Papaya is a plant. Its leaves and fruits are used to make medicine. Papaya contains a chemical called papain, which is commonly used as a meat tenderizer. Papain breaks down proteins, carbohydrates, and fats. Papaya also contains a chemical called carpain. Carpain seems to be able to kill certain parasites, and it might affect the central nervous system. Papaya also seems to have antibacterial, antifungal, anti-inflammatory, antioxidant, and immune-stimulating effects.