The price of not drinking water
Chronic dehydration, inflammation, disease. In that order.
Water is at the forefront of nearly every health recommendation and is no longer an afterthought, as it was in prior decades. What is often missing, though, is the reason why water matters so deeply beyond its role in general hydration. Its role as a transport medium is foundational to human physiology, supporting everything from nutrient absorption and circulation to cellular metabolism and cognitive function. The entire delivery system slows down, compromising energy production, tissue repair, and overall metabolic efficiency.
Without sufficient water, essential nutrients cannot reach the areas where they are needed.
Water comprises approximately 60% of the adult human body, serving as the solvent for plasma, lymph, and interstitial fluids (Welsh & Prentice, 2023). These fluid compartments act as highways for the delivery of nutrients and substrates, utilizing water's polarity and fluid dynamics to dissolve, mobilize, and distribute molecules to target tissues. These include essentials like:
Glucose
Amino acids
Electrolytes
Hormones
Action prompt: Before thinking about what supplements to add or which foods to optimize, ask: Am I drinking enough water to deliver the nutrients I’m already consuming?
Transport begins at the cellular level, where water facilitates the diffusion and active transport across cellular membranes. As blood circulates, it delivers oxygen and nutrients to tissues and removes waste products, such as urea and carbon dioxide. This fluid flow depends on water’s contribution to blood volume and viscosity (Welsh & Prentice, 2023). Even mild dehydration (body water loss of just 1 to 2%) can reduce plasma volume, leading to decreased perfusion and impaired nutrient delivery (Robayo et al., 2024).
The consequences ripple out from there. Reduced fluid volume compromises cardiovascular efficiency, particularly during exertion. The brain, with its high metabolic demand and tightly regulated environment, is especially vulnerable. The cognitive effects of underhydration include:
Slowed reaction times
Impaired memory
Diminished executive function
These symptoms can likely be tied to decreased cerebral blood flow and altered neurotransmitter dynamics (Armstrong & Johnson, 2018; Robayo et al., 2024). In a chronically dehydrated state, these effects may be more than functional; they can also be structural, contributing over time to systemic low-grade inflammation and metabolic dysregulation.
Emerging evidence supports this concern. Armstrong and Johnson (2018) propose a model in which the brain acts as a homeostatic gatekeeper, modulating fluid intake through neuroendocrine signaling long before overt dehydration symptoms appear.
When total water intake drops below ~60 ounces per day, plasma levels of arginine vasopressin (AVP) rise. This is a sign the brain has shifted into conservation mode.
The compensatory response triggers renal water reabsorption, a process by which the kidneys reclaim water from the fluid that passes through them, thereby attempting to prevent dehydration and maintain a stable water balance. Urination is suppressed, and over time, these shifts can impair glucose regulation, increase oxidative stress, and disrupt nutrient transport efficiency (Armstrong & Johnson, 2018).
Consider tracking your baseline water intake for two or three days, especially on days when your brain is working hard or you’re physically active. Are you hitting 60+ ounces as a minimum, or are you operating below threshold without realizing it?
In this way, chronic underhydration becomes a silent disruptor. An individual may appear clinically stable, yet essential nutrients may not be reaching their intended destinations efficiently. The result is fatigue, inflammation, and metabolic inflexibility, and, in high-performing populations such as athletes or executives, a noticeable decline in output without a precise diagnosis.
More isn’t better
While underhydration is a common concern, overhydration—particularly when fluid intake far exceeds electrolyte replacement—can be equally problematic. Drinking excessive amounts of water without adequate sodium intake can dilute blood sodium levels, leading to hyponatremia, a condition marked by fatigue, confusion, nausea, and in severe cases, neurological impairment.
This is especially relevant for endurance athletes or individuals who consume large volumes of water rapidly. When plasma sodium levels drop too low, cells (including those in the brain) begin to swell, disrupting cellular function and potentially leading to severe consequences. Like all systems in the body, hydration requires balance, and more is not always better. Monitoring thirst, urine concentration, and electrolyte intake can help ensure that fluid intake supports homeostasis.
Ultimately, water is the current that carries the body’s biochemistry. Without it, even the most optimized diets or supplement regimens cannot deliver their full benefits. Supporting hydration is more than meeting arbitrary intake targets, because without enough of it, our body cannot protect the integrity of its transport system. This is especially true as we age, sweat more, or demand more from our brains and bodies.
Is your hydration strategy also supporting your electrolyte balance, or are you unintentionally diluting your system? Especially after sweating or engaging in intense activity, consider pairing water with foods or drinks rich in sodium and potassium.
References
Armstrong, L. E., & Johnson, E. C. (2018). Water Intake, Water Balance, and the Elusive Daily Water Requirement. Nutrients, 10(12), 1928. https://doi.org/10.3390/nu10121928
Robayo-Amortegui, H., Quintero-Altare, A., Florez-Navas, C., Serna-Palacios, I., Súarez-Saavedra, A., Buitrago-Bernal, R., & Casallas-Barrera, J. O. (2024). Fluid dynamics of life: exploring the physiology and importance of water in the critical illness. Frontiers in medicine, 11, 1368502. https://doi.org/10.3389/fmed.2024.136850
Welsh, C. & Prentice-Carver, C. (2023). Holes Essentials of Human Anatomy & Physiology (15th ed). McGraw Hill 9781307879735