Where do cruise lines source their food ingredients?

This might be a strange question, but does anyone know where cruise lines source their food ingredients from? For example, does a cruise sailing the Mediterranean source most of their food from Europe? I am sailing NCL this summer on the Mediterranean. I am an American and have pretty high sensitivities (rashes, hives, joint immflamation)to certain foods here, particularly wheat and gluten, assumingely from the pesticides and things that we used to grow our wheat here (I am not celiac). However when I am in Europe, I am able to eat whatever I want with no issues. It would be so nice to be able to eat freely on the cruise, but not sure where their ingredients are sourced from. Obviously, this would mainly be things like flour, breads, pastries, pasta, etc. Europe has much stricter food regulations, do cruise lines have to follow local guidelines? Thank you!