Reishi: Traditional Uses, Human Research and Extract Safety

What is reishi?

Reishi refers to Ganoderma fungi, often labeled Ganoderma lucidum. Products include fruiting-body powders, extracts, spores and teas. The National Cancer Institute^[1] describes Ganoderma as woody fungi growing on trees. Their chemical composition can differ, and we'll discuss this later on in the article.

Traditional use and modern research

Memorial Sloan Kettering^[2] describes reishi's place in the traditional medical systems of China, Japan and Korea. Its current supplements concentrate selected constituents, including complex carbohydrates called polysaccharides. Historical use helps explain interest in the mushroom, but a traditional preparation and a modern extract need not have the same composition or effects.

The National Cancer Institute's historical account^[1] traces Ganoderma to early Chinese materia medica, where it was regarded as a superior tonic associated with longevity and qi. It describes an association with royalty, possibly because wild specimens were scarce. Its reputation joined medicinal use with cultural ideas about a long life.

The symbolism also survives in physical objects. The Metropolitan Museum of Art^[3] holds a Chinese boxwood ruyi scepter shaped as a fungus of longevity, dated to the 17th–18th century. Such gifts expressed good wishes. This cultural meaning helps explain reishi's longevity reputation without establishing a lifespan benefit from supplements.

Which fungus does “reishi” mean?

Species names complicate the history. Kew's 2026 taxonomic account^[4] distinguishes European Ganoderma lucidum from East Asian Ganoderma lingzhi. Older research and labels often used G. lucidum more broadly. Consequently, a familiar Latin name on an old paper does not by itself resolve which fungus a modern product contains.

Why do people take reishi?

Clinical findings vary with the preparation and the condition being studied.

What should the label tell you?

Check three things: the species; the material used (fruiting body, mycelium or spores); and the extraction method plus daily amount. Fruiting body is the visible mushroom, mycelium its growing threads, and spores its reproductive particles. A “polysaccharide” percentage measures carbohydrate compounds using a laboratory method.

A broad extract label does not establish that the product has the same composition as a preparation studied in a trial. In a blend, the total weight includes the other ingredients; it is not the amount of reishi.

What are the risks and interactions?

A four-week trial^[5] gave 1.5 g/day of reishi or placebo to 40 healthy volunteers. It found no significant differences in the measured clotting or platelet tests. That is useful counterevidence to a blanket claim that every preparation impairs clotting, but it does not establish safety when combined with anticoagulants or antiplatelet medicines. Ask your surgical team when to stop your specific supplement before an operation.

MSK also lists dry mouth, constipation, itching, dizziness and insomnia among reported reactions. Liver-injury reports are another reason to avoid treating a “liver support” claim as reassurance.

The Merck Manual^[6] also cautions that reishi could lower blood pressure further when combined with blood-pressure medicines. This is a possible interaction, not a measured risk for every product. If you take those medicines, discuss reishi and any monitoring with your prescriber before adding it.

The science behind reishi

Fatigue, well-being and sleep claims

A 2005 randomized trial^[7] studied Ganopoly, a polysaccharide extract, in 132 people diagnosed with neurasthenia, a condition involving fatigue and nervous exhaustion. Participants received 1,800 mg three times daily or placebo for eight weeks. Among 123 people assessed at the end, 32 of 62 taking Ganopoly were rated more than minimally improved, compared with 15 of 61 taking placebo. Fatigue and well-being measures also favored the extract.

That finding concerns symptoms in this particular patient group. The trial did not establish longer deep sleep, cortisol reduction or treatment of an anxiety disorder. Nine participants were not included in the final assessment, which adds uncertainty.

A 2021 screening study^[8] found no fatigue benefit in ten men who completed a reishi protocol for Gulf War illness. They took placebo, then 1.6 g and 3.2 g daily of a hot-water and alcohol extract, each for one month. Overall symptom severity did not differ between the lower dose and placebo. At the higher dose, the average rose from 35.0 with placebo to 38.5 on a zero-to-100 scale; pain and fatigue comparisons were not significant. The small group, unvalidated symptom scale and fixed treatment order make a firm conclusion about worsening symptoms premature.

Stress and cognition

A 2024 study^[9] assigned 78 female college students to 500 mg or 1,000 mg of a reishi preparation, or placebo, daily for 30 days. The abstract does not specify the preparation sufficiently to identify it as the same material used in the other trials. It reported improvements in fitness and psychological measures, including anxiety and well-being. The abstract does not make the size and comparison of the psychological changes clear enough to establish treatment of an anxiety disorder. The result remains an early finding in this particular group.

A six-week trial in women with fibromyalgia^[10] also tested mood and quality of life, using 6 g daily of powdered fruiting bodies. It found no statistically significant advantage over placebo. Improvements from a group’s own starting point do not establish that the supplement caused them.

A separate six-week pilot^[11] in 42 people with Alzheimer disease found no advantage of reishi spore powder over placebo for cognition, neuropsychiatric symptoms or quality of life.

Cancer supportive care and immune findings

A 2012 pilot^[12] studied 48 women with breast-cancer-related fatigue during endocrine therapy. Twenty-five received spore powder, 1,000 mg three times daily, and 23 received placebo for four weeks. Fatigue and several function scores favored spore powder. On the 0–52 fatigue subscale, where higher scores mean less fatigue, the final averages were 46.78 versus 40.92—a difference of about 5.9 points. Sleep-disturbance and appetite-loss questionnaire scores also favored it; pain, constipation and diarrhea did not show significant differences.

A Cochrane review^[13] included five small randomized cancer trials. Some immune-cell measurements and quality-of-life assessments favored reishi-containing treatment. However, the pooled tumour-response estimate was uncertain: its confidence interval included no difference, and no included trial recorded long-term survival.

Immune-cell changes do not establish that a supplement prevents infections or improves chemotherapy tolerance. Preparations and accompanying treatments varied. Cancer supportive care is a separate question from using reishi alone to treat cancer, and either use needs discussion with the oncology team.

A later 2020 trial^[14] enrolled 82 people receiving chemotherapy for non-small-cell lung cancer. A reishi-and-privet formula, 3.36 g daily for six weeks, did not significantly improve the main lung-cancer quality-of-life score compared with placebo. Because this was a combination, it also cannot isolate an effect of reishi.

Colorectal adenomas

A 2010 controlled study^[15] examined MAK, an extract from the medium used to culture reishi mycelium. Participants took 1.5 g daily for a year. Of 123 people enrolled in the treatment group, 96 completed follow-up; researchers compared them with 102 untreated patients. Adenoma number and total size fell in the treated group and rose in controls.

This was not random allocation to treatment and placebo, and the losses from the treated group matter. The finding concerns adenomas, not demonstrated prevention of cancer or improved survival, and MAK is a different preparation from ordinary mushroom powder.

Urinary symptoms

An 88-man trial^[16] enrolled men over 49 with slight-to-moderate urinary symptoms and tested 6 mg daily of a specific ethanol extract for 12 weeks. The International Prostate Symptom Score^[17] runs from 0 to 35, with higher scores indicating worse symptoms. The difference favored the extract by 1.18 points (95% confidence interval 0.62–1.74 points). That is a small shift on the scale; the abstract does not say how many men noticed meaningful relief. Quality of life, urine flow, residual urine, prostate size, the prostate-related blood marker PSA, and testosterone did not differ.

Blood sugar and cardiovascular risk

In a 2016 randomized trial^[18], 84 participants with type 2 diabetes and metabolic syndrome received a daily Ganoderma preparation providing about 3 g of extract and spores, the preparation plus cordyceps, or placebo for sixteen weeks. The researchers combined the active groups for analysis after recruitment fell short. The combined reishi-treated participants did not improve blood glucose or other measured cardiovascular risk factors compared with placebo. Pooling means this is not a precise separate estimate for reishi alone, but it supplies no positive evidence for either tested strategy.

A 2026 trial^[19] in sixty patients used 250 mg of a different preparation three times daily for eight weeks. It contained linked carbohydrate and protein-related material and found no advantage for its inflammatory markers, lipids or body-mass index. These results concern the preparations tested; spore oil has produced a different finding.

A 2025 trial^[20] enrolled 110 people with abnormal blood lipids and reported lower triglycerides, total cholesterol and LDL cholesterol, and higher HDL cholesterol, with reishi spore oil than placebo after 12 weeks. This positive result should be considered alongside the negative extract trials. The abstract does not say how large the lipid differences were, limiting how much practical benefit can be inferred.

Liver research

A 2017 crossover study^[21] in 42 volunteers used six-month treatment periods separated by a month without treatment. Its abstract reports improved antioxidant measurements and liver enzymes with a preparation enriched in several mushroom constituents, but does not provide a clear numerical between-group effect. Its ultrasound illustrations show two participants whose mild fatty-liver appearances improved. These limited observations do not establish a treatment for fatty-liver disease, and they coexist with liver-injury case reports involving other reishi products.

MSK^[2] also distinguishes laboratory activity from limited clinical evidence. Reishi is not an alternative to prescribed cancer or diabetes treatment.

Bottom line

Reishi's human findings depend on the goal and preparation. A fatigue trial and some cancer-support studies offer preliminary signals, while metabolic findings differ between extracts and spore oil. Urinary symptoms and colorectal adenomas have also been studied, with important limitations; a small Alzheimer trial was negative. Review anticoagulants, immune-suppressing treatment and liver concerns before using an extract.

Help us improve this article

Spotted an error or found a source we should consider? Tell us which part of this article needs another look and include a link if you have one. Please leave out personal health details and lab results; we can’t answer individual medical questions.

Your name

Email address

What would you like to share?Select a topicCorrectionSource or research suggestionArticle requestAccessibility issueBusiness inquirySomething else

Your message

Continue to email →Email us directly