Initial Posting: 2/13/2016    Last Update: 8/10/2019
Answer: Reishi (Ganoderma lucidum) is an edible mushroom traditionally used in Chinese medicine for a wide range of purported health benefits, such as increasing vitality and strengthening the heart. In the U.S., supplements containing reishi are most commonly promoted for "strengthening" the immune system, as well as for lowering blood sugar, improving cardiovascular function, protecting from liver damage and reducing cancerous tumors.
Compounds in reishi, including certain beta-glucans and ganoderic acids, are thought to be responsible for some of its benefits. However, evidence from clinical trials has been mixed, and one clinical trial in people with gastrointestinal cancer found that taking reishi had negative effects. For details, information about potential safety concerns and side effects, plus our tests and Top Pick among popular products, see the Reishi Mushroom Supplements Review.