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Enhörning S. et al. 2018

Water supplementation reduces copeptin and plasma glucose in adults with high copeptin: the H2O Metabolism pilot study

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Because elevated copeptin, a marker of vasopressin, is linked to low water intake and high diabetes risk, we tested the effect of water supplementation on copeptin and fasting glucose.

Design, Setting, and Participants


Addition of 1.5 L water daily on top of habitual fluid intake for 6 weeks.

Main outcome measure

Pre- and postintervention fasting plasma copeptin concentrations.


Reported mean water intake increased from 0.43 to 1.35 L · d−1 (P < 0.001), with no other observed changes in diet. Median (interquartile range) urine osmolality was reduced from 879 (705, 996) to 384 (319, 502) mOsm · kg−1 (P < 0.001); urine volume increased from 1.06 (0.90, 1.20) to 2.27 (1.52, 2.67) L · d−1 (P < 0.001); and baseline copeptin decreased from 12.9 (7.4, 21.9) pmol · L−1 to 7.8 (4.6;11.3) pmol · L−1 (P < 0.001). Water supplementation reduced fasting plasma glucose from a mean (SD) of 5.94 (0.44) to 5.74 (0.51) (P = 0.04). The water-associated reduction of both fasting copeptin and glucose concentration in plasma was most pronounced in participants in the top tertile of baseline copeptin.


Water supplementation in persons with habitually low water consumption and high copeptin levels is effective in lowering copeptin. It appears a safe and promising intervention with the potential of lowering fasting plasma glucose and thus reducing diabetes risk. Further investigations are warranted to support these findings.

A word from our expert: Dr Tiphaine Vanhaecke, Health and Hydration Scientist, Danone Research France

"This paper examines the effects of six weeks of increased water intake on copeptin and fasting plasma glucose. This is the first paper to show that increasing water intake is effective in reducing both plasma copeptin and fasting plasma glucose in healthy low-drinkers with high plasma copeptin."