Used medicinally in China and Japan for over 4,000 years, the reishi mushroom (Ganoderma lucidum) is purported to have anticancer and immune-boosting properties. Also known as mannentake or artist's conk, it is widely distributed around the world. A woody-textured fungi, its stem and cap are white or yellow when young, darkening to reddish brown or black over time.
Reishi mushrooms contain polysaccharides (beta-D-glucans) and triterpenes (ganoderic and ganoderenic acids). Other medically significant ingredients include sterols (ergosterol) and coumarin.
Supplements typically contain standardized dosages of at least 4 percent triterpenes and 10 percent polysaccharides. In addition to medicinal components, mushrooms contain potassium, B-vitamins and fiber.
Reishi mushrooms are simmered in water to release their active ingredients. Raw, the mushroom is tough and unpalatable. Often, reishi is sold dried in supplement form, although teas and tinctures are also available.
Reishi mushroom supplements are used as an adjunct to traditional cancer therapies such as radiation and chemotherapy. According to the Abramson Cancer Center of the University of Pennsylvania, reishi can "stimulate the immune system ... increase the activity of standard cancer treatments (chemotherapy and radiation therapy) and help decrease the side effects of these therapies."
Additionally, reishi has, in laboratory tests, displayed tumor-suppressing potential and anti-inflammatory qualities. According to the Myrna Brind Center of Integrative Medicine, reishi has shown "beneficial effects on transcription factors as well as inhibiting migration of highly invasive prostate and breast cancer cells."
According to Dr. Cathy Sabota, Horticulture Specialist at the Alabama Cooperative Extension, other possible uses for reishi include migraine headache relief, gout and rheumatism pain reduction, blood pressure regulation and respiratory benefits.
High does of reishi can cause diarrhea and a drop in blood pressure. Always purchase mushrooms from a reputable source; do not harvest mushrooms from the wild.