Imidazole Propionate: The Gut Bacteria Molecule That Drives Heart Disease

A 2025 study in Nature identified a gut bacteria-derived molecule called imidazole propionate (ImP) as a direct driver of atherosclerosis, with elevated blood ImP showing up in early-stage disease before standard cardiovascular risk factors do (Mastrangelo et al., 2025). Follow-up work in the European Heart Journal showed that high ImP independently predicts heart attacks, strokes, and death in patients with established coronary artery disease, on top of cholesterol and inflammation markers (Halvorsen et al., 2025). Here is what ImP actually is, how your gut produces it, and the small set of evidence-backed moves that can keep your levels lower in 2026.

Key takeaways

• Imidazole propionate (ImP) is a small molecule that some gut bacteria make when they metabolize the dietary amino acid histidine, per the foundational Cell paper by Koh et al., 2018.
• In a landmark 2025 Nature paper, ImP drove plaque formation in atheroprone mice by binding the imidazoline-1 receptor (I1R) on immune cells, and blocking that receptor completely prevented the damage.
• ImP was elevated in two independent human cohorts with early atherosclerosis — the Spanish PESA cohort (~400 participants) and a larger international cohort (~1,800 participants) — even after controlling for LDL cholesterol and hsCRP (Gut Microbiota for Health summary).
• In US adults, the highest ImP tertile carried roughly 2× the risk of coronary heart disease vs the lowest, with red-meat-heavy and low-fiber diets pushing levels up.
• You cannot measure ImP at home today. The evidence-backed levers are dietary — more fiber and plant diversity, less ultra-processed food, mindful protein sources — plus the gut-microbiome basics that already matter.

What imidazole propionate actually is

Most “gut-microbiome metabolites” you read about (short-chain fatty acids, bile acids, indoles) are produced by your bacteria from things you ate. Imidazole propionate is the same idea, but the parent ingredient is the essential amino acid histidine found in every protein-containing food: meat, fish, eggs, dairy, legumes, nuts, and seeds.

Healthy gut bacteria mostly convert histidine into other metabolites. But certain bacterial species (including several Clostridium and Ruminococcus strains) possess the enzyme urocanate reductase, which shunts histidine down a side path that ends in ImP (Nature Communications, 2021). The bacteria themselves are fine. The problem is what ImP does once it crosses into your bloodstream.

The first inkling that ImP was bad news came in 2018. A group led by Fredrik Bäckhed at the University of Gothenburg found that people with type 2 diabetes had significantly higher blood ImP than people without it, and showed in cell and mouse experiments that ImP impairs insulin signalling through the mTORC1 pathway (Koh et al., Cell, 2018). Follow-up work added that ImP blunts the effect of metformin, the most-prescribed type-2 diabetes drug, making it a candidate explanation for why some people respond poorly to the medication.

For the better part of a decade, ImP looked like a diabetes story. The 2025 Nature paper redirected it into cardiology.

What the 2025 Nature paper actually showed

The study, Imidazole propionate is a driver and therapeutic target in atherosclerosis (Mastrangelo et al., Nature, 2025, vol. 645, pp. 254–261), was led by researchers at the Spanish National Centre for Cardiovascular Research (CNIC) in Madrid in collaboration with the University of Gothenburg, the Karolinska Institute, the University of Zurich, and Mount Sinai. The work was funded in part by a European Research Council Advanced Grant.

The team ran the analysis in three layers:

1. Human cohorts. They measured plasma ImP in two independent populations: the Spanish PESA (Progression of Early Subclinical Atherosclerosis) cohort and a larger international cardiometabolic cohort. People with early, subclinical atherosclerosis had significantly higher ImP than those without it. The association held after adjusting for age, sex, BMI, fasting glucose, blood pressure, LDL cholesterol, and high-sensitivity C-reactive protein (hsCRP), meaning ImP was carrying information traditional risk factors missed.
2. Mouse experiments. When the researchers gave ImP orally to mice prone to atherosclerosis, plaque area in the aorta increased, even without raising cholesterol. ImP was not just a passive marker. It was driving the disease.
3. Mechanism. ImP binds imidazoline-1 receptor (I1R / nischarin) on myeloid immune cells, activating the mTOR pathway and amplifying inflammatory signalling inside arterial-wall macrophages. When the team genetically deleted I1R in myeloid cells, or used an I1R blocker, ImP-driven plaque formation was abolished.

That is the rare research package: a human marker, a causal mouse model, a clean molecular mechanism, and a druggable target, all in one paper. Nature Reviews Cardiology called ImP “a potential biomarker of and therapeutic target for atherosclerosis” in a July 2025 commentary.

How the gut-heart axis fits the bigger picture

Cardiologists have known for over a decade that the gut microbiome talks to the cardiovascular system. The first big story was TMAO (trimethylamine N-oxide), a metabolite some gut bacteria produce from choline and L-carnitine in red meat and eggs; high TMAO was linked to atherosclerosis and major cardiovascular events. ImP now joins TMAO as a second well-characterized “gut-to-artery” metabolite, and the 2025 European Heart Journal paper found ImP added predictive value beyond TMAO in people with coronary artery disease.

Concretely, in patients with acute coronary syndromes and chronic coronary syndromes, high ImP independently predicted major adverse cardiovascular events (MACE) and mortality after adjustment for standard risk factors. That moves ImP from “interesting molecule” to “candidate risk marker your cardiologist may eventually order alongside LDL and hsCRP.”

The wider point is that the gut-heart axis is one of several lanes (like the gut-brain axis) by which your microbial community shapes organs that are not the gut. The mechanism is the same in all of them: bacteria turn what you eat into molecules, those molecules enter the blood, and they signal to receptors in distant tissues.

What raises your imidazole propionate

The current dietary evidence on ImP is consistent, if early:

• Higher histidine intake from red meat was associated with higher plasma ImP in a pooled US cohort analysis, particularly in people whose gut microbiome carried a high “ImP-producing species score” (14 bacterial species including Ruminococcus obeum, Clostridium clostridioforme, C. nexile, C. symbiosum, and Gordonibacter pamelaeae).
• An “unhealthy” Western-style dietary pattern — more processed meat, refined grains, sugar; less fiber and plant diversity — tracked with higher ImP across multiple cohorts.
• A low-fiber gut environment appears to be a permissive condition. Fiber feeds short-chain-fatty-acid-producing bacteria that crowd out and outcompete the histidine-shunting species. For the practical fiber targets, see our piece on fiber and stool consistency.
• Antibiotic exposure suppresses ImP transiently by knocking out the producing bacteria. That is useful as proof-of-mechanism, but obviously not a recommended intervention. For how the gut community rebuilds after a course, see antibiotics and gut microbiome recovery.
• Histidine itself is not the villain. Oral histidine alone produces relatively little ImP in healthy people; the bacterial enzyme has to be there for the conversion to happen (npj Biofilms and Microbiomes, 2024).

The honest read: ImP is a consequence of a specific gut-microbiome state plus a histidine-rich, low-fiber substrate. It is not about avoiding protein. It is about the microbial context that determines what your bacteria do with the protein you eat.

What this study does not prove

The ImP story is strong, but a few limits matter before you change anything:

• No clinical test. There is currently no consumer or routine clinical assay for plasma ImP. Even the most comprehensive consumer gut-microbiome tests on the market do not report it.
• Causation in mice, association in humans. ImP causes atherosclerosis in atheroprone mice. In humans, ImP is associated with disease severity and predicts outcomes, but the causal arrow has not been proven by a randomized trial that lowers ImP and shows fewer heart attacks.
• No approved therapy. I1R blockers exist for blood-pressure management (moxonidine, rilmenidine), but they are not approved or tested for atherosclerosis prevention. A targeted “ImP-lowering” drug does not exist yet.
• The mechanism is one of several. Heart disease has many drivers: LDL cholesterol, blood pressure, smoking, insulin resistance, inflammation, lipoprotein(a), and now metabolites like TMAO and ImP. None of them are the whole story.

What you can actually do in 2026

The practical playbook is not new. The 2025 ImP work sharpens why the standard “feed your microbes” advice is more than wellness folklore — it appears to literally change which bacterial metabolites end up in your bloodstream attacking your arteries.

1. Eat 25–35 g of fiber per day from diverse plant sources. Fiber-fermenting bacteria outcompete the histidine-shunting species responsible for ImP, and short-chain fatty acids they produce are independently protective for the gut barrier and the vascular endothelium.
2. Anchor your diet on the Mediterranean / plant-forward pattern. Vegetables, legumes, whole grains, nuts, olive oil, fish, and modest amounts of fermented dairy. Multiple cohorts link this pattern to lower ImP and lower cardiovascular events.
3. Be deliberate about red and processed meat. A small amount is fine. Daily steak, deli meat, and bacon is the dose that consistently associates with higher ImP and higher heart-disease risk.
4. Skip the supplement-aisle “ImP blockers.” They do not exist. Anything sold as one in 2026 is marketing on top of headlines, not science.
5. Mind diabetes risk specifically. If you have type 2 diabetes or prediabetes, the ImP story is doubly relevant: it impairs insulin signalling and drives atherosclerosis, so the Ozempic-era and metformin-era conversation about gut-metabolite biology is now substantially clinical, not theoretical.
6. Track the downstream signal. You cannot see ImP. You can see whether your overall gut community is in good shape — see how to improve gut health for the consolidated playbook.

What it means for daily stool tracking

ImP is a blood metabolite, not a stool feature. There is no “ImP color” or stool consistency that says “your bacteria are making too much of it.” But the upstream conditions that drive high ImP — a low-fiber, ultra-processed, low-diversity gut environment — also produce the everyday gut symptoms PoopCheck users notice first: more variable consistency, harder or pellet-like type-1/2 stools, more straining, more gas, and slower transit.

When someone overhauls their diet toward more fiber and more plant diversity, the stool readout usually moves before any clinical marker does. PoopCheck classifies each bowel movement from a photo and surfaces the trends over weeks, so if a Mediterranean-pattern shift is doing what the literature predicts, you see it in the daily log before it would ever show up on a lipid panel. The post-meal, post-fiber, post-change signal is the kind of pattern paper journals lose and apps catch.

FAQ

Is imidazole propionate something I should ask my doctor to test?

Not yet. There is no clinically validated plasma ImP assay available in most labs, and even where research labs measure it, no specific clinical threshold or treatment guideline exists. The 2025 Nature paper and follow-up European Heart Journal outcomes work are setting the stage for ImP to enter clinical risk stratification, but it is years from being a routine test.

Will eating more histidine give me higher ImP?

Probably not on its own. Healthy people who took oral histidine in a controlled 2024 npj Biofilms and Microbiomes study produced relatively little ImP — the rate-limiting factor is whether you carry the gut bacterial species with the urocanate reductase enzyme. The bigger driver is overall diet pattern (low fiber, high ultra-processed, high red meat), not histidine per gram.

Does this mean red meat is the new smoking?

No. Red meat is one input that, in the context of a low-fiber gut environment and certain bacterial species, can push ImP higher. Moderate red meat in a fiber-rich, plant-diverse diet is not the same exposure as daily processed meat in a low-fiber diet. The pooled US cohort analysis showed the histidine-ImP-heart-disease link was strongest in people with the high “ImP-producing species score” — context matters.

Can a probiotic lower my ImP?

There is no probiotic on the market today with human evidence for lowering ImP. The mechanism that would matter — outcompeting the histidine-shunting species — looks more like a prebiotic/fiber story than a single-strain probiotic story. For the broader category, see probiotics vs prebiotics.

How does ImP compare to TMAO?

TMAO and ImP are now the two best-characterised “gut-derived cardiovascular metabolites.” TMAO comes from choline and L-carnitine (red meat, eggs, energy drinks); ImP comes from histidine. The 2025 European Heart Journal paper found ImP added predictive value beyond TMAO in coronary-artery-disease patients, suggesting they capture different slices of microbial cardiovascular risk.

Does the new finding change anything for healthy people?

Indirectly, yes — it adds a mechanistic reason to take the standard gut-microbiome and Mediterranean-diet advice seriously. The everyday moves (fiber, plant diversity, less ultra-processed food) were already worth doing; the 2025 work shows one specific pathway by which they appear to protect your arteries.

The bottom line

The 2025 Nature paper on imidazole propionate is one of the cleanest demonstrations to date that a single gut-bacteria metabolite can directly drive heart disease — not just track with it. Combined with the European Heart Journal outcomes data, ImP now sits alongside TMAO as a real “gut-to-artery” link your cardiologist may eventually measure. There is no test or drug for the public yet, and there will not be one for some time. What the finding does is sharpen the case for the gut-microbiome basics that already had evidence behind them: fiber, plant diversity, less ultra-processed food, and a deliberate eye on red and processed meat. None of that is new advice. The new thing is the mechanism by which your daily plate appears to translate into either inflammation in your arteries or not — and what your stool tells you, day to day, about which side of that line your gut community is on.

Sources

1. Mastrangelo, A. et al. Imidazole propionate is a driver and therapeutic target in atherosclerosis. Nature, vol. 645, pp. 254–261, 2025. https://www.nature.com/articles/s41586-025-09263-w
2. Halvorsen, B. et al. Gut microbiota-derived imidazole propionate predicts cardiometabolic risk in patients with coronary artery disease. European Heart Journal, advance article, 2025. https://academic.oup.com/eurheartj/advance-article/doi/10.1093/eurheartj/ehaf661/8243926
3. Koh, A. et al. Microbially Produced Imidazole Propionate Impairs Insulin Signaling through mTORC1. Cell, 175(4):947–961, 2018. https://www.sciencedirect.com/science/article/pii/S0092867418313060
4. The gut metabolite imidazole propionate is a potential biomarker of and therapeutic target for atherosclerosis. Nature Reviews Cardiology, 2025. https://www.nature.com/articles/s41569-025-01200-8
5. Wang, A. et al. Histidine Intake, Human Gut Microbiome, Plasma Levels of Imidazole Propionate, and Coronary Heart Disease Risk in US Adults. Current Developments in Nutrition, 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC9194292/