During fasting, the body excretes more sodium — and with it potassium and magnesium. Research by Phinney shows this is most pronounced in the first days as insulin drops. Symptoms people blame on “not eating” are often just low electrolytes. For short fasts, most don’t need supplementation; for longer fasts, adding sodium, potassium, and magnesium prevents headaches, fatigue, and cramps.
This companion covers what happens during fasting, depletion symptoms, when and how to supplement. (3 min read)