Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA169

Poster Communications

Effects of long-term dark chocolate intake on cognitive function in healthy young subjects

E. Sumiyoshi1, K. Matsuzaki1, N. Sugimoto3, Y. Tanabe1, T. Hara1, M. Katakura4, M. Miyamoto2, O. Shido1

1. Department of Environmental Physiology, Shimane university, Faculty of medicine, Izumo, Japan. 2. School of Nursing, Shimane university, Faculty of medicine, Izumo, Japan. 3. Department of Physiology, Kanazawa university, Graduate School of Medical Science, Kanazawa, Japan. 4. Department of Pharmaceutical Sciences, Josai University, Faculty of Pharmacy and Pharmaceutical Sciences, Sakado, Japan.


In our prior research in mice, orally-administered theobromine for about 1-month enhanced motor learning that was assessed using the three-lever task, suggesting improvement of cognitive function. However, it is not known how orally-ingested theobromine affects cerebral function in humans. There are various types of theobromine-enriched foods and beverages. Among them, chocolate is a remarkable commercially-available food. This study therefore investigated whether long-term intake of dark chocolate improves cognitive function in humans. Eighteen healthy young men (n=13) and women (n=5) (22 ± 3 (SD) years-old) were randomly divided into two groups; dark chocolate intake group (DC; n=10) and theobromine-free white chocolate intake group (WC; n=8, control). Subjects in each group took in dark or white chocolate every day for 30 ± 4 (SD) days. These chocolates were kindly provided by Dr. H. Inagaki, Morinaga & Co., Ltd. Before and after chocolate intake, cognitive function and prefrontal cortex function of all subjects were assessed using a modified Stroop color word test (modified SCWT) and Digit cancellation test (D-CAT). Blood samples were also taken for routine biochemical analysis. For modified SCWT, the subject's task is to look at a paper with color words written in a variety of random colors. The subject must read words (Words test) or name the ink colors (Colors test) as quickly and accurately as possible for 1 minute. The number of correct answers and errors were counted in both Words and Colors tests. The D-CAT was carried out with a standard method after finishing the modified SCWT. In addition, we continuously measured prefrontal cerebral blood flow (FCBF) with Near infrared spectroscopy (NIRS) and middle cerebral artery blood flow (MCABF) with an ultrasonic Doppler probe before and during the tests. In both groups, the same tests were repeated 3 weeks after the end of chocolate intake (Post). Body weight and body fat did not differ between the DC and WC groups through the intervention period (all, P>0.32). In the DC group, the number of correct answers in the Words test was significantly increased by chocolate intake (P=0.017). Furthermore, the high performance appeared to be persistent in the Post. Similar results were shown in the Colors test. White chocolate intake had no significant effects on both the Words tests and Colors tests (all, P>0.09). The FCBF and MCACBF during modified SCWT did not differ between the DC and WC groups (all, P>0.50). In D-CAT, similar improvement of performance was observed only in the DC group. There were no adverse changes in liver function and electrolyte values in both DC and WC groups. These results suggest that long-term dark chocolate intake may improve cognitive function in young subjects. Interestingly, this effect seemed to last for at least 3 weeks after the end chocolate intake. (COI: No)

Where applicable, experiments conform with Society ethical requirements