Ultramarathon runners who drank only when thirsty and skipped salt pills during a long, hot race lost about 3.4% of their body weight — and experts say that’s still a safe level of hydration.

Ultramarathon runners who take sodium supplements during long races in extreme heat keep more of their body weight, but those who skip the supplements might actually stay better hydrated, according to the researchers.

Ultramarathon runners who took more sodium during a super long, super hot race tended to lose less body weight — the more sodium they took, the less weight they lost.

Endurance runners in a super long, hot race who took sodium supplements every part of the way lost less body weight during the race than those who didn’t take any.

Endurance cyclists who take in 700 mg of sodium per hour during a 3-hour ride in cool weather tend to drink about 160 mL more fluid each hour than those who don’t — probably because the salt affects how thirsty they feel.

Even if endurance runners take a lot of salt pills during long races, drinking too much water — like 10 liters — can still give them a dangerous condition called low blood sodium. Salt alone won’t protect you if you’re chugging way too much water.