Acute Increases in Water Consumption Supress Copeptin in Low Drinkers

Abstract Objectives To assess the acute effect of adequate water consumption on copeptin, a marker of arginine vasopressin, in low drinkers. Methods Six healthy (5 males, 1 female) low drinkers (age 43 ± 7 y, BMI 30.5 ± 3) were recruited based on self-reported daily water consumption ≤1.5 L·day−1 in males or 1.0 L·day−1 in females (854 ± 432 mL·d−1) and 24-h urine osmolality ≥800 mmol·kg−1 (968 ± 114 mmol·kg−1). Participants completed two counterbalanced crossover 11-h protocols. They were provided either the Institute of Medicine's recommended amount of water excluding food (males: 3 L, females: 2 L, HWI) or an amount representing the bottom quartile of water consumption observed in the National Health and Nutrition Examination Survey (males: 0.5 L, females: 0.4 L, LWI). Food was provided to participants and standardized to body weight (100 kJ·Kg−1) using a consistent ratio of macronutrients. Blood samples were collected at hours 700, 800, 900, 1200, 1300, 1400, 1600, 1700, and 1800. Results There was a significant main effect of water intake on plasma osmolality (F = 11.838, P = 0.018) with greater values in LWI at 1200 (HWI: 287 ± 3, LWI: 291 ± 3; P = 0.013), 1400 (HWI: 287 ± 4, LWI: 291 ± 5; P = 0.049), and 1700 (HWI: 287 ± 2, LWI: 292 ± 4; P = 0.004). There was also a significant main effect of water intake on copeptin (F = 9.848, P = 0.026) with higher values in LWI at 0800 (HWI: 6.1 ± 2.3, LWI: 8.7 ± 3.7; P = 0.016), 0900 (HWI: 5.3 ± 2.4, LWI: 9.2 ± 4.5; P = 0.013), 1200 (HWI: 4.2 ± 1.9, LWI: 7.8 ± 4.6; P = 0.021), 1400 (HWI: 4.3 ± 1.8, LWI: 8.3 ± 4.7; P = 0.033), 1600 (HWI: 4.7 ± 2.5, LWI: 7.6 ± 4.5; P = 0.049), and 1800 (HWI: 4.4 ± 2.5, LWI: 7.8 ± 5.2; P = 0.048). Water intake did not influence change in plasma volume (P = 0.214). Conclusions Copeptin was suppressed in response to acute increases in water consumption via suppression of plasma osmolality. Copeptin may serve as a sensitive marker for changes in total water intake. Funding Sources This study was supported by Arizona State University College of Health Solutions.