New research suggests the makeup of gut bacteria could signal a person’s risk of developing Parkinson’s disease years before the first tremor shows up. Scientists compared stool samples from people diagnosed with Parkinson’s, those who carry a high-risk gene variant but have no symptoms, and healthy controls to look for consistent microbial differences. The study ties diet and geography into the picture and raises the possibility of detecting risk early, though it cannot yet prove cause and effect.
A team led by researchers at University College London analyzed microbes in fecal samples from three groups: 271 people with Parkinson’s, 43 people carrying a GBA1 variant linked to much higher risk who did not have symptoms, and 150 healthy controls. The design was observational, so the scientists could map associations but not yet confirm that bacterial shifts trigger the disease. Still, the sample mix allowed them to look for patterns that appear before classic motor signs arise.
The core finding was striking: more than a quarter of gut microbes were present at different levels in people with Parkinson’s compared with healthy individuals. People who carried the GBA1 variant but showed no symptoms already had microbial changes that looked like an intermediate stage between healthy and diagnosable Parkinson’s. That intermediate pattern hints that shifts in the gut could be an early signal, appearing before clinical symptoms become obvious.
The team also checked whether diet mattered. Participants who reported eating a more diverse and balanced diet were less likely to show the microbiome profile linked with higher Parkinson’s risk. That suggests lifestyle could influence those bacterial patterns, though diet is only one piece of a larger puzzle that includes genetics and other exposures. The work does not claim diet prevents the disease, but it points to a modifiable factor worth studying further.
The researchers replicated the main signals in a much broader sample spanning the U.K., Korea and Turkey, with more than 1,400 people overall, indicating the microbial differences are not limited to one culture or eating pattern. Publication in Nature Medicine gave the findings wide visibility and a signal that the science community is taking these signals seriously. Still, population-level differences in microbiomes remain a potential confounder for future work.
“Parkinson’s disease is a major cause of disability worldwide, and the fastest growing neurodegenerative disease in terms of prevalence and mortality,” lead author professor Anthony Schapira of the UCL Queen Square Institute of Neurology said in the release. “There is an urgent need to develop treatments that can stop or slow the disease’s progression.”
Clinicians note that gastrointestinal signs have long been tied to Parkinson’s biology. Patients with Parkinson’s are known to have significant gut abnormalities, and severe constipation can precede tremors and movement symptoms by several years. “There has long been a theory about the gut-brain axis and whether or not the pathology for Parkinson’s starts in the gut decades before stereotypical features are noted,” Murray, who was not involved in the research, told Fox News Digital.
The study lays groundwork for tests that could identify people at risk much earlier, opening a window to trial preventive strategies. The researchers and outside experts caution that not everyone with an at-risk microbiome will develop Parkinson’s, because genes and environmental exposures also shape outcomes. That uncertainty means microbiome screening would need to be combined with other markers to produce reliable risk estimates.
“With an aging population that is living longer, the prevalence of Parkinson’s is increasing significantly, which underscores the importance of studies like this that attempt to prevent this debilitating neurodegenerative disease,” Murray added. The investigators acknowledged observational limits but emphasized that consistent microbial signals across countries strengthen the case for more focused trials.
Experts also point out variability within Parkinson’s itself. “In general, people with GBA mutations tend to have Parkinson’s symptoms evolve in a way that is more consistent with a gut-first presentation,” Ellenbogen, who also was not involved in the study, told Fox News Digital. He added that some patients follow a different path: “In fact, many of these people don’t develop the symptoms of constipation and REM behavior disorder until later in their disease course,” Ellenbogen said. “These people may actually have a form of Parkinson’s that starts in the brain.”
Limitations noted by the team include the observational design and the fact that microbiome differences alone cannot predict individual outcomes with certainty. Other genetic and environmental factors could determine who ultimately develops Parkinson’s despite similar gut signatures. The study was funded by Parkinson’s research groups and medical research councils, and the authors call for longitudinal trials to test whether altering the microbiome can change risk or disease trajectory.
