The study compared the effects of how the consumption of chocolates containing 85 per cent and 75 per cent of cocoa would affect a person's mood.
Subjects taking 85 per cent cocoa chocolate reported significant reduction in negative mood, but this was not seen in the group taking 70 per cent cocoa chocolate and the control group.
Findings were published on The Journal of Nutritional Biochemistry.
Conducted at Seoul National University, the RCT involved 48 healthy adults between 20 and 30 years old.
They were randomised to consume no chocolate at all, or 10 grams of 85 per cent cocoa chocolate (Weinrich 1895 Fine Dark Chocolate 85% Cocoa), or 70 per cent cocoa chocolate (Weinrich 1895 Fine Dark Chocolate 70% Cocoa) three times daily for three weeks.
The state of their mood was measured using the Positive and Negative Affect Schedule (PANAS), which comprises twenty adjectives that indicate positive or negative mood states.
The participants were asked to rate their feelings on a scale of one to five – which shows no or slight feeling or extremely intense feelings.
The researchers also conducted faecal 16S rRNA sequencing analysis in order to assess the association between the mood-altering effects of dark chocolate and the gut microbiota.
The health benefits of dark chocolate consumption, particularly the effects of polyphenols on mood, have been reported in several studies.
In human studies, the consumption of cocoa was shown to ameliorate negative emotions when stress and anxiety were experimentally induced.
However, the effects of cocoa remained debatable, since other studies reported no significant effects on mood.
“More importantly, the evidence regarding the emotional effects of dark chocolate intake in everyday life is limited, since most studies investigated its acute effects following experimentally induced psychological stress.
“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,” the researchers said.
Effects on mood
The research found that dark chocolate consumption had significant alterations on mood/feelings categorised as the ‘negative affect’ under PANAS.
Examples of the ‘negative affect’ include feelings of distress hostility, irritability, and nervousness.
In the group taking 85 per cent cocoa chocolate, their scores for negative affect had decreased significantly from 23.83 ±7.20 at baseline to 19.50±4.91 after the intervention was over.
A reduction in negative affect was also seen in the group taking 70 per cent cocoa chocolate – from 25.00 ± 8.17 to 22.69 ± 7.11.
An increase in negative affect was seen in the control group – up from 27.07± 6.92 to 28.93 ± 7.36.
However, dark chocolate consumption has no significant impact on mood/feelings categorised as the ‘positive affect’ – such as attentiveness, enthusiasm, alertness, and determination.
Scores of ‘positive affect’ maintained at 28.61 ±7.29 and 28.7 ± 5.13 before and after the intervention for the group which took 85 per cent cocoa chocolate.
“We found that dark chocolate consumption had no significant impact on positive affect. However, negative affect was significantly altered by dark chocolate consumption.
“In the present study, in agreement with previous findings, the DC85 [dark chocolate 85] group, in which participants consumed approximately 400 mg of polyphenols per day, exhibited remarkable effects on mood compared to the DC70 group, which was treated with 250 mg of polyphenols per day.
“Collectively, these results suggest that intake of dark chocolate with a higher cocoa content has a positive influence on negative emotional states,” the researchers said.
Effects on gut microbial
Gut microbial diversity was significantly higher in the dark chocolate 85 per cent group as compared to the control group.
For instance, Blautia obeum levels were significantly elevated, while Faecalibacterium prausnitzii levels were reduced in the group taking 85 per cent cocoa chocolate as compared to the control group.
From there, the researchers explained how Blautia obeum was linked to the negative affect scores.
First, they highlighted that the reduction in negative affect scores were negatively correlated with diversity and relative abundance of Blautia obeum.
“These results suggest that the mood-altering effect of 85 per cent dark chocolate consumption may be mediated by changes in the diversity and abundance of intestinal bacteria.
“These findings indicate that dark chocolate exerts prebiotic effects, as evidenced by its ability to restructure the diversity and abundance of intestinal bacteria; thus, it may improve negative emotional states via the gut-brain axis.”
Second, they cited existing studies which showed that the microbiota of healthy controls were enriched in Blautia, as compared to patients with psychiatric disorders such as MDD, autism, and schizophrenia.
Third, they explained that the mind-altering effects of cocoa may have originated from a variety of polyphenolic compounds present in dark chocolate.
They cited a large epidemiologic study which suggested that a high dietary intake of polyphenols was inversely associated with depressive symptoms.
A systematic review also concluded that dietary polyphenol and isoflavonoid intake was negatively associated with depressive symptoms.
No significant change in weight
There was no significant change in weight, skeletal muscle mass, body fat mass, BMI, and percent body fat in all groups after the intervention.
There was also no significant difference in the energy and macronutrient intake across the groups.
Source: The Journal of Nutritional Biochemistry
Consumption of 85% cocoa dark chocolate improves mood in association with gut microbial changes in healthy adults: a randomized controlled trial
Authors: Ji-Hee Shin et al