My favorite tuna salad recipe uses Granny Smith apples and very little mayonnaise. Add about 1/2 of an apple to a can of tuna. You can decide on the proportions you like. The moisture from the apple means you only need to add 1-2 tablespoons of mayonnaise. Add some dill, a little green onion, and a splash or two or three of hot sauce (I use Texas Pete).