Low electrolytes can contribute to fasting headaches, it follows that boosting your electrolytes can help prevent headaches while fasting. The main electrolyte to focus on is sodium (aka salt),  because that’s the most plentiful one in your bloodstream, and the one that helps maintain your blood pressure. For most people, a few extra grams of sodium per day will do the trick. (1 gram = 1,000 milligrams.) Potassium and magnesium are the two other electrolytes that are often worth supplementing while fasting.