Casual Effects of Subtypes of Milk Consumption on Dementia and the Mediating Role of Gut Microbiota: A Mendelian Randomization Study

Dietary factors are increasingly recognized as modifiable contributors to dementia prevention, with dairy products receiving particular attention. However, the effects of dairy products on dementia risk remain controversial, mostly due to differences in milk types and dementia subtypes. In this Mendelian randomization study, we assessed the causal associations of 6 types of milk consumption with the risk of various dementia subtypes and further investigated the mediating effects of 30 gut microbial taxa. Our results showed that among all milk types, only soy milk was significantly associated with a reduced risk of frontotemporal dementia (FTD) (OR = 0.261, 95% CI: 0.108–0.635, <i>P</i> = 0.003). Mediation analysis revealed that this protective association was partially mediated by gut microbiota, particularly <i>Faecalibacterium prausnitzii</i>, which contributed for 14.75% of the total effect. These findings provide genetic evidence supporting the protective role of soy milk against FTD and emphasize the importance of dietary patterns and gut microbiota in developing dementia prevention strategies.