Do ACE Inhibitors and ARBs Change Your Gut Microbiome?

ACE inhibitors and angiotensin receptor blockers (ARBs) lower blood pressure by acting on the renin-angiotensin system. In rodents, they may also alter the gut microbiome. That idea is biologically plausible, but it has not survived a meaningful human test. The best current reading is cautious: these drugs may change gut ecology in specific animal models, often at high exposures, yet no credible evidence shows that standard clinical use reliably reshapes the human microbiome for better or worse.

A 2025 systematic review by Wang et al. found eight rodent studies and just one human study of ACE inhibitors or ARBs and the gut microbiome. The imbalance is the story. Animal results can generate a useful hypothesis; they cannot establish what happens in people taking a prescribed dose of losartan, irbesartan, or captopril.

Why the hypothesis makes biological sense

The intestine has its own local renin-angiotensin system. Angiotensin II may promote intestinal inflammation and permeability and may make the gut less friendly to obligate anaerobic bacteria by constricting mesenteric blood vessels and increasing intestinal oxygen tension. In that model, blocking the system could improve barrier function and favor short-chain-fatty-acid-producing microbes.

The proposed pathway has another direction, though. Some gut organisms, including Bifidobacterium bifidum, have direct ACE-inhibitory activity. Microbes could therefore affect response to blood-pressure drugs rather than simply respond to them. Wang et al. identify this two-way relationship as unresolved. A microbiome shift after treatment would not, by itself, prove that the drug caused it through intestinal RAS signaling.

Human hypertension does have a reproducible microbiome context. A 2025 systematic review and meta-analysis of prebiotic trials reported that people with hypertension tend to have lower abundances of several short-chain-fatty-acid-associated genera, including Roseburia, Faecalibacterium, Bifidobacterium, Coprococcus, and Akkermansia. Prebiotic interventions partly restored these taxa in human randomized trials, with associated blood-pressure reductions. That supports plausibility. It does not show that ACE inhibitors or ARBs reproduce those effects.

What the rodent studies found

Across the eight animal studies in the Wang review, the most repeated taxonomic signal was higher Lactobacillus abundance: three studies reported it, all with ARBs—candesartan, valsartan, and irbesartan. Four ARB studies reported a lower Bacteroidetes-to-Firmicutes ratio, while none of the three captopril studies did. Two studies reported higher Bifidobacterium, and two captopril studies reported higher Parabacteroides. Other reported taxa appeared in only one study each.

The diversity results suggest a possible drug-class difference, but they do not settle one. All four studies that reported increased alpha and beta diversity used ARBs; all three captopril studies found no diversity change. Captopril still improved some intestinal measures, including tight-junction proteins and inflammation markers, in the reviewed studies. Diversity is a descriptive microbiome metric, not a clinical endpoint, and these results do not establish that more diversity caused a health benefit.

Short-chain fatty acids add another layer of uncertainty. Three of four rodent studies that measured them reported increases in butyrate, propionate, acetate, or some combination; one captopril result was not statistically significant. The valsartan study by Qi et al. moved in the other direction, reporting lower isobutyrate and isovalerate. The review provides directional changes but no pre/post concentrations, effect sizes, or p-values for these outcomes. Without magnitude or precision, no one can tell whether the differences were biologically meaningful.

The human evidence does not match the animal story

The sole human study summarized in the review examined losartan users and found no significant change in alpha or beta diversity. Its reported taxa changes—higher Odoribacter and Clostridium, lower Staphylococcus, Enterobacter, and Klebsiella—did not overlap with the rodent predictions. The study did not report dose or treatment duration and appears to have pooled ACE-inhibitor and ARB users without stratification. Those gaps prevent a clean class-specific conclusion, but the result certainly does not validate the rodent pattern.

The animal literature has its own internal contradiction. In the Qi et al. valsartan experiment, rodents had decreased microbial diversity, lower isobutyrate and isovalerate, and no improvement in gut permeability. That differs from the broader claim that ARBs consistently increase diversity and support short-chain-fatty-acid production. Dose, timing, delivery method, and animal model could explain the disagreement, but the studies do not provide a consistent pharmacological signature.

Rodent dose and model choices limit translation

Most of the animal work used spontaneously hypertensive rats, an inbred model of severe, early-onset genetic hypertension. Seven of eight studies used that model; one used a DOCA-salt model. Neither captures the usual mix of genetics, diet, body weight, aging, and metabolic disease behind human hypertension.

The doses also matter. Using FDA Km-based allometric conversion, a 50 mg/kg/day captopril dose in rats converts to about 590 mg/day for a 70-kg person, about 1.3 times the 450 mg/day maximum clinical dose. A 250 mg/kg/day captopril dose converts to roughly 2,930 mg/day, about 6.5 times that maximum. Losartan at 20 mg/kg/day converts to about 226 mg/day, about 2.3 times its 100 mg/day maximum. Irbesartan at 27 mg/kg/day converts to about 316 mg/day, close to its 300 mg/day clinical ceiling. These are not all cartoonishly distant from clinical practice, but several exceed it, and none of the studies establishes a dose-response relationship.

Does more butyrate lower blood pressure?

That assumed final step also lacks human support. In a 2024 randomized, placebo-controlled trial of oral butyrate in people with hypertension, Verhaar et al. found no significant blood-pressure reduction. The trial does not prove that microbial short-chain fatty acids never affect cardiovascular biology. It does show that oral butyrate, at the tested achievable intervention, did not deliver the clinical result that the mechanism predicts.

For perspective, several lifestyle interventions have direct human blood-pressure evidence without requiring a speculative drug-microbiome chain. A 2024 umbrella review of dietary evidence found support across many meta-analyses for dietary approaches to blood-pressure management. A 2025 dose-response meta-analysis of 75 nitrate RCTs involving 1,823 participants also reported lower systolic blood pressure per additional millimole of dietary nitrate. Those findings do not replace prescribed treatment; they show what human intervention evidence looks like when the endpoint is blood pressure rather than a microbial surrogate.

What to do with this information

Do not choose, stop, or switch an ACE inhibitor or ARB because of a hoped-for microbiome effect. These medications have established indications and risks that require a clinician's guidance. The gut hypothesis remains preclinical: Wang et al. found no registered prospective human trials that treated the microbiome as a primary or secondary endpoint of ACE-inhibitor or ARB therapy.

A fiber-rich, prebiotic-containing dietary pattern is a more evidence-based way to support short-chain-fatty-acid-producing microbes than assuming a blood-pressure pill will do it. Even there, avoid turning a plausible microbiome change into a promise of cardiovascular benefit. The next useful study would randomize people to a defined ACE inhibitor or ARB dose, measure microbiome and metabolite changes over time, and test whether any shift tracks with clinically meaningful outcomes. Until then, ACE-inhibitor and ARB pharmacomicrobiomics is an interesting rodent finding in search of human confirmation.