Dark chocolate, fatigue and brain function in middle-aged adults
What it found
In a four-week trial in healthy middle-aged adults, eating 72% dark chocolate reduced mental and physical fatigue compared with no chocolate.
The authors say this fatigue reduction may be linked to better executive function, memory and gray matter volume.
What they found
Studies in people
Fatigue reduction
The dark chocolate group had a bigger drop in physical and mental fatigue than the control group after four weeks. When physical and mental fatigue were looked at separately, neither one on its own showed a significant difference.
Physical role limits
The chocolate group improved more on role limitations due to physical functioning, based on the SF-36 questionnaire. No other SF-36 domains showed a significant difference between groups.
Brain structure
The study did not find a direct link between chocolate consumption and gray matter volume or fractional anisotropy. The authors suggest four weeks may be too short for structural brain changes.
Cognitive function
There was no direct relationship between the chocolate intervention and cognitive test performance. The path analysis linked fatigue reduction to better executive function and memory indirectly, through improved vitality and mental health.
Body mass index
Body mass index changed very little in both groups over the four weeks, with no significant difference between them.
What the authors conclude
“Our results suggest that dark chocolate may help reduce fatigue in individuals, leading to improvements in brain health and various cognitive functions as well as in quality of life.”
Also in their conclusions
- They suggest that dark chocolate may help reduce fatigue in individuals, leading to improvements in brain health and various cognitive functions as well as in quality of life.
- They note that fatigue may be a mediating factor between dark chocolate consumption and health outcomes.
- They advise that more participants from various countries and a longer intervention period might be required to address the study's limitations.
How it was done
Past results on dark chocolate and cognitive function have been inconsistent, which suggests other factors may sit between chocolate intake and cognition. The authors suspected fatigue might be one such factor.
They randomly assigned middle-aged adults aged 40 to 65 to eat five pieces of 72% dark chocolate a day for 28 days, or to make no changes and avoid chocolate. Questionnaires, cognitive tests and MRI scans were done at the start and end.
What it can’t tell you
- The trial lasted only four weeks, so it cannot show what longer-term chocolate eating might do.
- The sample was relatively small, and the authors note that dietary patterns could affect the results.
- The study was in healthy middle-aged Japanese adults, so the findings may not apply to other groups.
Who paid
- Conflicts
- Authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as potential conflicts of interest.
- Authors work at
- University of Tsukuba, Japan; Kyoto University, Japan; Kyoto Seika University, Japan
The paper
- Title
- Dark Chocolate Intake May Reduce Fatigue and Mediate Cognitive Function and Gray Matter Volume in Healthy Middle-Aged Adults
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Nemoto K, Kokubun K, Ogata Y, Koike Y, Arai T, Yamakawa Y (2022). Dark Chocolate Intake May Reduce Fatigue and Mediate Cognitive Function and Gray Matter Volume in Healthy Middle-Aged Adults. Behavioural neurology. doi:10.1155/2022/6021811Free full textPubMed 36561325DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error