A German multicentre study has highlighted a potential link between soft drink consumption and depression, particularly among women. Researchers reported that women who consumed more soft drinks were more likely to be diagnosed with major depressive disorder (MDD) and to experience more severe symptoms. Interestingly, this association did not appear in men, suggesting a possible gender-specific effect.
German Cohort Links Soft Drink Intake, Gut Microbiome, and Depression in Women
The study, conducted within the Marburg-Münster Affective Cohort between 2014 and 2018, analysed data from 405 individuals with MDD and 527 healthy controls aged 18 to 65. Participants self-reported their diets, underwent structured psychiatric interviews, and completed the Beck Depression Inventory to measure symptom severity. In addition, gut microbiome composition was studied through 16S rRNA sequencing, with models adjusted for education and recruitment site.
Among the findings, investigators noted that women with higher soft drink intake had reduced microbial diversity and a greater abundance of the gut bacterium Eggerthella. This bacterium partly mediated the relationship, accounting for roughly 3.8% of the association with MDD diagnosis and 5% of the effect on symptom severity. Although overall microbial diversity declined with greater soft drink consumption, diversity itself was not directly linked to depression outcomes. The associations remained significant even after accounting for body mass index.
Frankfurt Team Highlights Complex Mediators, Warns Against Overinterpretation
Lead author Dr. Sharmili Edwin Thanarajah from the University Hospital Frankfurt emphasized that mediators in complex systems should not be evaluated by effect size alone, but rather by their functional role within biological interactions. Additional sensitivity analyses—such as excluding participants with eating disorders and adjusting for calorie intake—further supported the findings.
However, researchers cautioned that the cross-sectional design prevents conclusions about causality. It is possible that depression may drive increased soft drink consumption rather than the reverse. Dietary data were based on recall and did not distinguish between sugar-sweetened and artificially sweetened drinks, further limiting interpretation.
Summary:
A German cohort study found higher soft drink intake linked to major depressive disorder and worse symptoms in women, but not men. Gut microbiome changes, including increased Eggerthella, partly explained the link. Researchers cautioned causality couldn’t be proven due to study limits, recall bias, and lack of sweetener differentiation.
