Does the appearance of the Magenstrasse depend on the amount of water consumed?

The Magenstrasse (stomach road) is a phenomenon describing the rapid evacuation of water drunken after a solid meal from the stomach. So far, its existence has been demonstrated for water volumes of 150 mL or more. The aim of this three-arm, randomised, cross-over, 12-subject study was to investigate whether the Magenstrasse is also present for smaller water volumes. For this purpose, gastric emptying of 50, 100 or 150 mL of water that was administered after a light meal was determined using MR imaging. With each dose of water, a fast-dissolving compression coated tablet containing caffeine and iron oxide as well as a hard capsule containing stable isotope labelled caffeine and medium-chain triglycerides were administered. This made it possible to determine the initial localization of the respective forms in the stomach on MR images as a function of the amount of water drunk, and also to determine the emptying rates of the two caffeine variants using saliva samples that were obtained in the study and quantified using LC-MS/MS. Gastric emptying of the ingested water was rapid and usually completed after approximately 20 min, regardless of the applied volume. In contrast to the consumed water, gastric emptying of natural caffeine and stable isotope labelled caffeine was delayed. The capsule usually floated on liquid and chyme, whereas the compression coated tablet was often embedded in chyme.