June 19, 2025, 9:02 am | Read time: 5 minutes
A new study shows that certain metabolic products in stool can help better predict the mortality of critically ill intensive care patients. This could be another step toward personalized medicine–with concrete opportunities for prevention and therapy.
Daily bowel movements are a natural process of our metabolism, where substances not utilized by digestion are excreted. According to a previous study from 2024, two to three bowel movements per day are particularly healthy (FITBOOK reported). However, the content of the excreted substances also provides information about our health. Researchers have now found that the bacteria in stool can be used to estimate the life expectancy of patients in intensive care.
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Overview
Potential Biomarker for Identifying Patients with Increased Mortality Risk
Critically ill patients in intensive care often develop dangerous syndromes like sepsis or acute respiratory distress. The causes are highly individual, varying from patient to patient, complicating treatment. Additionally, patients respond differently to the same treatment.
Researchers are therefore trying to identify specific characteristics, known as biomarkers, to help treat certain symptoms more effectively. It is already known that critically ill individuals often have a lower bacterial diversity in their gut microbiome. Moreover, the composition of the metabolic products produced by their microbiome differs from that of healthy individuals.
A research team from the University of Chicago and the University of Amsterdam has now created an index of biomarkers in the stool of patients to estimate the risk of death within the next 30 days.1
How the Study Was Conducted
The international group of scientists focused on dysbiosis, also known as dysbacteriosis, an imbalance of microorganisms in the gut favoring harmful bacteria. This can also be caused by a poor diet high in sugar and refined flour products.2 Diseases and medications can also damage the gut flora and trigger dysbiosis.
To determine the role of bacterial imbalance in the gut flora of critically ill patients, stool samples from 196 critically ill patients were examined. The participants were at least 18 years old and had previously suffered respiratory arrest or shock. Pregnant individuals and patients with prior cardiac arrest upon admission were excluded.
For model validation (i.e., verifying the research method), 147 patients were assigned as a training cohort and 49 as a validation cohort to ensure accurate data. The analyzed data came from the training cohort. The researchers developed a metabolic dysbiosis score (MDS) that uses the concentrations of 13 metabolites (breakdown products) from the gut flora to predict 30-day mortality independently of other confounding factors.
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What Stool Reveals About the Life Expectancy of the Critically Ill
According to the study’s evaluation, the metabolic dysbiosis score (MDS) predicted mortality in the training cohort of intensive care patients with 84 percent accuracy. The sensitivity, or how well the MDS recognized mortality, was also high at 89 percent. The validation cohort showed similar values but lacked statistical significance due to the small sample size.
The results suggest that the MDS could serve as a biomarker in the future to predict the 30-day life expectancy of intensive care patients. The strong link between dysbiosis and increased mortality risk indicates that an imbalance in the microbiome plays a crucial role in health. However, further research is needed to validate these findings, the researchers emphasize.
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The MDS Could Help in Prevention and Risk Reduction
However, the study showed that stool not only indicates the life expectancy of critically ill patients. The data analysis also revealed that stool metabolites can determine which liver transplant patients have a higher risk of postoperative infections. This could serve as a preventive measure in the future to avoid early infection risks.
The metabolic breakdown products that make up the MDS include short-chain fatty acids, bile acids, and tryptophan metabolites. According to the researchers, they point to biological pathways that could be therapeutically targeted. This could be achieved through a targeted diet, the administration of probiotics, or the direct administration of specific metabolites.
As FITBOOK learned from Alexander de Porto, the study’s lead author, the identified state of metabolic dysbiosis points to biological processes that could be specifically influenced–for example, through dietary measures or the targeted administration of microorganisms that produce the protective metabolites lacking in at-risk patients. At the same time, the study still has limitations: The data collected so far comes from a single center. Whether the results can be applied to other patient groups must be clarified through further research. It is also unclear whether the observed correlations are causal effects–future intervention studies should address this.