Reishi Mushroom (Ganoderma lucidum): Compounds, Forms, Studied Amounts and Safety

Reishi is the Japanese name for Ganoderma lucidum, known in China as lingzhi, the "herb of spiritual potency". Lucidum means shiny, after the varnished cap. It is a large, dark, woody mushroom, so it is taken as a powder, tea or extract rather than cooked as food.

Where it grows

The species does best in hot, humid conditions, and many wild varieties come from the subtropical regions of East Asia. The wider Ganoderma genus is found worldwide in several colors. Black reishi is popular in South China, while red is preferred in Japan.

Cultivated versus wild

Wild reishi is scarce, and cultivation has been the main source since the early 1970s, on substrates such as grain, sawdust, wood logs and cork residues. Fruiting bodies take months to form, so producers increasingly grow mycelium in tanks for a steadier supply. One analysis detected lead, cadmium and mercury in log grown fruiting bodies, a reason to test any reishi ingredient for heavy metals.

Hot water, alcohol and dual extracts

Hot water draws out polysaccharides, including beta glucans. Triterpenes are normally extracted with alcohol. A dual extract runs both steps and combines them. A label that says only "extract" leaves the method unknown.

What an extract ratio does and does not tell you

A ratio such as 8:1 means roughly 8 kg of dried mushroom went into 1 kg of extract. It says nothing about the part of the fungus, the solvent, or how much beta glucan or triterpene the extract holds, so two 8:1 extracts can differ a great deal. It also means gram amounts from studies of whole mushroom preparations cannot be compared directly with a milligram amount of extract.

Small, short trials have usually reported few or no side effects. WebMD rates reishi extract as possibly safe for up to one year and powdered whole mushroom for up to 16 weeks.

Reported side effects

Monographs list dizziness, vertigo, dry mouth, nausea, upset stomach, constipation, itching, rash and trouble sleeping. Autoimmune skin conditions have also been reported to start or flare, though a cause has not been established.

Liver injury reports

LiverTox, the National Institutes of Health liver injury database, rates reishi a possible rare cause of clinically apparent liver injury (likelihood score D). It describes a few case reports from China, Japan, Thailand and India, mostly with powdered products, including one fatal case of sudden liver failure linked to reishi powder. Injury usually began 1 to 2 months after starting, and recovery was complete within 1 to 3 months of stopping. Other causes were often not fully excluded, and trials have not shown raised liver enzymes.

In the US, reishi is sold as a dietary supplement under the Dietary Supplement Health and Education Act of 1994 (DSHEA), which counts herbs and other botanicals as dietary ingredients. FDA does not approve supplements before they are marketed. The maker or seller is responsible for safety and labeling, and FDA can act against an adulterated or misbranded product once it is sold. Structure and function statements must carry the FDA disclaimer shown at the bottom of this page.