Regular consumption of soft drinks, which are sources of added sugars are linked to adverse outcomes of obesity, type 2 diabetes, cardiovascular disease, and cancer [1]. Observational studies have also connected the dots of frequent consumption of sugar sweetened beverages to poor mental outcomes, including depression [2].

A new multicenter analysis from the Marburg–Münster Affective Cohort examined whether soft drink consumption is associated with the diagnosis of major depressive disorder (MDD) and its symptom severity and tested whether gut-microbiome alterations specifically Eggerthella and Hungatella abundance is linked to MDD diagnosis and its severity. The study found statistically significant associations overall and stronger effects in women (See graphic for details) [1-4].

It is proposed that the sugars such as glucose and fructose from the soft drinks as well as the additives (e.g., preservatives and artificial sweeteners) in these drinks can disturb the balance between the protective bacteria and the inflammation-causing bacteria in the intestinal microbiome, in favour of the inflammation-causing bacteria. This leads to a reduction in the production of short-chain fatty acids by the protective bacteria. This may cause inflammatory reaction in the brain and result in depression [1,3]. Moreover, bacteria such as Eggerthella and Hungatella synthesize chemicals such as glutamate, butyrate, serotonin, and gamma amino butyric acid (GABA), which are key neurotransmitters influencing depression. A disruption in the synthesis of these neurotransmitters can result in mental health issues [4].

This study results have serious implications for public health policies. It is necessary to promote strategies to reduce the consumption of soft drinks, especially in the vulnerable population, so as to reduce the risk of MDD [2].