Diarrhea and Fasting: When to Break Your Fast for Gut Health

When fasting, managing electrolyte intake is essential, but an imbalance—whether too much or too little—can cause discomfort, particularly in the form of diarrhea. Both ends of the spectrum, overconsumption and underconsumption of electrolytes, can trigger digestive issues that may derail a fasting experience.

One common cause of diarrhea during fasting is consuming excessive amounts of electrolytes, particularly magnesium. While magnesium is essential for many bodily functions, too much can have a laxative effect, leading to unwanted trips to the bathroom. On the other hand, insufficient electrolytes, such as sodium, potassium, and magnesium, can also disrupt digestion. When the body lacks sodium, for instance, it may respond by releasing stored water, leading to dehydration-related diarrhea.

To avoid these issues, aim for balanced electrolyte intake. Dr. Jason Fung and Dr. Mindy Pelz recommend a moderate approach to sodium intake, especially as the body releases stored water when glycogen is depleted during fasting. Generally, 1 to 2 grams of sodium (about half a teaspoon of high-quality salt) per day can help maintain hydration and balance. Magnesium is beneficial for muscle and nerve function but should be limited to around 200-400 mg per day to avoid laxative effects.

During a fast, if you experience diarrhea, check your electrolyte levels. If they’re too high, reduce the intake, especially of magnesium. If they’re too low, consider adding a pinch of salt or an electrolyte supplement without excessive magnesium. Remember, individual needs vary, so listen to your body and adjust accordingly.