Sweat Replenishment: What You Actually Lose in Sweat

Everyone knows sweat is salty. Fewer people know what else leaves with it, and that gap shapes how most hydration products are built: as salt-replacement tools and not much more.

The full inventory of sweat

Sweat is mostly water, with sodium and chloride as the dominant minerals. But it also carries potassium, and smaller amounts of calcium and magnesium. Concentrations vary widely between individuals and with heat acclimation, which is why two athletes finishing the same workout can have very different replacement needs.

A single session’s calcium and magnesium losses are modest. The issue is accumulation: heavy training weeks layered on top of diets that already fall short of recommended intakes for both minerals.

When water alone covers it

For light sessions under an hour, plain water and your next meal usually handle replenishment fine. The body is good at this when losses are small.

Long sessions, hot conditions, double days, or visible salt lines on your clothing are the signals that fluid plus minerals beats fluid alone.

Replenishing well

• During: drink to thirst; add sodium for sessions over an hour or in heat.
• After: restore fluid and the complete mineral profile, not just salt.
• Daily: keep calcium and magnesium topped up so training losses are not stacking on a deficit.
• Skip the sugar: replenishment does not require a sugar crash on the way out.

This is the thinking behind N-2’s formula: 550 mg of sodium for what sweat takes out, balanced with 130 mg each of calcium and magnesium, 200 mg of potassium, and 70+ marine-sourced trace minerals, with no added sugar. Sweat replenishment, treated as a mineral problem instead of just a salt problem.