As has been said, they'll accommodate most dietary needs once you get the proper chit, whether it's for gluten intolerance, religious beliefs, etc. Let the candios know as soon as you can, maybe they can make arrangements to get you some more appropriate meals instead of those box lunches (AKA "bag nasties"), which are basically exactly as 44magnum described. If not, you'll be eating nothing but the cold cuts from the sandwiches and an apple for quite a few meals that first week. Although I'm sure apples won't be in short supply. In the same vein, if it's something medical, let your class team know, they might allow you some supplements. Their first priority is your safety. However hard that may be to believe when you're gasping for breath in the SUYA.
Just saw the word "probiotics." Don't worry, they have plenty of that Jamie Lee Curtis yogurt in the chow hall.