It's true whether you believe it or not. Pineapple contains an enzyme called bromelain, which is a little-known fact. If you read other sources, you'll notice that they all say pretty much the same thing. This enzyme degrades proteins in your mouth, specifically your taste buds. This can ruin your palate for the rest of the day until your mouth heals. A fun fact that many people believe is that the enzyme bromelain is used in meat tenderizer. Pineapple is a fruit, so it's good for you. However, you should let a freshly sliced pineapple sit in the fridge for a few minutes before eating it so the enzymes can break down.