Dietary fiber supplement shows promise for fatty liver, with effects linked to gut microbiota

by University of Eastern Finland

edited by Lisa Lock, reviewed by Robert Egan

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A new study is the first to investigate the effects of prebiotic xylo-oligosaccharides (XOS) on fatty liver in humans. The findings suggest the fiber supplement may reduce harmful metabolic byproducts in the gut and thereby improve liver health. Importantly, the composition of the gut microbiota before supplementation influences the benefits observed. The study was conducted by researchers from the University of Jyväskylä and the University of Eastern Finland and is published in npj Gut and Liver.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a common comorbidity of overweight and obesity, affecting about 75% of individuals with excess weight. If left untreated, the condition may progress to liver cirrhosis or even liver cancer. Lifestyle changes remain the primary treatment approach, but adherence is often challenging, highlighting the need for complementary therapies.

Fiber supplement reduces harmful gut metabolites

For the study, 42 overweight adults consumed 2.8 grams of XOS prebiotic daily for four months. Prebiotics are dietary fibers that are not digested by human enzymes but instead reach the colon, where they support the balance of the gut microbiota. Liver fat content was assessed using magnetic resonance imaging before and after the intervention.

The results showed XOS reduced levels of certain harmful amino acid-derived metabolites in the gut, which have previously been linked to liver fat accumulation.

"Our findings suggest that, when applied to the right target group, XOS can restore gut fermentation balance, reduce the production of harmful metabolites and thereby benefit liver health," says the first author of the study, Jukka Hintikka, a postdoctoral researcher at the University of Eastern Finland.

Baseline gut microbiota influenced response to intervention

The prebiotic appeared to be most effective in individuals with an initially imbalanced gut microbiota. These individuals showed signs of increased protein fermentation relative to carbohydrate fermentation in the gut. XOS supplementation helped rebalance microbial composition. In this subgroup, a reduction in visceral fat was also observed.

In contrast, the effect of the prebiotic was weaker, or not observed at all, in participants whose blood markers suggested more advanced stages of fatty liver disease.

This study is the first clinical trial in humans to examine the effects of XOS prebiotics on liver fat. The findings are consistent with earlier animal studies, in which XOS reduced fatty liver in rats.

"In the future, our findings may contribute to the development of personalized treatments for fatty liver disease," says Hintikka. "However, larger and more targeted studies are still needed to confirm these results."

More information

Jukka E. Hintikka et al, Prebiotic xylo-oligosaccharides for alleviation of hepatic steatosis: results from a four-month dietary intervention and determinants of response, npj Gut and Liver (2026). DOI: 10.1038/s44355-026-00066-y

Key medical concepts

Flora, IntestinalAbdominal Visceral Fats

Clinical categories

GastroenterologyDigestive health Provided by University of Eastern Finland Who's behind this story?

Lisa Lock

BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021. Full profile →

Robert Egan

Bachelor's in mathematical biology, Master's in creative writing. Well-traveled with unique perspectives on science and language. Full profile →

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