Why are some raw food, like fish, safe to eat while others are not?

Fish guts: Contain an enzyme called thiaminase that desroys vitramin b1. In some counries they make a fish patois that includes the whole fish. This may be responsible for the disease known as bangungut, or "toxic dream" that is lethal. The japanese, however, make sushi that is white rice associated with the muscular part of the fish and it is safe when eaten at a japanese restaurant. Veggies and fruit O.K.