Reishi Mushroom, also known as Ganoderma lucidum, is a mushroom that grows in hot and humid areas throughout Asia and has been a common staple of Eastern medicine for centuries. In more recent years, Reishi has become a popular supplement due to its ability to support immune health and to reduce feelings of fatigue. The benefits of Reishi are attributed to numerous beneficial ingredients including triterpenoids, polysaccharides, and peptidoglycans.