reishi

Reishi (Ganoderma lucidum, also called lingzhi) is a mushroom long used in traditional Chinese medicine and now sold in the US as a dietary supplement—commonly as capsules, powders, extracts, or teas. As with other dietary supplements, the FDA does not review or approve reishi products for safety or effectiveness before they reach the market.

Neither of the authoritative US government resources reviewed (NCCIH and MedlinePlus) publishes a fact sheet specific to reishi, and well-designed human studies are limited. Speaking more broadly about Chinese herbal products, NCCIH states that many studies have been of poor quality, so no firm conclusions can be drawn about their effectiveness. Marketing claims that reishi treats, prevents, or cures cancer, infections, or any other disease are not supported by these sources, and supplements may not legally be sold with claims to treat disease.

There is no established or government-recommended dose of reishi, and the amount of active compounds can vary from product to product. Do not exceed the amount on the product label, and speak with your doctor or pharmacist before starting reishi—particularly if you are pregnant or breastfeeding, have a medical condition, or take any medications.

Reishi is sold as a supplement, not a regulated drug, and does not go through the testing that prescription medicines do—so quality and purity can differ between products. NCCIH cautions that some Chinese herbal products have been found to contain things not listed on the label, including undeclared drugs, heavy metals (such as arsenic, lead, and cadmium), pesticides, or the wrong herbs—and that some incorrect herbs have caused organ damage. Choose products carefully and tell your health care provider about any supplement you take. As NCCIH notes, "natural" does not necessarily mean safe.

The authoritative US government sources reviewed do not publish a reishi-specific list of side effects, so its full safety profile in people is not well characterized. As a general precaution, stop use and seek medical advice if you notice any reaction—such as digestive upset, a rash, or other unexpected symptoms—and report problems to your health care provider.

The cited US government sources do not describe reishi-specific drug interactions, so its interaction profile is not well characterized. As a general matter, NCCIH and MedlinePlus warn that supplements and medicines can interact in unexpected ways. To be safe, talk to your doctor or pharmacist before combining reishi with any prescription medication or before any surgery.