A Novel Stable Isotope Approach for Determining the Impact of Thickening Agents on Water Absorption

Research on the bioavailability of water from thickened fluids has recently been published and it concluded that the addition of certain thickening agents (namely, modified maize starch, guar gum, and xanthan gum) does not significantly alter the absorption of water from the healthy, mature human gut. Using xanthan gum as an example, our “proof of concept” study describes a simple, accurate, and noninvasive alternative to the methodology used in that first study, and involves the measurement and comparison of the dilution space ratios of the isotopes ²H and ¹⁸O and subsequent calculation of total body water. Our method involves the ingestion of a thickening agent labeled with ²H 1 day after ingestion of ¹⁸O. Analyses are based on the isotopic enrichment of urine samples collected prior to the administration of each isotope, and daily urine samples collected for 15 days postdosing. We urge that further research is needed to evaluate the impact of various thickening agents on the bioavailability of water from the developing gut and in cases of gut pathology and recommend our methodology.