You're asking and I'm answering.
"Fit. I've recently started running but I've noticed an unpleasant side effect. A few times I've had to get off the treadmill and run to the bathroom. It's totally embarrassing to me; please tell me it's normal."
—Running to Restroom
Great question and I love when readers pose slightly embarrassing questions because it always provides a small sigh of relief for everyone to read it and say, "I'm not alone." Needing to go is a very common issue among runners; let's just say that the abundance of port-o-potties at marathons are not for the spectator's use.
Here is the thing: The up and down motion of running can irritate the intestines and make us have the urge to go. When I first started running I had this very same problem, and I know that having to stop halfway through a run can be very discouraging to someone trying to build up endurance. For an expert's advice on how to deal I turned to WedMD:
Gastroenterologist David Bjorkman, MD, dean of the University of Utah School of Medicine, recommends eating at least two hours before a run. Caffeine can speed the movement of wastes through your system, and artificial sweeteners (such as mannitol and sorbitol), which are often found in energy bars, can cause GI distress. Although it's not wise to have a bran muffin before a race, Dr. Bjorkman says to incorporate more fiber in your diet (work up to 20 grams a day). "Adding fiber can make you more regular. You can get your system to operate like clockwork, so that you can reliably go before a run."
From my own experience all of the above holds true, but I've also found that timing is critical. For example, if you typically hit the restroom first thing in the morning, then an a.m. run may not be the best option. Also, it's a good idea to always try to use the bathroom before you run.
You're definitely not alone and hopefully, with a little tweaking of your diet and timing, the only urge you'll feel is to run longer.