A molecule produced by gut bacteria has been linked to faster cognitive decline and markers of Alzheimer’s disease in a University of Wisconsin study. The research, published in Nature Communications, focused on imidazole propionate (ImP), a byproduct of the amino acid histidine. While the findings are significant, the study does not prove that lowering ImP protects memory, and no diet or probiotic has been proven to reduce its levels.
The study involved 1,196 adults without cognitive issues from Wisconsin research groups, including the Wisconsin Registry for Alzheimer’s Prevention. Participants with higher blood levels of ImP scored lower on cognitive tests and showed raised levels of pTau-217, a marker associated with Alzheimer’s. These markers are used in research to track brain changes but do not constitute a diagnosis.
Gut Bacteria and Cognitive Health: What’s the Link?
ImP is produced by certain gut bacteria, though these specific bacteria have not been definitively identified. In mouse models, ImP worsened the buildup of amyloid and tau proteins, which are hallmarks of Alzheimer’s. It also weakened the blood-brain barrier in lab experiments. However, the human data is observational, showing only an association, not a cause-and-effect relationship.
A common genetic variant, present in about 43% of participants of European ancestry, was linked to higher ImP levels and a slightly increased risk of Alzheimer’s. This variant shows the complexity of genetic influences on Alzheimer’s risk, but further research is needed to understand its full impact.
The research, led by UW–Madison professor Federico Rey, highlights that even low levels of certain gut bacteria can significantly impact health. “A microbe doesn’t have to be abundant to have an impact on the host,” Rey noted. This finding emphasizes the potential role of the gut microbiome in neurodegenerative diseases.
Diet and Probiotics: What Works?
Co-author Barbara Bendlin cautioned against simplistic dietary changes. Histidine, found in many protein-rich foods, is essential. “It’s not as easy as saying, ‘Stop eating eggs’ or ‘Don’t eat so much red meat,'” she said. The researchers stress that histidine is a necessary nutrient and cannot be eliminated from the diet without consequences.
No diet, probiotic, or supplement has been proven to lower ImP or prevent Alzheimer’s. The Alzheimer’s Association warns against untested supplements, advising consultation with a physician before use. “No one should take a supplement without first consulting a physician,” the group says, emphasizing the importance of medical guidance.
For those seeking actionable steps, managing blood pressure, diabetes, and cholesterol, treating hearing and vision loss, staying physically and socially active, and engaging in mental activities are supported by stronger evidence. The U.S. POINTER trial, published in JAMA in 2025, found that a structured program combining these elements produced a modest but statistically significant greater improvement in thinking skills than a self-guided program among older adults at risk of decline.
The next phase of ImP research will test whether lowering its levels can change outcomes in people, a process expected to take years. Until then, the study remains a scientific finding, not a prevention strategy. It was published in June 2026 and announced by the university in August, highlighting the importance of understanding the timeline of scientific discoveries.
The Role of Genetics and Future Treatments
Researchers hope to develop a drug that could lower ImP levels, similar to how statins reduce cholesterol. However, such a treatment does not currently exist.
Practical Steps for Brain Health
While the study on ImP is promising, it does not offer immediate prevention strategies. The Alzheimer’s Association and the 2024 Lancet Commission recommend addressing modifiable risk factors for dementia. The commission estimated that nearly half of dementia cases could be prevented or delayed by addressing 14 risk factors, including high blood pressure, diabetes, and physical inactivity.
For individuals noticing memory changes, consulting a clinician is advised. Newer blood tests and early Alzheimer’s treatments make timely evaluations more valuable. With an estimated 7.4 million Americans 65 and older living with Alzheimer’s dementia, early intervention is key.
