The Acute Effect of Water Intake on Glucose Regulation in Low Drinkers

Previous evidence suggests the hormone arginine vasopressin (AVP) may be a modifiable factor contributing to hyperglycemia. Significant differences in urine concentration and copeptin, a marker for AVP, have been observed between low and high water drinkers. Purpose: The purpose was to investigate the acute effect of adequate water intake on glucose regulation in low drinkers. Methods: 7 healthy (5 males, 2 female) low drinkers were recruited using a water frequency questionnaire (WFQ), spot and 24-h urine sample (age 43±6 y, BMI 30.9±3, WFQ volume 823±403 mL∙d-1, 24 h Uosm 961±105 mmol∙kg-1, copeptin 8.17±3.05 pmol∙L-1). During two experimental protocols, participants remained in the laboratory for 11 h and were provided either the Institute of Medicine’s (IOM) recommended amount of water excluding food (males: 3 L, females: 2 L) or an amount representing the bottom quartile of water consumption observed in the National Health and Nutrition Examination Survey (NHANES) (males: 0.5 L, females: 0.4 L). Food was provided to participants and standardized to body weight (100 kJ∙Kg-1) using a consistent ratio of macronutrients. Results: 11 h urine volume was significantly higher in the high water trial (P \u3c 0.001). 11 h UOsm was significantly higher in the low water trial (P \u3c 0.001). Plasma osmolality was acutely lower as a result of increased water intake (P = 0.007). Copeptin was suppressed as a result of high water intake (P = 0.019). Glucagon was similar between trials (P = 0.372), however, there was a main effect of water intake on cortisol (P = 0.009). No differences in plasma glucose were found due to water intake (P = 0.07). Conclusion: Acute increases in water intake do not reduce post-prandial plasma glucose responses in low drinkers, however, cortisol may be acutely reduced