From the Super Mario Wiki
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The Life-Up Heart is a power-up item that appears in Super Mario Odyssey. It is the only "traditional" power-up in the game, as Mario's forms are mostly taken through Cappy's Capture ability. It serves the same function as the Life Mushroom from Super Mario Galaxy and Super Mario Galaxy 2: when collected, it increases Mario's maximum health to six (nine in Assist Mode); however, if his health is depleted back to three (six in Assist Mode), he loses the three extra pieces of health until another Life-Up Heart is obtained. If the player collects a Life-Up Heart at maximum health, it grants 10 coins instead. Life-Up Hearts can be purchased from the Crazy Cap store for 50 regular coins, won from slot minigames, and found in ? Blocks. Only one Life-Up Heart appears in 2D: In the Metro Kingdom's Projection Room, the 2D Life-Up Heart is found where the Hidden Block is in the original Super Mario Bros.
Crazy Cap description
"This heart-shaped item raises your maximum life value."
Names in other languages