Marker Guide

IPA producing microbes

What this marker measures

The microbial community's capacity to produce 3-indolepropionic acid (IPA), a tryptophan-derived metabolite. IPA may support intestinal barrier integrity, immune regulation, and control of intestinal inflammation¹⁻⁴, and has been associated with lower systemic inflammatory markers⁵⁻⁸.

Clinical associations

Consider this marker when your patient presents with:

Gut barrier concerns

Suspected increased intestinal permeability or gut barrier dysfunction

Intestinal or systemic inflammation

Chronic intestinal inflammation, IBD-type presentations, or low-grade systemic inflammation where tryptophan metabolites may contribute

Metabolic presentations

Type 2 diabetes, metabolic syndrome, insulin resistance

GI functional presentations

IBS-type symptoms where altered barrier or immune signalling may be relevant

Interpreting the result

All results are compared to Microba's healthy cohort to determine whether they fall within or outside the expected range.

LOW

IPA-producing potential is lower that expected

May indicate reduced capacity to support gut barrier integrity, immune regulation, and anti-inflammatory signalling.Action: see patient management insights below

Within Range

IPA-producing potential is within expected parameters

This suggests microbial capacity to support gut barrier and immune-regulatory pathways.

HIGH

IPA-producing potential is higher than expected

Usually favourable in isolation and may reflect stronger capacity to support gut barrier integrity and immune regulation. Interpret alongside symptoms, diet, and broader microbiome context

Patient management insights

Increase IPA production through dietary and probiotic support.

Dietary strategies

Inclusion of 3 serves per day of polyphenol-rich foods may increase fasting serum IPA in older adults⁵.
GRADE C

A Mediterranean diet may increase plasma IPA9,10. Foods rich in ellagic acid (e.g. pomegranate juice, chestnuts) may maintain plasma IPA levels¹¹.
GRADE D

Observational studies show an association between intake of wholegrain wheat and rye and higher plasma IPA⁸. (Observational data only)
GRADE PP H

Tips for patients discussion

Your report suggests a reduced capacity to produce IPA, a beneficial compound that helps support the gut lining and regulate inflammation. Eating more polyphenol- and fibre-rich foods such as berries, pomegranate, legumes, and wholegrains — may help support these microbes.

The community

IPA is not produced by a single species, it’s a community-level function. Here are some of the most commonly-detected species, however this list is not exhaustive.

Acidaminococcus fermentans
CAG-83 MIC6888
CAG-83 MIC7172
CAG-83 MIC7830
CAG-83 MIC8701
CAG-83 MIC8848
CAG-83 MIC9166
CAG-83 MIC9279
CAG-83 sp000435555
CAG-83 sp003487665
Clostridium_M MIC7663
Fusobacterium animalis
Fusobacterium_C gonidiaformans
Mogibacterium diversum
Mogibacterium sp002299625
Mogibacterium sp900315625
Peptostreptococcus anaerobius
Peptostreptococcus sp000758885
UBA5446 MIC8728
UBA9502 MIC6887
UBA9502 MIC7149
UBA9502 MIC9805
UBA9502 MIC9781

How results are calculated

All microbiome marker results are compared against the Microba Healthy Cohort — a purpose-built reference group of more than 450 healthy individuals, collected and analysed using the same workflow as patient samples.

Each marker is scored by comparing the patient's relative abundance against the cohort average. The distance from this average is expressed as standard deviations, and determines whether a result is classified as Low, Borderline, or High.

How the result scale works

▲ AVG (Healthy Cohort average)

The patient's relative abundance is compared to the Healthy Cohort average. A negative distance from average means the microbial group is less abundant than the Healthy Cohort. A positive distance means it is more abundant. Results falling outside the expected range are classified as borderline or high/low (borderline high/low:+/-0.68,andhigh/low:+/-1.28).

Evidence grading for patient management insights

The letter grades shown next to each patient management insight show the quality of the research behind it. Every insight provided has been through a rigorous review of the scientific literature and graded using the NHMRC Levels of Evidence, so you can see exactly how strong the evidence is before applying it in practice.

Source references for all clinical associations, interpretation definitions, and patient management insights on this card.

1. Gao, H. et al. Microbiota-derived IPA alleviates intestinal mucosal inflammation through upregulating Th1/Th17 cell apoptosis in inflammatory bowel disease. Gut Microbes 17, 2467235 (2025).
2. Chen, Y. et al. Indole‑3‑propionic acid alleviates intestinal epithelial cell injury via regulation of the TLR4/NF‑κB pathway to improve intestinal barrier function. Molecular Medicine Reports 30, 1–10 (2024).
3. Li, J. et al. Indole-3-propionic Acid Improved the Intestinal Barrier by Enhancing Epithelial Barrier and Mucus Barrier. J. Agric. Food Chem. 69, 1487–1495 (2021).
4. Venkatesh, M. et al. Symbiotic Bacterial Metabolites Regulate Gastrointestinal Barrier Function via the Xenobiotic Sensor PXR and Toll-like Receptor 4. Immunity 41, 296–310 (2014).
5. Peron, G. et al. A Polyphenol-Rich Diet Increases the Gut Microbiota Metabolite Indole 3-Propionic Acid in Older Adults with Preserved Kidney Function. Molecular Nutrition & Food Research 66, 2100349 (2022).
6. Cussotto, S. et al. Tryptophan Metabolic Pathways Are Altered in Obesity and Are Associated With Systemic Inflammation. Front. Immunol. 11, (2020).
7. Tuomainen, M. et al. Associations of serum indolepropionic acid, a gut microbiota metabolite, with type 2 diabetes and low-grade inflammation in high-risk individuals. Nutr & Diabetes 8, 35 (2018).
8. de Mello, V. D. et al. Indolepropionic acid and novel lipid metabolites are associated with a lower risk of type 2 diabetes in the Finnish Diabetes Prevention Study. Sci Rep 7, 46337 (2017).
9. Zhu, C. et al. Human gut microbiome composition and tryptophan metabolites were changed differently by fast food and Mediterranean diet in 4 days: a pilot study. Nutrition Research 77, 62–72 (2020).
10. Lécuyer, L. et al. Untargeted plasma metabolomic profiles associated with overall diet in women from the SU.VI.MAX cohort. Eur J Nutr 59, 3425–3439 (2020).
11. Yang, J. et al. Pomegranate Metabolites Impact Tryptophan Metabolism in Humans and Mice. Curr Dev Nutr 4, nzaa165 (2020).