Nut

Mario & Luigi series
Nuts, or more specifically Peanuts are satisfying snacks used by the Mario Bros. during their adventures in Mario & Luigi series. Nuts restore HP to both Mario and Luigi. In Mario & Luigi: Partners in Time, they were replaced by Mushroom Drops.

Mario & Luigi: Superstar Saga
Nuts first appeared in Mario & Luigi: Superstar Saga. Regular Nuts will heal 20 HP for both brothers. Super Nuts, a stronger version, will heal 40 HP to each brother. Ultra Nuts will heal 100 HP to both bros. Max Nuts, just Max Mushrooms and Max Syrup, will heal all HP to both Mario & Luigi.

Mario & Luigi: Bowser's Inside Story
They made a return in Mario & Luigi: Bowser's Inside Story, after the absence. Just like in Superstar Saga, they are able to heal a certain amount to both bros. Regular Nuts heal 20 HP. Super Nuts, the stronger variety, heal 40 HP. Ultra Nuts heal 80 HP, and are the last nuts the players are able to buy in a store. Max Nuts heal 160 HP, unlike all HP in Superstar Saga, and can only be obtained from defeated enemies or ? blocks.