http://www.ratfanclub.org/diet.html
Forbidden Foods
Generally, if you would eat a food, you can give it to your rats. Here are some exceptions and notables:
raw dry beans or peanuts—contains antinutrients that destroy vitamin A and enzymes needed to digest protein and starches, and causes red blood cells to clump
raw sweet potato—contains compounds that form cyanide in the stomach
green bananas—inhibits starch-digesting enzymes
green potato skin and eyes—contain solanine, a toxin
wild insects—can carry internal parasites and diseases
raw bulk tofu—can contain bacteria, packaged raw tofu is safe
orange juice—forbidden for male rats only, d-limonene in the skin oil, which gets into the orange juice during squeezing, can cause kidney damage and kidney cancer due to a protein that only male rats have in their kidneys. Pieces of the orange fruit are okay if you wash the orange-skin oil off of it after peeling it.