and focus. Improved blood vessel function from the flavanols might help deliver enough oxygen to both brain regions at once. This enhanced delivery could explain the faster reaction times even when the participants felt entirely exhausted.

The research team acknowledged a few specific limitations to their experiment. The study only included male participants, which limits how broadly the conclusions can be applied. Women experience natural hormonal fluctuations across the menstrual cycle that can influence cognitive function and reaction times.

Future research should examine the effects of cocoa flavanols on decision-making quality in female participants. Scientists need to account for the potential influences of changing estrogen levels. This will help determine if the cognitive benefits of cocoa apply equally to all athletes.

The researchers also noted that their blood tests only looked at a single marker of cellular damage. Measuring other biological markers might reveal exactly how cocoa flavanols protect the brain during physical stress. Assessing brain-specific markers rather than just circulating blood levels could provide more exact answers.

Scientists should also explore different dosages and timing strategies to find the optimal way to use cocoa supplements. The current study showed that a five-hundred-milligram dose is effective. Finding the ideal frequency of intake could offer a practical nutritional strategy for competitive athletes.

The study, “A single intake of flavanol-rich cocoa improves inhibitory executive process under cognitive fatigue during aerobic exercise in men: a randomized, double-blind, placebo-controlled crossover trial,” was authored by Hayato Tsukamoto, Sota Yoneya, Takahiro Koyama, Asuka Suzuki, I Wayan Yuuki, Kento Dora, and Takeshi Hashimoto.