Rapid water transfer from extracellular to intracellular spaces following oral ingestion

Research on the effects of oral ingestion on extracellular and intracellular water balance is scarce. To measure the postprandial change in extracellular-intracellular water balance, 28 healthy adults (mean age 39 years, 20 women, 8 men) were recruited, and their extracellular-intracellular water distribution was measured at five time points: immediately before lunch (fasting), immediately after lunch (postprandial), and 30, 60, and 120 min after lunch using a BCM® body composition measuring device (Fresenius Medical Care, Germany). The results did not show significant changes in the total water volume, whereas the extracellular-intracellular distribution ratio decreased significantly from 0.7468 ± 0.0496 during fasting to 0.7376 ± 0.0473 during postprandial periods, which gradually increased over the next 120 min (0.7491 ± 0.0569). The estimated mean postprandial loss of extracellular fluid was 132 mL. Overall, oral ingestion promotes the transient transfer of body water from extracellular to intracellular spaces.