Gluten sensitivity is a real thing. Someone with it can unknowingly eat something with gluten in it, yet still get symptoms. We may not know what causes it, but that doesn’t mean it’s psychosomatic or fake.
Every time a comic artist uses the real name of something they get accused of getting paid for product placement. But if they use fake names they get accused of unnecessary fear.
It’s possible that the genetic modifications introduce a substance to which you’re intolerant, but seems unlikely.