OBJECTIVES: Parkinson's disease (PD) is a progressive neurodegenerative disorder with no cure and rising global prevalence. Genetic, environmental, and dietary factors may influence risk. Dairy intake, may influence risk through gut microbiome changes and alpha-synuclein spread along the gut-brain axis, though epidemiological evidence is mixed. This meta-analysis examines the association between dairy consumption and PD risk in observational studies.
STUDY DESIGN: This study is a systematic review and meta-analysis of published literature.
METHODS: PubMed and EMBASE were searched for original, peer-reviewed observational studies examining dairy intake and PD risk. Pooled risk estimates were calculated using fixed- or random-effects models depending on heterogeneity (Ithreshold: 50 %). Subgroup analyses by dairy type and sex were conducted. This study adhered to PRISMA guidelines. 2
RESULTS: Nine studies (eight cohort, one case-control) comprising diverse populations from the U.S., Europe, and Asia were included. A total of 15 results from 9 observational studies were analyzed. The combined cohort studies encompassed 634,327 participants with 4285 incident PD cases, while the case-control studies included 617 individuals (368 controls and 249 PD cases). High total dairy intake was significantly associated with increased PD risk (RR = 1.211; 95 % CI: 1.071-1.37; p = 0.002), with a stronger effect in males (RR = 1.282) than females (RR = 1.019). Milk consumption was also associated with increased PD risk (RR = 1.13; 95 % CI: 1.079-1.20; p < 0.001), with consistent sex-specific results. No significant associations were found for yogurt/fermented milk, cheese, butter, or ice cream.
CONCLUSIONS: Higher consumption of total dairy and plain milk is associated with an increased risk of developing PD. Further studies involving diverse populations and ethnicities should explore this association, stratified by genetic and sporadic forms of PD.
