Reishi

What it is

Reishi (Ganoderma lucidum and close relatives) is a shelf-shaped fungus with a hard, woody, often kidney-shaped cap and a glossy, lacquered surface that ranges from red-brown to nearly black. In China it's called lingzhi. Several related Ganoderma species grow on hardwoods and conifers in North America, and growers in the US cultivate reishi for teas, powders and extracts.

Reishi is not a cooking mushroom. It's tough and bitter, and people use it as a dried, sliced or powdered ingredient in teas and extracts.

Traditional use

Reishi has a long history in East Asian traditional medicine. According to Memorial Sloan Kettering Cancer Center's integrative medicine service, it is used in many Asian countries to increase energy, support the immune system and for general health. Modern supplement marketing extends those claims further, to stress, sleep, cholesterol and cancer support.

Traditionally it's prepared as a long-simmered tea or decoction from dried slices. Commercial products include capsules, powders, tinctures and spore products.

How it's grown

Growers cultivate reishi on hardwood logs or bags of supplemented sawdust. Depending on how much fresh air it gets, the fungus forms either the classic flat shelf or long, branching "antler" shapes. Harvested pieces are dried before sale. The resulting product depends heavily on the grower and processor, since extracts, mycelium products and fruiting-body products are not the same thing.

Storing it

Dried reishi keeps for a long time in a sealed container away from heat, light and moisture. Discard anything that shows mold or smells musty. Follow the manufacturer's storage directions for extracts and capsules.

Where to buy reishi

6 growers in our directory list reishi by name@if ($ohio->isNotEmpty()), 2 of them in Ohio. Availability changes with the season and the harvest, so check with the farm before you go.

Does the science say…?

Much of the excitement about reishi comes from laboratory and animal studies. Human evidence is limited.

• Cancer. A 2016 Cochrane review of randomized trials found that the trials were generally of poor methodological quality and concluded there was not enough evidence to justify reishi as a first-line cancer treatment. Some trials reported better tumor response when reishi was added to chemotherapy or radiotherapy, and modest changes in immune measures, but the reviewers said it remains uncertain whether reishi helps long-term survival (Jin et al., 2016).
• The US position. The National Cancer Institute's summary of medicinal mushrooms states that the FDA has not approved medicinal mushrooms to treat cancer or any other medical condition.
• Safety. Memorial Sloan Kettering reports cases of liver injury linked to powdered reishi, including one death, and warns that reishi may increase bleeding risk in people taking blood thinners and may not be safe for people taking immunosuppressant drugs.

If you're curious about reishi, talk with your doctor or pharmacist first, especially if you have a medical condition, take prescription medication, or are being treated for cancer. The NIH's National Center for Complementary and Integrative Health has a practical guide to using supplements wisely.