The Healthspan Map · Nutrient

Water

Compiled by Aamir Malik, PhD, Professor of Neuroengineering at Brno University of Technology, from published studies. He is a researcher, not a physician. Last updated 21 August 2026.

Linked to getting too little

Where a shortfall of Water is linked: 5 sources.In the order the Map holds them: strongest evidence first. That is a statement about the evidence, not about what matters most.
Condition or system	Direction	Strength	Evidence type	What was found	Source
Balance & falls risk	Eat enough of	Moderate	Established clinical	Dehydration promotes orthostatic hypotension and dizziness, raising fall risk.	Falls in cardiovascular disease (AHA statement) (opens in a new tab)
Brain fog & memory	Eat enough of	Strong	RCT / trial	Mild dehydration (~2%) impairs attention, immediate/working memory and reaction time.	Ganio et al. 2011, Br J Nutr (opens in a new tab)
Chronic fatigue / low energy	Eat enough of	Moderate	Cohort / observational	Mild dehydration at rest increased fatigue/inertia and impaired concentration.	Mild dehydration & mood/fatigue study (Br J Nutr) (opens in a new tab)
Headache & migraine	Eat enough of	Strong	RCT / trial	Regular increased water intake reduced headache burden; dehydration is a well-established headache trigger.	Spigt et al. 2012, Fam Pract (opens in a new tab)
Liver, Kidney & Urinary	Eat enough of	Strong	RCT / trial	Adding ~1.5 L water/day cut recurrent UTIs by 48% (RCT) and halved kidney-stone recurrence.	Increased water intake & recurrent UTI (Hooton RCT, PMC6584323) (opens in a new tab)

Linked to getting too much

Where an excess of Water is linked: 2 sources.In the order the Map holds them: strongest evidence first. That is a statement about the evidence, not about what matters most.
Condition or system	Direction	Strength	Evidence type	What was found	Source
Brain fog & memory	Don't overdo	Moderate	Established clinical	Early water intoxication causes confusion and impaired concentration before progressing to seizures.	Water-intoxication literature (opens in a new tab)
Neurological & Mental Health	Don't overdo	Strong	Established clinical	Overhydration (drinking faster than the kidneys can excrete, ~0.8-1 L/hour) dilutes blood sodium -> hyponatremia/water intoxication: headache, nausea, confusion, seizures, cerebral edema, coma and death. Seen in endurance athletes and psychogenic polydipsia. (Directly connects to the Sodium deficiency row.)	Water-intoxication systematic review (opens in a new tab)

The Healthspan Map is part of Fix the Floor, a book by Aamir Malik. About the book