Consumption of soft drinks is linked to obesity, diabetes, heart disease, stroke, and cancer. They are also associated with increased rates of depression. A recent study published examined how soft drinks were related to depression.
Study
The German study included a group of 405 patients diagnosed with major depressive disorder (MDD) and 527 healthy controls. The patients were drawn from the Marburg-Münster Affective Cohort, representing the general population. Both patients and controls were mostly female.
Multivariable regression and analysis of variance (ANOVA) models were used to identify associations between major depression, symptom severity, and soft drinks. Mediation analyses also explored the link between the gut microbes Eggerthella and Hungatella and soft drink consumption.
Results
Soft drink consumption predicted a higher rate of diagnosis of major depression. The odds of major depression were about 8% higher per unit increase in soft drink intake. People who drank more soft drinks were also more likely to have more severe depression.
These associations were driven by women participants, who had ~16% higher odds of major depression. In contrast, men failed to show any association.
Patients with depression had a higher mean body mass index (BMI) compared to controls. However, the observed pattern remained consistent even after adjusting for the BMI and for antidepressant use.
Interestingly, women who drank more soft drinks had a higher abundance of Eggerthella. An increase in Eggerthella abundance in female patients and controls partly mediated the association of depression with soft drink intake. About 4% and 5% of the association with depression diagnosis and severity, respectively, was caused by increased Eggerthella abundance.
BMI did not affect this association, which was not found in males. Moreover, the gut microbiome in women with depression was less diverse overall and showed less evenness of species distribution, with some species dominating the others. This was not seen with men.
This study is important in that it used a clinically diagnosed group of patients with depression, rather than including individuals who self-reported themselves as depressed. The authors noted that the observed effects were statistically small but may still be meaningful given how widely soft drinks are consumed. The effects attributable to soft drink consumption may be small but are easy to manipulate and wide-ranging in their reach.
These findings emphasize the need to educate consumers about the dangers of soft drinks to mental health. They also support policies restricting the marketing and availability of soft drinks since physical activity alone cannot compensate for soft drink intake.
Notably, moderate consumption, one or two soft drinks daily, has been associated with poorer health outcomes. These drinks should not be advertised to children, but support policies limiting soft drink availability. Taxation has reduced soft drink consumption and obesity rates in the UK. However, it has driven up the sales of artificially sweetened drinks, which were not separately analyzed in this study and may also warrant further research.
The reason for the predominantly female adverse effect of soft drinks remains unclear. Still, these findings highlight the need to interrupt the cycle of soft drink consumption and depression, especially since both impair normal metabolism. It is cautioned that the relationship might be bidirectional; people with depression could consume more soft drinks, so causality cannot be confirmed from this observational study.
Conclusion
Further interventions that alter the gut microbiome should also be tested. However, the authors emphasize that more research, including randomized trials, is needed to establish whether reducing soft drink intake can directly lower depression risk.
Source:
https://www.news-medical.net/news/20251010/Drinking-soft-drinks-may-fuel-depression-by-altering-gut-bacteria.aspx