I, like many runners, have always loved the concept of Nuun: a tab you dissolve in your water that gives you all the electrolytes you need without all the sugar, carbs and calories that are in Gatorade or other sports drinks. But the reality of Nuun can be summed up in this picture:
Sorbitol is an sugar alcohol used to sweeten, but it is also known to cause intestinal upset and diarrhea. (prepare for some geek talk) This is due to the fact that Sorbitol is not completely absorbed from the intestines, leaving behind an increased osmolarity. The result is that an increased amount of water is drawn into the intestines, which leads to the need to find a porta potty immediately.
Nuun has finally responded to this problem by switching over to Stevia. Their chief nutritionist explains the switch here. He neglects to mention the key issue with Nuun’s use of Sorbitol. But the result is the same: runner GI systems everywhere REJOICE!