Researchers have found a compelling link between soft drink consumption andmajor depressive disorder(MDD), especially in women. This study, published inJAMA Psychiatry, analyzed data from the Marburg-Münster Affective Cohort Study (MACS), involving 932 adults aged 18-65, including 405 diagnosed with MDD and 527 healthy controls. Soft drinks, popular especially among children and teens, are loaded with simple sugars like glucose and fructose, spikingblood sugarlevels. Excess sugar that the intestine can’t absorb fuels the growth of harmfulgut bacteria, which cause inflammation and weaken the gut’s protective barrier. This triggers systemic andbrain inflammationlinked toanxietyand learning issues. Meanwhile, diets promoting anti-inflammatory short-chain fatty acids (SCFAs) from beneficial bacteria supportgut healthand reduce inflammation, counteracting these negative effects of sugary drinks. The researchers used multivariable regression and analysis of variance (ANOVA) to explore associations between soft drink intake and depression diagnosis and symptom severity. They also conducted mediation analyses to examine if specific gut bacteria—Eggerthella and Hungatella—were involved. Soft drink consumption was self-reported, and gut microbiome diversity was assessed from stool samples. Findings revealed that each additional soft drink increased the odds of depression by 8%. Notably, women who consumed more soft drinks had nearly 16% higher odds of depression and greater symptom severity, while no such association was seen in men. Depressed individuals showed higher body mass indexes (BMI), but adjusting for BMI and antidepressant use did not alter the findings. Women with depression also exhibited altered gut microbiomes, with elevated levels of Eggerthella, a bacterium linked to inflammation and mood regulation. Mediation analysis indicated that this bacterium partly explained the relationship between soft drink intake and depression. The authors caution that, as an observational study, causality cannot be confirmed, and bi-directional effects may exist, with depressed women possibly consuming more soft drinks. Nevertheless, the data emphasize the urgent need for public health strategies to reduce soft drink consumption, especially among women, to potentially mitigate depression risk and improve gut health. Reference:Thanarajah, S. E., Ribeiro, A. H., Lee, J., et al. (2025). Soft Drink Consumption and Depression Mediated by Gut Microbiome Alterations. JAMA Psychiatry. doi: doi: 10.1001/jamapsychiatry.2025.2579. https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2839019