A square of dark chocolate after a tough day. Chocolate and mood have long been associated in our social imaginary. But could there be more to it than comfort eating?
A recent randomized controlled trial published in The Journal of Nutritional Biochemistry suggests there might be. Not all chocolate is equal, and in this study, only very dark chocolate (85% cocoa) seemed to make a difference. Not just in taste or satisfaction, but in how people actually felt day to day. And the explanation might have less to do with pleasure, and more to do with what’s happening in the gut.
The research
The study followed 48 healthy young adults over three weeks. One group was asked to eat 30 grams of 85% cocoa chocolate daily — about three squares. Another ate the same amount of 70% cocoa chocolate, and a third group ate no chocolate at all.
At the end of three weeks, only the group eating 85% cocoa chocolate showed a statistically significant decrease in negative mood. They didn’t feel more euphoric or energized, positive affect stayed about the same, but they reported feeling less irritable, anxious, or upset. A subtle shift, but a meaningful one. Meanwhile, the 70% group saw no change in mood, despite eating the same amount of chocolate each day. This suggests that cocoa concentration might matter — and that the potential benefits don’t simply come from eating “some” dark chocolate, but from polyphenol-rich, minimally sweetened varieties.
The gut microbiome results backed this up. The 85% group experienced higher microbial diversity, often considered a sign of better gut health, along with changes in specific bacterial species. One microbe in particular, Blautia obeum, increased significantly and was inversely associated with negative mood. The more this microbe flourished, the less participants reported feeling distressed.
That said, it’s a small and short-term study. The participants were all in their 20s, and the chocolate doses were modest. It’s still unclear whether the changes would persist over time, or whether they would have any effect in people experiencing more severe stress or clinical depression. The study also didn’t pinpoint exactly which compounds in cocoa are responsible, though polyphenols, known for their antioxidant and anti-inflammatory properties, are the main suspects.
The takeaway
This small trial suggests that 85% cocoa dark chocolate, when eaten daily, may reduce negative mood and support gut health — possibly through changes in the microbiome. While it’s not a cure-all and more research is needed, the study adds to growing evidence that certain foods may influence how we feel, not just through nutrients, but through their effects on the gut-brain axis. The quality and concentration of what we eat may matter more than we think, even when it comes to chocolate.
Reference
Shin, J. H., Kim, C. S., Cha, J., Kim, S., Lee, S., Chae, S., … & Shin, D. M. (2022). Consumption of 85% cocoa dark chocolate improves mood in association with gut microbial changes in healthy adults: a randomized controlled trial. The Journal of nutritional biochemistry, 99, 108854. https://doi.org/10.1016/j.jnutbio.2021.108854
Lecturer at the Sociology Department, University of Barcelona