Researchers discovered that a single serving of dark chocolate milk improved sprint times and power output in young adults, suggesting its potential as a natural ergogenic aid, though benefits remain modest and context-dependent.
Study: Effects of Dark Chocolate on Physiological and Anaerobic Performance Among Healthy Female and Male Adults. Image Credit: xpixel / Shutterstock
In a recent study published in the journal Nutrients, researchers examined the effects of dark chocolate milk (DC milk) consumption on anaerobic sprint performance in healthy adults. DC milk contains biologically active compounds, such as catechins, epicatechin, theobromine, and procyanidins, that may support cardiovascular health.
Studies have reported that consuming dark chocolate products with high cocoa content may improve performance in endurance sports. Moreover, reduced mental and physical fatigue has been observed in dark chocolate consumers, leading to higher executive function. However, no study has examined the impact of dark chocolate milk on anaerobic performance.
About the study
In the present study, researchers assessed whether DC milk influences metabolic processes and increases performance during an anaerobic sprint test. They recruited individuals aged 21–35 years, with no medication use, no musculoskeletal injuries within the last six months, who exercised thrice per week, performing ≥75 minutes of vigorous-intensity physical activity or ≥150 minutes of moderate-intensity physical activity per week.
Participants were randomized to receive DC milk or iso-caloric white chocolate (WC) milk as a flavonoid-free control. They completed two trial sessions (WC and DC) with a 7-day washout period between them. Participants were asked to maintain their usual diet and physical activity throughout the study to reflect real-world conditions. Females completed the first trial during their follicular phase of the menstrual cycle. Participants completed a physical activity readiness questionnaire before the test.
In addition, participants' body composition, height, weight, and heart rate (HR) were recorded. Subsequently, the DC group consumed 300 mL of DC milk, while the WC group consumed 300 mL of milk mixed with WC flavor. Participants rested for 1.5 hours after drinking their assigned beverage to allow for digestion. They completed a set of warmups 10 minutes before starting two sets of the running-based anaerobic sprint test (RAST).
RAST involved six 35-meter sprints with 10 seconds of passive recovery between sprints. Timing gates were used to measure the time to complete each sprint. The rate of perceived exertion (RPE) and HR were recorded before the test and after the second, fourth, and sixth sprints. A four-minute rest was allowed after the first set of RAST before continuing to the second set.
Fatigue index (FI) and power output were calculated. A t-test was performed to compare performance and physiological data between RAST sets. Analysis of variance (ANOVA) was performed to estimate the average power output, average sprint time, HR, and RPE for each set and trial and between genders.
Findings
The study recruited 20 adults, with an average age of 25.07 years and a body mass index (BMI) of 22.85 kg/m². Significant differences were observed in FI during the first RAST and total effort time, average sprint time, mean power, and relative mean power during the second RAST between DC and WC trials. Specifically, mean power (p = 0.009) and relative mean power (p = 0.007) were significantly higher for DC milk compared with WC during the second RAST, as shown in paired t-test results. In addition, males and females showed significant trial differences in FI and resting HR, respectively, during the first RAST.
Further, males demonstrated greater improvements in mean power and relative mean power during the second RAST compared with females, highlighting a possible gender-specific response. A significant difference was observed in average sprint times across sprint sets and trials. There was an important difference in average sprint times between females during the first RAST in DC and WC trials, but not during the second RAST in WC and DC trials.
In contrast, no significant differences were observed between average sprint times for males in the first and second RASTs in DC and WC trials. Further, there were no significant between-trial differences in average power output per individual sprint set, even though the overall second RAST mean power improved for DC milk. Similarly, no significant differences were observed in average HRs or RPEs between the first and second RASTs in WC and DC trials.
Conclusions
The study findings showed that dark chocolate milk intake significantly improved total effort time and average sprint time in the second RAST. It also increased the mean and relative mean power output during the second RAST, particularly among male participants. There were no significant differences in average HR or RPE across sprint sets or trials. As such, the beverages' ability to further improve performance was likely negligible. Notably, FI was significantly different between trials in the first RAST, and resting HR was lower in females after DC milk intake, suggesting possible modulation of autonomic recovery.
Overall, the findings suggest that dark chocolate milk may modestly enhance anaerobic sprint performance, likely due to the combined effects of flavonoids and sucrose on blood flow and glycolytic energy supply. However, the authors noted that no physiological biomarkers such as nitric oxide (NO) were directly measured, so mechanistic explanations remain hypothetical.
Importantly, the authors cautioned that the improvements observed were statistically minor (around 0.5–1.5%) and may have limited practical significance for general exercisers, though such margins could be meaningful for competitive athletes.