It's probably just a phase, teething, a wonder week, etc. If it doesn't pass in a week or so, you may want to move her bedtime a little later. My daughter use to go down at 6:30, and then around 10 months or so it changed to 7, and now, at 19 months, we are close to 8. I had to keep pushing it back later because she was waking up earlier, and earlier. I tried putting her down earlier and she just woke up earlier! Sleep does beget sleep for some kids, and then there are others that just do not need as much sleep. My daughter doesn't really need much more than 10.5 a night. She wakes up happy, is happy all day, etc. so as much as I'd love to have a toddler that slept 12-14 hours a night, I've accepted that she isn't one. I have a friend whose daughter is similar in her sleep to mine: they are just too busy to sleep, and since their moods don't suffer for it, we don't worry about it.
I doubt it has anything to do with food.