Livestrong.com recommends cutting gluten out of your diet as one way avoid triggering schizophrenia:
"Mental illness often produces a sensitivity to gluten, which can result in many of the symptoms of schizophrenia. Eliminating gluten sources from your diet will reduce these issues. Gluten is present in foods that contain wheat, rye, barley and their byproducts. Read labels to be sure you are completely avoiding foods that aren't gluten-free. Common foods you will need to avoid include bread, crackers, many cereals, soy sauce, baked goods, beer and some other alcoholic drinks (Link).
Livestrong also recommends avoiding candy and other processed sugars, while adding a good multivitamin and Omega 3 supplement into your diet.
Dr. Mercola points out on his website that there is "60 Years of Research Links Gluten Grains to Schizophrenia" (Link)
One lady who suffered from schizophrenia said that the following foods triggered her schizophrenia.
Here are some of the foods that she found triggers her schizophrenia:
1) Fats are the very very worst. When I over eat fats the voices literally scream at me.
2) Bread [Gluten]
4) Preservatives (Link)