Do athletes need more salt than standard sodium advice suggests?
For heavy or salty sweaters doing long, hot sessions, yes — sweat sodium losses can be far higher than general low-sodium guidance assumes. The bigger danger, though, is drinking more fluid than you lose without replacing any sodium, not simply undersalting.
“Eat less sodium” is public-health advice aimed at a specific problem: long-term blood pressure and cardiovascular risk in a mostly sedentary population. It’s why the Dietary Guidelines cap sodium around 2,300 mg a day. That number was never built with someone who sweats through a three-hour trail run or back-to-back summer practices in mind, and for that person, the cap can undersell what their body is actually losing.
Sweat sodium concentration also varies enormously between people, roughly 10 to 90 mmol/L (about 230 to 2,070 mg per liter of sweat), depending on genetics, heat acclimation, fitness, and diet, not effort. A “salty sweater” crusted in white residue after a workout can lose several times more sodium per liter than a training partner doing the identical session. Stack that onto a few hours of sweating in the heat, and the total loss for some athletes lands well above what general guidance allows for an entire day.
Why the general rule doesn’t fit here
That’s the gap the standard advice misses, and it’s why sport-specific guidance looks so different. The ACSM has long recommended 0.5-0.7 g of sodium per liter of fluid for exercise beyond an hour, partly because it helps you retain what you drink. The ISSN’s ultramarathon position stand goes further for heat and ultra-distance events: 500-700 mg/L, climbing toward 300-600 mg per hour, figures that would look reckless on a general nutrition label.
The bigger risk is water, not salt
Exercise-associated hyponatremia is real and has killed marathoners, but the 2017 consensus update on it is blunt: the main driver is drinking more than you lose, not skimping on salt. Sodium-containing drinks do hold plasma sodium steadier than plain water when intake matches sweat losses, but the same trial found no clear benefit against cramping. Sodium supports a sound drinking plan; it doesn’t rescue you from a bad one.
If you’re a light-to-moderate sweater training an hour or less, normal food and thirst-driven drinking are still enough. If you sweat heavily, taste salt on your skin, or train long in heat, get a sweat test, or at least track your own salt crusting and cramp history, and build sodium intake around your own numbers instead of either one-size-fits-all rule.