Most of us think of Alzheimer's disease as something that begins in the brain. But what if part of the story starts much lower down, in the trillions of bacteria quietly living in your gut?
- Some gut bacteria make a compound called imidazole propionate (ImP) when they break down histidine, an amino acid found in protein-rich foods.
- In nearly 1,200 healthy adults, people with the highest ImP levels showed lower thinking scores and faster cognitive decline over time.
- About 43% of participants carried a gene variant linked to much higher ImP levels in the blood.
- In mice, ImP increased the build-up of amyloid and tau, the protein clumps seen in Alzheimer's disease.
- Researchers do not advise cutting out protein. A fibre-rich, less processed diet that supports a healthy gut is the sensible step for now.
Early evidence says yes, a molecule made by gut bacteria may raise Alzheimer's risk. A 2026 study from the University of Wisconsin–Madison, published in Nature Communications, found that adults with higher blood levels of imidazole propionate (ImP) had poorer memory and thinking scores, declined faster over the years, and showed more biological signs of Alzheimer's-related brain changes. The study does not prove that ImP causes Alzheimer's in people, but genetic and animal data point in that direction. That makes ImP a promising new target for prevention, and one more reason to look after your gut.
What is imidazole propionate?
Your gut microbiome is a large community of bacteria that helps digest food, trains your immune system and produces many compounds that travel through your blood. ImP is one of them. Certain bacteria make it while drawing energy from histidine, an essential amino acid present in foods such as dal, eggs, dairy, meat and nuts.
ImP is not new to scientists. Earlier research had already linked it to type 2 diabetes and coronary artery disease. European research published in 2020 also tied higher ImP levels to less healthy eating patterns and a less diverse gut bacterial community. The new Wisconsin work is among the first to connect it clearly to brain health.
What the Wisconsin study found
The research team, led by Professors Barbara Bendlin and Federico Rey, measured ImP in the blood of 1,196 adults with an average age of about 61. None of them had memory problems when they joined the Wisconsin Registry for Alzheimer's Prevention and the Wisconsin Alzheimer's Disease Research Center studies.
People with higher ImP levels scored lower on thinking tests, even after the researchers accounted for age, sex, body weight and the well-known Alzheimer's risk gene APOE4. Because many volunteers took the same tests over several years, the team could also track change over time. Those in the highest ImP group declined noticeably faster than those in the lowest group. Higher ImP also went hand in hand with markers of dementia-related protein build-up and nerve damage.
Interestingly, lifestyle risk factors such as diabetes, high blood pressure and inactivity explained only a small part of this link. ImP appeared to act largely on its own.
Clues from mice and genes
To test cause and effect, the team gave ImP to mice over a long period. The animals developed more amyloid and tau clumps, the two hallmark proteins of Alzheimer's. In lab tests, ImP also weakened the protective barrier of blood vessels in the brain.
The researchers also found a genetic variation, carried by about 43% of the study group, linked to much higher ImP in the blood. They believe it may affect how well the kidneys clear ImP from the body. The same gene region was linked to Alzheimer's risk, which strengthens the case that ImP plays a real role.
Should you stop eating protein?
No. Histidine is essential, and you need it for growth, tissue repair and making blood cells. As Professor Bendlin explained, the answer is not as simple as telling people to stop eating eggs. She added that improving your diet in general would probably help.
The bigger hope is a future medicine. Bendlin compares it to cholesterol: just as statins lower heart risk in people with high cholesterol, a drug that lowers ImP could one day reduce Alzheimer's risk and slow decline for many people. That work is still at an early stage.
Simple ways to support your gut and brain today
While science works on targeted treatments, the everyday advice is familiar and well supported. A varied, plant-rich diet feeds a wider range of helpful gut bacteria, which may leave less room for the less helpful ones.
- Eat more fibre from whole grains and millets such as ragi, jowar and bajra.
- Include dals, beans and chickpeas several times a week.
- Aim for a wide mix of vegetables, fruits, nuts and seeds.
- Add homemade curd or other traditional fermented foods.
- Cut back on ultra-processed snacks, sugary drinks and refined flour.
Small swaps add up. If you reach for a packet of fried chips in the evening, a baked millet option keeps the crunch while adding whole-grain fibre. Our iHTF Baked Ragi Chips are made with finger millet and baked, not fried, so they fit easily into a gut-friendly day.
The takeaway is hopeful. Alzheimer's risk is shaped by many factors, and this study adds the gut to that list. Caring for your gut through everyday food choices is one of the simplest things you can do for your long-term brain health.
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Frequently Asked Questions
1. What is imidazole propionate?
Imidazole propionate, or ImP, is a compound made by certain gut bacteria when they break down histidine, an amino acid found in protein-rich foods. It travels from the gut into the blood and has been linked in studies to type 2 diabetes, heart disease and, more recently, faster cognitive decline and Alzheimer's-related brain changes.
2. Can gut bacteria affect Alzheimer's risk?
Early research suggests they can. A 2026 University of Wisconsin–Madison study of nearly 1,200 healthy adults found that people with higher blood levels of the gut-made compound imidazole propionate had lower thinking scores and faster decline over time. Mouse experiments showed the compound increased amyloid and tau build-up in the brain.
3. Should I avoid protein-rich foods to lower imidazole propionate?
No. Histidine, the amino acid gut bacteria use to make imidazole propionate, is essential for health and found in many everyday foods such as dal, eggs, dairy and nuts. Researchers say cutting it out is not the answer. A generally healthier, fibre-rich and less processed diet is a more sensible step.
4. What foods support a healthy gut microbiome?
Foods rich in fibre and natural plant compounds feed helpful gut bacteria. These include whole grains and millets like ragi, lentils and beans, vegetables, fruits, nuts, seeds, and fermented foods such as homemade curd. Eating a wide variety of plants each week and limiting ultra-processed foods supports a more diverse gut community.
