Abstract
Intestinal permeability is the passage of potentially harmful substances from the intestinal lumen into the internal environment of the body. The purpose of this study was to determine if resting hydration status influences intestinal permeability. It was hypothesized there would be a positive relationship between urine specific gravity and urine osmolality (i.e., measures of hydration status) and intestinal permeability. Twelve healthy, young adults (8 females and 4 males; mean age = 21 ± 1 years) participated in the study. Following an overnight fast, each subject provided a first morning urine sample then ingested a 150 mL solution containing 5 grams of lactulose (L) and 2 grams of mannitol (M). For the following 5 hours, all the urine was collected in a urine collection container. Samples of the urine were analyzed for urine specific gravity, urine osmolality, and L and M. The L and M concentrations were multiplied by the 5-hour urine volume to determine the urinary excretion of each probe, and the percent urinary excretion was determined by dividing the amount excreted by the dose ingested. Then, the L-to-M percent urinary excretion ratio was determined (L/M; an index of small intestinal permeability). There was a statistically significant (P < 0.05) correlation between L/M and urine specific gravity (R = 0.75) and urine osmolality (R = 0.664). L/M was significantly higher in individuals with a urine osmolality greater than 500 mOsm.kg-1 H2O (median = 0.063) compared to those below 500 mOsm.kg-1 H2O (median = 0.023). These results indicate resting hydration status may influence intestinal permeability in healthy, young adults.