Urolithins: a Comprehensive Update on their Metabolism, Bioactivity, and Associated Gut Microbiota.
Level 5 - mechanism / opinion, no new human data
Narrative review of preclinical literature and preliminary human studies
PubMed 35118817 · doi:10.1002/mnfr.202101019
What was done
This review synthesized literature from the preceding five years regarding urolithins—gut microbiota-derived metabolites of ellagitannins and ellagic acid found in foods like pomegranates, walnuts, and strawberries. It examined the chemical diversity of urolithins, their tissue and fluid distribution in humans, the microbial ecology defining specific metabotypes (UM-A, UM-B, UM-0), and the bioactivity and safety profile of urolithin A across preclinical models and initial human trials.
What was found
Thirteen urolithins and their conjugated derivatives (glucuronides, sulfates) have been detected across multiple human tissues and biofluids, including urine, blood, feces, breastmilk, prostate, colon, and breast tissue. The abstract reports no numerical effect sizes or quantitative outcome statistics.
Why it matters
It organizes the current understanding of how dietary polyphenols are converted into active metabolites and highlights gut microbiome-dependent metabotypes that may explain individual variations in health responses.
Limits
The paper is a non-systematic narrative review without standardized quality appraisal or quantitative synthesis. As noted in the abstract, many published in vitro studies used non-physiological concentrations or non-conjugated molecular forms, questioning reported mechanisms, and human intervention evidence remains in early stages.
Cited by
- supports Urolithin A is produced by gut bacteria from ellagitannins found in foods such as pomegranates.
- supports Urolithin A is a metabolite produced by the gut microbiome from ellagitannin polyphenols found in foods like pomegranates, raspberries, and walnuts.