Researchers at Sheba Medical Center and Tel Aviv University have validated a Microbial Health Index (MHI) as a composite biomarker for overall physical and mental well-being in a cohort of 893 adults who underwent routine executive medical checkups. The index is calculated as the log ratio of 97 health-associated bacterial amplicon sequence variants to 31 disease-associated variants, yielding a single per-person score from 16S ribosomal RNA sequencing of fecal samples.
Participants provided detailed lifestyle and food-frequency questionnaires, electronic medical records, laboratory results, ICD-10 diagnoses, medication classes, and Bruce-protocol cardiac stress-test data. Higher MHI scores correlated with greater fiber intake, adherence to a Mediterranean diet, and higher metabolic equivalents (METs) on the stress test, while ultra-processed food consumption and subclinical inflammation markers correlated with lower scores.
The study found that the MHI reflects modifiable factors even among individuals with existing conditions such as hypertension or metabolic syndrome. Regression models adjusting for age, sex, lifestyle, and background medical conditions estimated that specific dietary and exercise changes could shift an individual's MHI by 0.5 points, a magnitude previously linked to multiple disease outcomes.
Drawing on published intervention studies, the authors report that the MHI responds rapidly to dietary modification and moves within the predicted range, suggesting it functions as a sensitive, dynamic reporter of health status comparable to blood pressure or lipid panels.
The index condenses complex microbial ecology into an actionable metric, addressing a longstanding barrier to clinical use of microbiome data. The authors note that the same bacterial variants appear linked to both disease and lifestyle effects, implying these microbes respond to host exposures rather than directly causing health outcomes.
The findings were published in Gut Microbes (2026) by Tzipi Braun, Yael Haberman, and colleagues (DOI: 10.1080/19490976.2026.2719055).
A gut microbial health index as a composite biomarker for evaluating overall health
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