I think it really helps to nibble on SOMETHING during labor. I had natural waterbirth last pregnancy, so I of course didn't have to deal with hospital regulations not allowing me to eat but I found it so helpful. I had a little beer, and some saltines (might sound gross to some of you, but hey, it helped me). Salty food like crackers, chips, nuts can really alleviate some of the nausea. I'm giving birth at a hospital this time around (not my choice) and my awesome midwife told me that she secretly lets her patients have food during labor and doesn't give a rip what the hospital thinks- I love her.
Anyway- avoid hunger, or don't go into labor hungry, is my advice!
I'll definitely had the old stand by saltines and ginger and peppermint teas. I'm going to talk to my midwife about it when I see her Wednesday.