Bromelain, a chemical substance found in the stem and juice of pineapple, is extremely effective as it is believed to improve lung function, and help to loosen mucous. With a history of alternative medicinal use, bromelain is a complex mixture of protein-digesting enzymes, commonly believed to reduce inflammation related to infection. While pineapple is a major dietary source, it does not provide a medicinally-effective dosage of the substance. Nonetheless, pineapple is a wholesome addition to any diet and it can play a key role in maintaining good health.