German study links soft drink intake to higher depression risk, with sex-specific findings
New research ties soda consumption to depressive symptoms and gut bacteria changes, notably among women, in an observational study from Germany.
A German study published in JAMA Psychiatry found that drinking soft drinks is associated with higher odds of developing major depressive disorder, with results that differ by sex. In a cohort of 405 people diagnosed with major depressive disorder and 527 without, researchers reported that higher soft drink intake predicted a depression diagnosis. The study also found that among women, there was an increased abundance of Eggerthella, a gut bacterium linked to depression, while Hungatella did not show the same association in this group. In men, the researchers did not observe a statistically significant link between soda consumption and depressive disorder.
Participants reported their mental health symptoms and soda intake, and stool samples were analyzed to characterize the gut microbiome. The authors suggested that sugar in soft drinks disrupts the gut bacterial community by decreasing beneficial microbes and increasing species associated with inflammation. They also cited data from animal studies showing that Eggerthella can reduce butyrate, a gut-protective short-chain fatty acid, and deplete tryptophan, a serotonin precursor. The researchers described the microbiome as a key mediator between diet and immune and brain function, a perspective echoed by outside experts who cautioned that observational data cannot prove causality.
"These findings underscore the role of diet in depression and highlight the gut microbiome as a key mediator," said Dr. Sharmili Edwin Thanarajah of University Hospital Frankfurt, who led the study. "The observed sex-specific effects suggest the need for tailored prevention and intervention strategies."
The study notes that about two-thirds of participants were women, raising questions about hormonal factors that might influence the relationship between sugar intake, gut bacteria and mood. The authors added that additional experimental work in humans and animals is needed to determine whether the observed associations reflect a causal link or result from unmeasured factors.
The research team highlighted Eggerthella as a focal bacterium in women with higher soda intake and depressive symptoms, while Hungatella did not show the same pattern in this group. They acknowledged that causal proof remains elusive and that future studies should explore whether changes in the gut microbiome mediate mood outcomes or simply accompany other risk factors associated with depression.
For readers seeking actionable guidance, experts suggested limiting sugar-sweetened beverages and prioritizing hydration with water. While popular probiotic beverages purport to improve gut health, some clinicians warn that they may contain added sugars or artificial sweeteners that can also affect the gut microbiome. "I don’t know that loading up on probiotic sodas is the answer, because many of those drinks are still high in sugar or artificial sweeteners that can disrupt the microbiome," said Dr. Anna K. Costakis, a psychiatry residency program director at Northwell Staten Island University Hospital.
In sum, the study adds to a growing body of evidence that diet influences mental health, potentially via the gut-brain axis, and it highlights the need for sex-specific research. Observational data cannot establish causation, but the findings may inform future preventive strategies and spur more rigorous trials that examine how dietary patterns affect mood disorders through gut microbiota.
