Sodium, potassium, chloride, calcium and magnesium carry electrical charge. Kidneys keep their blood levels in tight ranges.
Sports drinks
Useful for long, sweaty exercise; for everyday activity water and food usually provide enough.
Too much water
Drinking far more water than you lose during long events can dilute sodium dangerously (hyponatremia).
Evidence & sources
Exercise-associated hyponatremia can occur when endurance athletes drink fluid in excess of losses. Evidence: strong. Known: Consensus statement. Unknown: Individual sweat rates vary widely. Source: Hew-Butler et al., Clinical Journal of Sport Medicine, Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference (2015).