Work

Optimizing blue poo: A validated, cost-effective method for measuring whole gut transit time

Year: 2025

Type: article

Abstract: Whole gut transit time (WGTT) provides essential insights into gastrointestinal health, but traditional measurement methods are often expensive or invasive. This study optimizes and validates the "blue dye method," an affordable and minimally invasive approach to WGTT measurement. Using "Hollinger Farbpulver Blau" (containing food colors E131 and E132), dye concentrations ranging from 30 mg to 241 mg were tested across four modes of delivery: capsule with liquid, gummy bear, muffin, and capsule with rice crackers and liquid. Each presented limitations: capsules taken with liquid led to inconsistent transit times, gummy bears caused staining, and muffins were perishable. Measured WGTTs varied between 18 and 29 hours depending on the mode of delivery and dye concentration. Optimal protocol was a capsule containing 60 mg of dye taken with two rice crackers and liquid, ensuring accurate detection without practical inconveniences. The standardized and optimized blue dye method provides valid WGTT measurements, making it well suited for large-scale population studies and clinical applications. Uses a simple blue dye as a marker for gut transit Tested several modes of delivery and concentrations to find the most practical option Established a standardized protocol for reliable and reproducible measurement Graphical abstract summarizing the optimized blue dye method developed in this study: It illustrates four modes of delivery tested for administering blue food dye: capsule with liquid, gummy bear, muffin, and capsule with rice crackers and liquid. Furthermore, it shows the four dye concentrations that were tested: 241 mg, 120 mg, 60 mg and 30 mg of colorant. The capsule ingested with liquid showed inconsistent transit times. The gummy bear was unpalatable and caused staining of fingers, teeth, and mouth, reducing user acceptability. The muffin functioned well but was perishable, limiting practicality. The optimal mode of delivery, a capsule ingested with rice crackers and liquid, achieved reliable and accurate measurements of whole gut transit time, without the disadvantages of other modes of delivery. The optimal concentration was 60 mg of colorant, as this represented the lowest dose at which blue stool was reliably observed. Created in BioRender. Schmandt, C. (2026) https://BioRender.com/jgou2z3

Source: MethodsX

DOI: 10.1016/j.mex.2025.103741

Authors: Cyra Schmandt, Julia Trunz, Claudio Perret, Anneke Hertig-Godeschalk, Zeno Stanga, Jivko Stoyanov