The Healthspan Map · Nutrient

Water

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.
Nutrient or lever	Direction	Strength	Evidence type	What was found	Source
Water	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)
Water	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)
Water	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)
Water	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)
Water	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)

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.
Nutrient or lever	Direction	Strength	Evidence type	What was found	Source
Water	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)
Water	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)