(This is Rule #6 in our periodic series, “The 25 Golden Rules of Running: proven, time-tested rules of running that have worked for thousands upon thousands of runners over the miles.)

Don’t eat or drink anything new before or during a race or hard workout.   This makes sense.  At times of stress and great importance on what you put in your body, put things that you know will be easy to digest, will be familiar and comfortable in combination with your body’s digestion and needs, and will be less likely to come back on you in unhappy ways. 

Stick to what works for you. “Your gastrointestinal tract becomes accustomed to a certain mix of nutrients,” says Dallow. “You can normally vary this mix without trouble, but you risk indigestion when prerace jitters are added.”

The Exception: If you’re about to bonk, eating something new is probably better than eating nothing at all.  And have a great run!