During all your fasts, but especially during your longer fasts, it’s important to make sure you’re staying properly hydrated, not just with water but also with electrolytes. Typically, water and fresh, hydrating fruits and veggies provide all the electrolytes you need. But when you’re fasting, eating low-carb, and especially if you’re exercising or live in a hot, humid climate, you may need to supplement with additional electrolytes.
This is because you lose electrolytes through your sweat (in every liter of sweat, you lose 900 mg of sodium, 15 mg of potassium, and 13 mg of magnesium). Also, a low-carb diet cuts out inflammatory carbohydrates, which can result in water loss, throwing off your electrolyte balance.
Excerpted from MBG Health