Effects of theobromine, a caffeine‐like substance found in cocoa and chocolate, on mood and vigilance

Abstract

Like caffeine (CAF), theobromine (ThBr) is a methylxanthine found in foods such as cocoa and chocolate that might influence mood. ThBr crosses the blood‐brain barrier and binds to adenosine receptors, suggesting it might share CAF's beneficial effects on mood and vigilance. Therefore, we assessed the effect of ThBr doses commonly found in foods on mood and vigilance parameters sensitive to CAF. CAF was tested as a positive control. Twenty‐four males (age = 23 ± 3 y) completed six double‐blind trials during which they consumed experimental beverages, completed self‐report mood questionnaires, and completed a two hour visual vigilance task. Three experimental beverages (100 mg, 200 mg, and 400 mg ThBr) used a cocoa vehicle; three matched control beverages (0 mg ThBr, 400 mg ThBr, and 100 mg CAF) used a non‐cocoa carrier. Mean salivary [ThBr] exhibited appropriate dose‐dependent differences (400 mg trials > 200 mg trial > 100 mg trial > 0 mg trials, p < 0.05). At every dose tested, ThBr failed to consistently affect mood state or vigilance, but 100 mg CAF expectedly decreased lethargy/fatigue and increased vigor (p < 0.05). These findings indicate ThBr does not influence mood and vigilance when administered in nutritionally‐relevant doses, despite sharing many of CAF's characteristics. Further research is needed to better understand the behavioral effects of cocoa and dark chocolate.Funded by The Hershey Company.