Voice from the gut microbes
This is the news that we all have been waiting for. Chocolate is good for you, and dark chocolate is even better. In fact, the darker the better. In today’s post we are going to talk about microbes and chocolate, an unbeatable combination. It is well established that chocolate positively alters our mood but until recently, we didn’t know the exact mechanisms behind this phenomenon.
Being in a good mood is in fact more important than it may seem. Mood disorders include some serious conditions, such as “ongoing feelings of sadness, helplessness, hopelessness, and irritability” which can potentially lead to chronic physical and emotional health problems. Interestingly, the drugs prescribed to treat these disorders are not always sufficiently effective. This problem sparked a series of studies in nutrition and microbiome research aimed at better understanding of the reasons for mood swings and potential lines of treatment. More specifically, a group of Korean researchers have worked to find out exactly why our mood improves after eating chocolate (Shin et al., 2021). To do this, they put a special emphasis on the gut-brain axis of this correlation, meaning that they studied how chocolate affects our gut microbiome and how the gut microbiome consequently influences our mood. Sounds interesting but complicated? Well, this is what science is all about! Our job at Pretty Light Science is to keep it interesting while making it easier to understand. Let’s dive in.
The authors used three sample groups in their three week long study. The first group (DC85) consumed 30 grams of 85% chocolate per day (30g/p), the second group (DC70) consumed 30g/p of 70% chocolate, and the third group (control) didn’t consume any chocolate.
The researchers observed that consumption of 85% chocolate had a more significant positive effect on the mood than 70% chocolate so they focused more closely on comparing the DC85 group with the control. The results clearly indicated that diversity of microbes in the gut of the DC85 group was significantly higher compared to the control group.
In addition to increasing the overall diversity of the gut microbiome, 85% dark chocolate also had a significant effect on gut microbiota composition - i.e. which microbes were present. More specifically, it promoted “good bacteria” (those associated with positive mood scores) and inhibited “bad bacteria” (those associated with mood disorders). For example, Shin’s team observed lower concentrations of Faecalibacterium prausnitzii in the DC85 study group. F. prausnitzii is a bacterium that was reported to be negatively correlated with mood (the higher the abundance of F. prausnitzii, the worse the mood). They have also observed higher concentrations of bacteria from the genus Blautia, which were previously shown to be more abundant in healthy controls compared to patients with various psychiatric disorders (Huang et al., 2018; Luna et al., 2017). An important thing to keep in mind is that these correlations do not mean that F. prausnitzii and Blautia spp are always “bad” and “good” bacteria, respectively. For example, several studies demonstrated that F. prausnitzii plays an important role in maintaining gut physiology and it is now considered as a new generation probiotic (Lopez-Siles et al., 2017). This means that further research is needed to more precisely decipher the role of F. prausnitzii and other gut bacteria in influencing our health.
Next, let’s address an obvious question. Why is it important that dark chocolate may increase microbial diversity in the gut? Previous studies have demonstrated that composition of the microbial community in the gut may be a marker of the overall health status (Huang et al., 2018). Some serious diseases such as inflammatory bowel disease, major depressive disorder, and anxiety disorder may be -at least partially- caused by reduced bacterial diversity (Luna et al., 2017; Wong et al., 2016). Additionally, a diverse gut microbiome has been associated with higher levels of positive emotions and lower levels of loneliness (Serra et al., 2016; Filosa et al., 2018). These examples suggest that if dark chocolate consumption increases bacterial diversity in the gut, it may in turn have a major impact on our physical and emotional well-being. However, researchers still have a lot of work to do to understand the exact mechanisms behind these correlations.
Take Home message
In summary, Shin and his colleagues investigated potential links between dark chocolate consumption, microbial diversity in the gut, and finally human physical and emotional states. The results of this study are encouraging for dark chocolate enthusiasts. They suggest that eating a bit of dark chocolate every day has a positive effect on our mood by increasing microbial diversity in the gut and by promoting mood improving microbes.
References:
Shin, J.H., Kim, C.S., Cha, L., Kim, S., Lee, S., Chae, S., Chun, W.Y. and 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, p.108854. https://doi.org/10.1016/j.jnutbio.2021.108854.
Huang, Y., Shi, X., Li, Z., Shen, Y., Shi, X., Wang, L., Li, G., Yuan, Y., Wang, J., Zhang, Y. and Zhao, L., 2018. Possible association of Firmicutes in the gut microbiota of patients with major depressive disorder. Neuropsychiatric disease and treatment, 14, p.3329. https://doi.org/10.2147/NDT.S188340.
Luna, R.A., Oezguen, N., Balderas, M., Venkatachalam, A., Runge, J.K., Versalovic, J., Veenstra-VanderWeele, J., Anderson, G.M., Savidge, T. and Williams, K.C., 2017. Distinct microbiome-neuroimmune signatures correlate with functional abdominal pain in children with autism spectrum disorder. Cellular and molecular gastroenterology and hepatology, 3(2), pp.218-230. https://doi.org/10.1016/j.jcmgh.2016.11.008.
Wong, M.L., Inserra, A., Lewis, M.D., Mastronardi, C.A., Leong, L., Choo, J., Kentish, S., Xie, P., Morrison, M., Wesselingh, S.L. and Rogers, G.B., 2016. Inflammasome signaling affects anxiety-and depressive-like behavior and gut microbiome composition. Molecular psychiatry, 21(6), pp.797-805. https://doi.org/10.1038/mp.2016.46
Serra, D., Almeida, L.M. and Dinis, T.C., 2018. Dietary polyphenols: A novel strategy to modulate microbiota-gut-brain axis. Trends in food science & technology, 78, pp.224-233. https://doi.org/10.1016/j.tifs.2018.06.007.
Filosa, S., Di Meo, F. and Crispi, S., 2018. Polyphenols-gut microbiota interplay and brain neuromodulation. Neural Regeneration Research, 13(12), p.2055. https://doi.org/10.4103/1673-5374.241429.
Lopez-Siles, M., Duncan, S.H., Garcia-Gil, L.J. and Martinez-Medina, M., 2017. Faecalibacterium prausnitzii: from microbiology to diagnostics and prognostics. The ISME journal, 11(4), pp.841-852. https://doi.org/10.1038/ismej.2016.176
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