A common vitamin could influence bathroom frequency

The study was carried out by an international research team led by Mauro D'Amato, Professor of Medical Genetics at LUM University and Ikerbasque Research Professor at CIC bioGUNE, member of BRTA. The researchers used a large-scale genetic strategy to look for common DNA differences linked to how often people have bowel movements, referred to in the study as stool frequency. To do this, they analyzed genetic data and health questionnaires from 268,606 individuals of European and East Asian ancestry. Advanced computational methods helped identify which genes and biological processes were most strongly connected to gut movement.

Known Gut Pathways Confirm the Findings

The analysis uncovered 21 regions of the human genome that influence bowel movement frequency, including 10 regions that had not been identified before. Many of the genetic signals pointed to biological systems already known to regulate gut motion, offering reassurance that the results fit with established biology. These included bile-acid regulation (bile acids help digest fats and also act as signaling molecules in the gut) and nerve signaling involved in intestinal muscle contractions (including acetylcholine-related signaling, which helps nerves communicate with muscle). Together, these findings reinforce existing knowledge about how the gut functions.

Vitamin B1 Stands Out as a Surprise Signal

The most notable discovery emerged when researchers focused on two high-priority genes connected to vitamin B1 biology. These genes, SLC35F3 and XPR1, play a role in how thiamine is transported and activated in the body. To see whether this genetic signal was reflected in everyday life, the team analyzed dietary data from the UK Biobank. Among 98,449 participants, higher intake of dietary thiamine was linked to more frequent bowel movements.

This relationship was not uniform across all individuals. The effect of thiamine intake on bowel movement frequency depended on genetic variation in the SLC35F3 and XPR1 genes (analysed together as a combined genetic score). These results suggest that inherited differences in how the body handles thiamine may shape how vitamin B1 intake influences bowel habits in the general population.

Links to IBS and Future Research

Dr. Cristian Diaz-Muñoz, the study's first author, said "We used genetics to build a roadmap of biological pathways that set the gut's pace. What stood out was how strongly the data pointed to vitamin B1 metabolism, alongside established mechanisms like bile acids and nerve signaling."

The findings also suggest a meaningful biological connection between bowel movement frequency and IBS, a condition that affects millions of people worldwide. "Gut motility problems sit at the heart of IBS, constipation and other common gut-motility disorders" says Prof Mauro D'Amato, "but the underlying biology is very hard to pin down. These genetic results highlight specific pathways, especially vitamin B1, as testable leads for the next stage of research, including lab experiments and carefully designed clinical studies."

The study was led by Mauro D'Amato's Gastrointestinal Genetics Research Group and involved investigators from CIC bioGUNE in Spain, LUM University, Institute for Genetics and Biomedical Research - CNR, CEINGE and University of Naples Federico II in Italy, University of Groningen in The Netherlands, University of Oxford in UK, Concordia University and Ontario Institute for Cancer Research in Canada, and Monash University in Australia. The research was supported by grants from MCIU/AEI/10.13039/501100011033 and ERDF/EU (PID2023-148957OB-I00); PRIN2022/NextGenerationEU (2022PMZKEC; CUP E53D23004910008 and CUP B53D23008300006); ERC Starting Grant (101075624); PNRR/NextGenerationEU (PE00000015/Age-it); NWO-VICI (VI.C.232.074); NWO Gravitation ExposomeNL (024.004.017); EU Horizon DarkMatter program (101136582).