Water has been described as the most essential nutrient neglected, underappreciated, and under researched. Hydration—defined as the body’s real-time water status—plays a fundamental role in maintaining short-term physical performance, cognitive function, and overall physiological safety. Its relevance becomes even more pronounced during intense physical activity, exposure to hot or humid environments, or situations where access to clean drinking water is restricted. Adequate hydration supports thermoregulation, cardiovascular stability, and metabolic efficiency, making it an essential factor for preventing heat-related illnesses, fatigue, and performance decline.
Hydration Dynamics and Metabolic Health
Multiple associations have been reported between fluid intake and metabolic health outcomes, including chronic kidney disease (CKD), recurrence of kidney stones, and some metabolic markers of hyperglycemia. It is difficult to measure the levels of vasopressin, the primary hormone responsible for regulating water reabsorption in the kidney, under normal circumstances, as its concentration in the blood is quite low.
Water's importance for the prevention of nutrition-related noncommunicable diseases has received more attention recently because of the shift toward consumption of large proportions of fluids as caloric beverages. It is well-known that the hyperglycemia characteristic of diabetes presents unique challenges to body water balance. Elevated blood glucose exerts osmotic pressure which elicits an internal shift in body water from the intracellular to the extracellular space, preserving blood osmolality and volume at the cost of cellular dehydration
Optimizing Water Intake for Better Metabolic Outcomes
- Linking low water intake, low urine output, or high Arginine Vasopressin (AVP) to various health outcomes or risk factors suggest that maintaining the hydration state in the face of habitual low intake has a cost. The entire process of hydration (from what goes in, to what comes out, to what happens internally to maintain body water homeostasis) may be more important than the hydration state when considering implications for kidney or cardiometabolic health.
- Higher water intake has consistently been associated with lower blood glucose levels and risk of diabetes in men, but not in women.
- AVP (and copeptin) also tends to be higher in men than in women.
- Individuals with low fluid intake have higher AVP and copeptin concentrations as compared to those who consume more fluids despite similar plasma osmolality.
Way to support long-term metabolic wellbeing
In order to ensure optimal hydration, it is proposed that
- Optimal total water intake should approach 2.5 to 3.5 L day to allow for the daily excretion of 1.5 to 2 L of dilute (< 500 mOsm kg−1) urine. Simple urinary markers of hydration such as urine color or void frequency may be used to monitor and adjust intake.
- Regardless of sex, individuals with higher circulating AVP and other signs of insufficient hydration appear to be the best candidates for a water intervention to lower AVP and metabolic risk.
- Improving hydration by increasing water intake may provide a simple and inexpensive intervention to help prevent the development of metabolic dysfunction.
- Maintain regular meal timings to support circadian rhythm and metabolic balance.
- Manage stress proactively through mindfulness, breathwork, or recovery routines to reduce cortisol-driven metabolic disruption.
