Dark chocolate may alter gut microbiome, improve mood: RCT

By Stephen Daniells contact

- Last updated on GMT

© Mizina / Getty Images
© Mizina / Getty Images

Related tags: Cocoa, Chocolate, Gut microbiome, mood, stress management, Prebiotic

Consuming an 85% cocoa dark chocolate significantly altered the diversity of the gut microbiome and improved mood in a randomized controlled trial with healthy young adults.

Data published in the Journal of Nutritional Biochemistry​ indicated that 30 grams per day of the dark chocolate for three weeks led to significant elevations in levels of a gut microbe called Blautia obeum​, and levels of this bacterium were positively correlated with improved mood.

“It has consistently been reported that the microbiota of healthy controls are enriched in ​Blautia in comparison to those of patients with psychiatric disorders such as MDD, autism, and schizophrenia,” ​wrote researchers from Seoul National University, the Korea Food Research Institute, and Chungnam National University in South Korea.

“Moreover, pharmacological inhibition of inflammasome signaling in stressed animals increases ​Blautia spp. in a manner that is compatible with a rebalancing of the gut microbiota, indicating that ​Blautia could serve as a microbial target in the gut microbiota-brain axis in psychiatric disorders.”

Cocoa’s benefits

The study adds the growing body of science around the potential health benefits of cocoa. To date, most of this has revolved around potential cardiovascular benefits of the flavanols (also known as flavan-3-ols or catechins), and particularly the monomeric flavanol (-)epicatechin. Additional studies have reported potential benefits for skin health, and brain health. 

There are also reports in the literature that cocoa-rich chocolate can improve measures of stress. For example, a 2009 study published in the Journal of Proteome Research​ indicated that consuming 40 g of dark chocolate per day for two weeks led to reductions in the stress hormone cortisol and catecholamines.

Barry Callebaut have also funded studies in this area​, with results of a 2013 randomized, double-blind study by scientists from the Swinburne University of Technology in Australia indicating that cocoa flavanols may keep you calmer and content without affecting cognitive performance (Journal of Psychopharmacology​, Vol. 27, pp. 451-458).

The new study from Korean suggests that dark chocolate may exert “prebiotic effects”,​ and that the potential benefits for mood and emotional state may be via the gut-brain axis.

Study details

Forty-eight healthy adults aged between 20 and 30 were recruited to participate in the Korean clinical trial. The participants were randomly assigned to one of three groups: A control group (no chocolate), a 70% cocoa chocolate group (30 grams per day), or an 85% cocoa chocolate group (30 grams per day) for three weeks. Mood states were assessed using the Positive and Negative Affect Schedule (PANAS).

The results showed that the negative mood scores were significantly reduced in the 85% cocoa group, but not the 70% group.

Gut microbiota analysis revealed that, compared to the control group, the 85% cocoa group displayed significant elevations in levels of Blautia obeum,​ while levels of Faecalibacterium prausnitzii​ were decreased.

“To the best of our knowledge, this is the first study that provides evidence that dark chocolate consumption in everyday life influences physiological and psychological states,” ​wrote the researchers. “These results suggest that dark chocolate has prebiotic effects by restructuring the diversity and composition of the gut microbiome, which may in turn improve mood via the gut-brain axis.”


A recent review in the journal Gut Microbes​ asked if Blautia​ could be considered “a new functional genus with potential probiotic properties”​. Research into the genus, and isolation and characterization of the species and strains is limited, noted the reviewers.

“As a dominant genus of intestinal microbiota, ​Blautia plays certain roles in metabolic diseases, inflammatory diseases, and biotransformation. However, most of the properties of this genus are linked with its potential probiotic functions, and the causal relationship between ​Blautia abundance and diseases is not yet clear,” ​wrote the reviewers. “… Whether ​Blautia plays a direct regulatory role in diseases requires further intervention studies and more detailed evidence.”

Source: Journal of Nutritional Biochemistry
Published online ahead of print, doi: 10.1016/j.jnutbio.2021.108854
“Consumption of 85% cocoa dark chocolate improves mood in association with gut microbial changes in healthy adults: a randomized controlled trial”
Authors: J-H. Shin et al.

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