Gut-vascular axis
You want this balanced, not maximized. Gut bacteria ferment what reaches them into compounds that enter the bloodstream; some relax vessels, some do the opposite. The reason this pathway exists is a finding that explains something the rest of the map cannot. In one double-blind crossover, eight of fourteen participants responded to a polyphenol with a real ambulatory pressure drop — and the responders were distinguishable from the non-responders by their baseline stool: higher phenylpropionic and phenyllactic acids, and a higher abundance of Fusicatenibacter bacteria. That is the clearest account of non-response anywhere in this evidence base. Some people cannot metabolize the active compound into the form that works. It is also why “it did nothing for me” and “it worked” can both be true reports of the same substance.
In depth
Gut microbial metabolites — short-chain fatty acids, tmao and community composition.
What drives it
Gut barrier increases it.
Short-chain fatty acids and related metabolites are produced in situ by resident colonic microbiota from host-delivered dietary substrate. doi 10.2147/JIR.S292544
What it drives
It reduces Blood pressure.
Gut-microbiota modulation lowers blood pressure, but modestly. Dong JY, Szeto IMY, Makinen K, et al., “Effect of probiotic fermented milk on blood pressure: a meta-analysis of randomised controlled trials”, Br J Nutr 2013;110(7):1188-94 (doi 10.1017/S0007114513001712): 14 randomized placebo-controlled trials, 702 hypertensive patients — mean decrease of 3.10 mmHg systolic and 1.09 mmHg diastolic. Corroborated by a larger recent synthesis, “Modulating Gut Microbiota To Control Hypertension: A Systematic Review and Meta-Analysis of Probiotics, Postbiotics, Prebiotics and Synbiotics” (doi 10.1007/s12602-026-10944-9), which searched PubMed, Scopus, Cochrane Library, ProQuest and ScienceDirect from inception to 30 July 2025 and pooled 33 RCTs in hypertensive and pre-hypertensive individuals. the effect size is small (~3 mmHg systolic) and is measured in hypertensive / pre-hypertensive people — not a demonstrated effect in normotensives. The 2013 meta rests on fermented milk specifically, so strain, dose and matrix are not interchangeable across products. doi 10.1017/S0007114513001712
It increases Gut barrier.
Verbatim: 'One of the prominent features in clinically silent phase before the onset of t1d is the presence of a microbiota characterized by low numbers of commensals butyrate producers, thus negatively influencing the gut permeability' (pmc9737253). Sign act: microbial metabolites up means barrier integrity up. The probiotic intervention study was null - 'Probiotic intervention in infancy is not associated with development of beta cell autoimmunity and type 1 diabetes' (doi 10.1007/s00125-018-4738-4). This edge describes a mechanism that a supplementation trial has already failed to exploit, and that failure is recorded here beside it. doi 10.1007/s00125-018-4738-4
Blends that modulate it
Each blend page names this pathway and carries the study behind its claim.
See it on the map
Open the causal map to follow this pathway upstream and downstream, arrow by arrow, each with its study.