Sodium Chloride (USP)

Sodium chloride — table salt, in pharmaceutical-grade form — is the dominant extracellular electrolyte in the human body and the primary driver of fluid retention, blood volume, and nerve impulse transmission. During exercise, sweat sodium losses are substantial and highly individual, and replacing it matters for both performance and for avoiding dangerous hyponatremia. The evidence for sodium's rehydration role is consistent: drinks with higher sodium concentrations improve fluid retention by around 36% compared to plain water, reduce urine output by roughly 60%, and increase voluntary fluid intake through heightened thirst drive. For performance directly, the picture is more mixed — multiple endurance trials found sodium supplementation during races did not improve finish times versus placebo, though pre-exercise sodium loading has outperformed glycerol hyperhydration for plasma volume expansion in some protocols. Endurance athletes exercising in heat or for more than 60–90 minutes are the clearest candidates for deliberate sodium supplementation. Excessive intake is linked to hypertension; people with cardiovascular or kidney disease should stay within medically advised limits. The world's most unglamorous supplement, doing the most fundamental job.